Economic Potential of High Density Data Storage Implemented
by Patterned Magnetic Media Technology
By
MASSACHL.•ETTS INSTITUTE
OF TECHNOLOGY
Lei Du
SEP 12 2008
B. Eng. Materials Engineering
Nanyang Technological University
LIBRARIES
SUBMITTED TO THE
DEPARTMENT OF MATERIALS SCIENCE AND ENGINEERING
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF ENGINEERING IN MATERIALS SCIENCE AND ENGINEERING
AT THE
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
SEPTEMBER, 2008
© 2008 Massachusetts Institute of Technology
All right reserved
Signature of Author....... .--
Department of Materials Science and Engineering
August 15, 2008
.-.......---..... . .........
Caroline A. Ross
Professor of Materials Science and Engineering
Thesis Supervisor
C ertified by.............................................................................................
Accepted by ............................................
...-------.........-Samuel M. Allen
POSCO Professor of Physical Metallurgy
Chair, Departmental Committee on Graduate Student
9E8Wws
Economic Potential of High Density Data Storage Implemented
by Patterned Magnetic Media Technology
By
Lei Du
Abstract
Hard drive industry is facing scaling challenge for areal density to be further increased.
This is due to the triangular conflictions among thermal stability (superparamagnetic
effect), single-to-noise ratio and writability of the recording media. One of the most
promising methods to overcome this constraint is the patterned magnetic media
technology. Although it is facing many challenges, the large potential gains in density
offered by patterned media make it one of the possible milestones on the horizon for
future of the disk drives industry. One of the biggest challenges for patterned media is to
realize its mass fabrication provided reduced cost per bit. The basic fabrication approach
is to use lithography to pattern the magnetic materials on the platter. However, patterned
media requires well-ordered nanoarrays with dimensions less than 25 nm, which
challenges the state-of-art lithography technologies.
This M. Eng. project focuses on evaluations of the technologies and fabrication schemes
potential for patterned media from various aspects like technical barriers, cost and
intellectual properties. Technologies including E-beam lithography, nanoimprint
lithography, templated diblock copolymer self-assembly and self-assembled magnetic
nanoparticles are discussed. Cost modeling was done to prove the enormous gain in
revenue for the proposed fabrication scheme. It is proposed that the fabrication scheme of
templated diblock copolymer for making the master stamp for nanoimprint followed by
nanoimprint lithography for mass production has the largest potential for patterned media.
However, more R & D is needed for templated self-assembly of diblock copolymer
before it is ready for this application. E-beam lithography which is a mature technology
can also be a choice for making the stamp followed by mass production enabled by
nanoimprint lithography, without a significant loss of gain in revenue for ultra-highdensity media fabrications. Although the cost of a master stamp fabricated by E-beam is
estimated to be 50 times more than for templated self-assembly of diblock copolymer
lithography.
Thesis advisor: Caroline A. Ross
Title: Professor of Materials Science and Engineering
Acknowledgements
The successful completion of this thesis is due to the contribution and help from many
people. First of all, I would like to thank my thesis advisor Prof. Caroline A. Ross for her
consistent guidance and help. I still remember the discussion about my thesis with her
during her visit in Singapore for conference. She was always there when I had questions.
Thanks to her patience and clear guidance, my problems were always solved timely. She
also made me feel very comfortable in her group and I am proud that I have been a
member of Ross's group. Best wishes to all the group members!
Next, I would like to thank S.N. Piramamnayagam from Data Storage Institute,
Singapore. We had several discussions and he answered a lot of my queries. He also
provided me useful information about magnetic recording systems and shared with me
some of his perspectives on this project. Thank you very much for your sharing and help.
Also, I want to thank Prof. Eugene A. Fitzgerald for his guidance in course 3.207:
Technology Development and Evaluation, which provides a useful template of
technology evaluation for doing this project.
All the best to all the Master of Engineering students of 2008 class! Thank all of you for
being companions for one-year study and being my friends for life. Thank Manyin for
helpful discussion and suggestions about my project. And special thanks to my
groupmate - Anay, with whom I could share and discuss about the technical questions in
detail anytime.
Cliff, thank you. You are not only providing me important emotional support, but also
always being there for me on any problem I have. I feel so grateful to God for knowing
you. You will surely do great for your PHD research projects and also future careers!
I could not end without thanks to my parents, who are always supporting me, loving me
and never give up me. I can not express how lucky I feel to have such a blissful family.
Wish both of you healthy and let us meet soon.
Table of Contents
Abstract .....
....
......................
.... ...... ............................
............ ................ 2
Acknowledgement.......................................................................................3....
Table of Contents.....................................................
... 4
1. Introduction................................................................................
...... 6
PART I: TECHNOLOGIES............................................................................7
2. Description of Patterned Media Technology.......................................................7
2.1. Magnetic Recording - Materials and Recording Mechanisms......................7
2.2. Magnetic Properties vs. Magnet Size .................
............................... 10
2.3. Limitations of Conventional Media and Superparamagnetic Effect................
12
2.4. Patterned Media and Technical Barriers for Its Implementation......................14
3. Competing Technologies......
.....................
...........................................
16
3.1. Heat Assisted Magnetic Recording....................................................16
3.2. Flash/Solid State Drive...................................................
4. Fabrication Methods.....................................................
............
17
.................. 18
4.1. Lithography Patterned Media...........................................................18
4.1.1. Conventional lithography techniques
........................................
19
4.1.2. Templated self-assembly of diblock copolymer lithography ..............23
4.2. Self-Assembled Nanomagnets Patterned Media/Nanocrystal Superlattice...........28
5. Comparisons of Technologies and Possible Fabrication Schemes...........................
5.1. Technique 1) and 2)......................................................
29
..................... 30
5.2. Technical Barriers of 3) and 4) for Patterned Media Fabrication .............
30
PART II: COST, IP & BUSINESS MODEL.....................................................34
6. Cost Estimations and Comparisons for Fabrication Schemes..............................34
6.1. Comparison of Cost: Scheme B) vs. Scheme A)
- Templated Diblock Copolymer Self-Assembly vs. SEBL............................. 34
6.2. Comparison of Cost: Scheme B) vs. Scheme C)
- Diblock Copolymer vs. Magnetic Nanoparticles ......................................... 35
6.3. Proposed Fabrication Scheme: Scheme B) ..........
............................. 36
6.4. Cost Modeling for Scheme B) ............................................................. 38
7. Patents Relevant to Patterned Media and Fabrication Methods..........................39
8. Value Chain and Business Model.
42
..................................
8.1. Structure of HDD Value Chain and Our Value Proposition ....................... 42
8.2. Globalization of HDD Value Chain ...................
.....................................
43
8.3. Current HDD Market and Top Players ..............................................
44
8.4. Proposed Business Model and SWOT Analysis ......................................... 46
9. Conclusions............................................................................................ 49
References...................................................................................................51
Appendices ................................................................................................. 56
Appendix 1: Trends and future prediction of HDD industry...............
.................. 56
Appendix 2: Comparisons of SSD and HDD ......................................................... 57
Appendix 3: SEBL parameters .......................................................................... 59
Appendix 4: JBX-9300FS EBL system specification and charge...................................61
Appendix 5: Patent on patterning/lithography by self-assembly of block copolymers ...........62
Appendix 6: Patent on patterned media..............
..............................................
63
Appendix 7: Toshiba's pattern on patterned media and fabrication method of
forming islands in tracks/grooves .........................................................
64
Appendix 8: Seagate's patent on NCs superlattice technology for patterned media .............. 65
1. Introduction
The hard disk drive (HDD) industry has a history of more than fifty years and the future
is predicted to be bright by industry analysts such as Gartner, IDC and TrendFOCUS.
According to iSuppli', the annual revenue of HDD industry in 2007 was 32.8 billion
dollars, which increased 4.6% compared to 2006 and the shipped units passed half billion
in 2007 [2]. TrendFOCUS also predicted that the shipments would reach 750 million
drives in 2010 [3]. The HDD industry has achieved annual increases in areal density
approximately 60% in average since 1997, which exceeds Moore's Law for
semiconductor industry (refer to appendix 1).
Although HDD industry is a robust industry with high revenue, it is facing scaling
limitation problem together with the threat from flash/solid state memories. In order to
further scaling down and increase the storage density, we must overcome the limitation
imposed by the superparamagnetic effect, which occurs when the microscopic magnetic
grains of the disk are reduced to so small size that ambient temperature can reverse their
magnetic orientations, corrupt data and thus the storage device is unreliable and unusable.
One of the most promising methods to overcome this constraint is patterned magnetic
media technology [4]. Although there are many challenges in this technology, the large
potential gains in density offered by patterned media make it one of the potential new
milestones in the future of HDD industry. One common approach proposed by
researchers is using nanolithography to pattern the magnetic platter of the disk. Major
data storage companies such as Seagate, Hitachi and Toshiba, are devoting themselves
intensely into patterned media technology and launched projects on it.
However, real implementation of patterned media in HDD application is facing several
challenges. One of the most challenging tasks is the fabrication of discrete islands with
uniform size and shape, well ordered and well defined position on the disk. Most
importantly, the islands must have nanoscale dimensions less than 25nm to manifest
1iSuppli Corporation: a leading provider of procurement and supply chain management services for the
electronic components industry.
patterned media's higher areal density compared to conventional thin film media.
Today's state-of-art optical lithography can not do the job. E-beam lithography can
provide the required high resolution, while the cost and time needed are enormous.
Therefore, we need to come up with new fabrication methods to enable patterned media
mass production.
PART I: TECHNOLOGIES
2. Description of Patterned Media Technology
2.1. Magnetic Recording - Materials and Recording Mechanisms
The magnetic materials used in magnetic recording today are mainly ferromagnetic
CoCrPtX alloys (X = Ta or B) [5, 6]. Data is stored in the form of magnetic bit in
magnetic media, and reading and writing processes of the data are performed by
read/write heads (refer to fig. 2-2). The recording media technology is one key aspect for
the scaling evolution and the exponential growth of the hard disk drive capacity besides
the read/write head technology evolution. Upon external magnetic field (H), the magnetic
bits are magnetized and have magnetizations which either point to one direction or the
opposite direction which are parallel to their easy axes. This tendency to align the
magnetization along the easy axis is called anisotropy and anisotropy constant (Ku)
measures how difficult it is to change the magnetization orientation away from an easy
axis to another axis (Ku stands for uniaxial anisotropy constant assuming only one easy
axis). After removing the external field, remanent magnetization Mr left with the
magnetic bits represent the data which can be read by the head sensor. In order to write
the data, the applied external magnetic field by the write head should exceed the
coercivity of the magnetic material (He) for switching. Coercivity H, is the reverse field
that must be applied to a magnetized magnet to reduce its overall magnetization to zero,
which measures how permanent a magnet is (fig. 2-1) [5]. Coercivity is proportional to
anisotropy constant (HC - KU / M,) for magnetic materials, therefore higher anisotropy
implies larger coercivity [7].
M
GMR Read Inductive
Sensor
Write Element
H
I]
d
w_
J8~
N
RecordingJN
94B , Recording Medium
Fig. 2-1: Hysteresis loop of
permanent magnetic materials with
labels of remanence Mr, saturation
magnetization M, and coercivity H,
(Chikazumi and Charap, 1978).
S
NMedium
Fig. 2-2: A schematic drawing of
read/write elements for a longitudinal
recording medium. The read sensor is
of GMR type and the write head is of
ring type [1].
Generally speaking, the write mechanism has not changed
much through HDD history.
Larger field is used in modem magnetic recording as harder
magnetic materials are used
which has higher coercivity and requires higher write
field. The recent established
perpendicular recording uses a single pole type head which
produce twice larger write
field (fig. 2-3) (~ 4rnM) compared to that of longitudinal
recording (~ 2rMs) [7].
However the read head keeps revolutionizing when
magnetic bit size is scaled down
because the signal generated by the magnetic bit becomes
smaller (- Mrt for longitudinal
recording, where t is the thin film thickness) [8],
which requires read sensors with
comparable size and higher sensitivity.
Ring
I Type Head
Single Pole Type Head
\
,,
Recording Medium
Longitudinal recording
i
Soft Magnetic Underlayer
Bias Layer
Perpendicular recording
Fig. 2-3: Schematic drawings showing the difference
of write heads between longitudinal
recording and perpendicular recording [8].
Conventional media is fabricated using thin film technology in which one magnetic bit
consists of 50-100 magnetic grains and each one is one magnetic domain. The thin film
technology produces grains with different sizes and crystal orientations which have
different easy axes of magnetization [9]. Fig. 2-4 shows the magnetic grains of
conventional longitudinal recording thin film and the zigzag transition between two
magnetic bits [10]. Different crystalline orientation gives different preferred easy axis of
magnetization.
Fig. 2-4: TEM image of modem recording CoCrPtB media. The lightest grey areas are
the amorphous non-magnetic Cr rich boundaries which separate the magnetic Co rich
grains. The inset schematically shows a zigzag magnetic transition meandering between
the grains [1, 10].
The size distribution and orientations of the magnetic grains can be controlled by
improving and optimizing the thin film technology. However, uniform size, uniform inplane and out-of-plane orientations are not able to be achieved by thin film technologies.
Non-uniformities of crystal size, orientation and the zigzag magnetic transition between
bits generate noise when reading data. If there is not enough number of grains per bit, the
SNR (signal to noise ratio) is so low that hard disk drive does not give the desired
performance. An acceptable SNR requires the number of grains per one bit to be around
50-100. The SNR is related to N which is the number of grains per bit by equation [6, 8]:
SNR (dB) = 10 log (N)
(Eq. 2.1)
2.2. Magnetic Properties vs. Magnet Size
Magnetic properties such as coercivity, saturation magnetization, remanence and the
hysteresis loop are determined by the microstructure of the recording medium [11]. As
discussed above, the magnetic thin film microstructure largely affect the SNR of the
recording media. Consider a single magnet/one magnetic grain, the coercivity of the
magnet changes with the particle size following the schematic drawing shown below.
When the size is larger than do, it is muti-domain structure. When the size is reduced to
nanoscale which is less than do, the whole particle becomes single domain. The single
domain magnet can be single crystal or consists of several grains which are strongly
exchange coupled [8]. Particles with dimensions near 50Aex are expected to be single
domain, where Aex is the exchange length near which the particle is coherently
magnetized [4]:
x
M=
2A
(Eq. 2.2)
This single domain to muti-domain transition is due to the minimization the total energy
which is related to the wall energy and magnetostatic energy. The wall energy is
determined together by exchange energy and anisotropy energy [12-14]. The switching
mechanism changes to domain wall motion for multi-domain structure. For single domain
structure, the switching mechanism is coherent (spin rotation) for smaller particle size,
but becomes incoherent (such as buckling, curling) [12-14]. When the single domain
particle size is further reduced, the magnetic nanograins become superparamagnetic
which will be further explained in the next section [13]. The working region of magnetic
recording media is the shaded single domain, thermal stable region with particle/grain
size between d, and do. In this range, the non-interacting single domain particles behave
magnetically according to the series of hysteresis loop at different aligning angles 0
between easy axis and applied magnetic field shown in fig. 2-6, assuming coherent
rotation (Stoner & Wohlfarth, 1948).
0
6.
30
0
U
ds
do
No
Particle diameter d
Fig. 2-5 [12]: Coercivity He vs. grain size d.
sIx
-1
0
1
h
Fig. 2-6: Series of hysteresis loop of a single domain particle with various aligned angles
0 with respect to the easy axis direction (Stoner & Wohlfarth, 1948).
2.3. Limitations of Conventional Media and Superparamagnetic Effect
The magnetic grain size is scaled down by tuning thin film processing parameters,
consequently, size of one magnetic bit which consists of a certain number of magnetic
grains is shrunk and thus more data can be stored per unit area. When the grain size is
scaling down to a limit, the media is subject to superparamagnetic effect where the
energy barrier required to change the direction of the magnetic moment of a particle is
comparable to the ambient thermal energy. It is a small length-scale phenomenon by
which magnetic materials exhibit a behavior similar to paramagnetism below the Curie or
the N6el temperature. At this crossover point, the rate at which the particles randomly
reverse magnitization direction becomes significant and thus the magnetic particles
behave paramagnetically even at ambient temperature. The bit thus becomes unstable and
data is lost. To calculate the smallest magnetic grain size that can be used for information
storage, let us consider the rate of magnetization switching expressed by Arrhenius Neel
law:
1
r = -exp(-E,
I kBT),
(Eq. 2.3)
where EB is the energy barrier with the existence of an external field of H, fo is a constant
representing the attempt frequency on the order of 109-1012 Hz, k, is the Boltzmann
constant, and T is the temperature.
EB can be expressed as [1]:
H
E8 (H,V) = K V(1l--) M ,
(Eq. 2.4)
where Ku (magnetic property of material) stands for uniaxial anisotropy constant, V is the
volume of the magnetic grain, The exponent n is 1.5 in isotropic longitudinal media, and
Ho is the intrinsic switching field which is related to the required write field H, by [8]:
Ho a H, s Hý ;
K,
M,
(Eq. 2.5)
where Ms is the saturation magnetization, H, is the coercivity and Hw is the write field.
For data storage stable under zero external field for over 10 years (industry standard) at
ambient temperature, the criteria is calculated to be EB = KV > 40k,T . That means
thermal stability imposes a minimum bit size which can be reduced to. The minimum
grain and thus bit size vary for different magnetic materials with different anisotropy
constants. This theoretical estimation is based on assumptions of isolated particles and
coherence switching mechanism [4]. However, the interactions among the magnetic
grains in the conventional recording film must be considered as they are closed to each
other separated by a distance of grain boundaries only. The energy barrier can be lower
by exchange coupling between magnetic particles in thin film [6]. Also, as mentioned
earlier, the media noise depends strongly on the microstructure of the film including the
grain size distribution, grain orientation and also grain boundaries [6]. This implies better
thermal stability of patterned media compared to conventional media with same bit size
and thus less stringent on bit size limited by thermal stability criterion. In addition,
incoherent switch mechanism gives an energy barrier lower than coherent switching as
well. If the 10 years thermal stability criterion of KUV/kBT 2 60 for thin film media is
used, assuming K, = 2.5 x 106 erg/cc 2 [15] for Co-alloy [6], the minimum grain size is
calculated to be 9.7 nm. Range of magnetic grain size in modem magnetic recording is
around 5-15 nm [7] which is already approaching the superparamagnetic limit of current
magnetic recording materials Co-alloys.
People have considered to reduce the superparamagnetic limit size by using high
anisotropy materials such as FePt or CoPt, but their large coercivity
(K =6x106 -10x10 6 erg/cc for bulk Llo FePt [16]) far exceed the writing field
capacities of modern write poles with saturation magnetization density approaching the
highest recorded value (~26 kGauss3 [15]) [7] and that is how heat assisted magnetic
recording comes up (problems of this approach will be addressed later in the competing
technologies section).
2 erg/cc:
CGS unit which stands for energy per cubic centimeter,
1 erg = 107 J.
3 Gauss: CGS unit for magnetic flux density, 1 G = 10" T
2.4. Patterned Media and Technical Barriers for Its Implementation
To summarize, the triangular conflictions among thermal stability, SNR and writability
restrict the areal density of conventional thin film magnetic media from further increasing.
Patterned media can solve the problem by making well ordered, uniform size, discrete
In
magnetic islands which'are single magnetic particles, with each island storing one bit.
this way, we can reduce the bit size using writable magnetic materials with moderate
anisotropy constant, providing good thermal stability and acceptable SNR [1].
The schematic drawing in fig. 2-7 shows the nanoarrays we need to fabricate for
2
patterned media. In order to achieve aimed areal density of 1Tb/in , the nanodot
dimension is around 12.5 nm which challenges the current nanoprocessing techniques
[17]. Table 2-1 gives the island sizes and periodicities with regards to various bit areal
density requirements.
Tyia
' \
Mannati/Nonmagnetic
eidcte
isadszsad
island size
(nm)
Periodicity
(nrm)
300
30
45
500
1000
25
18
35
25
1500
14
20
Bit areal
density
(Gblin2)
Areal density = 1Tb/sq in
Fig. 2-7: A schematic drawing showing
Table 2-1: Theoretical island sizes and
nanoarrays of patterned media and
periodicities in patterned media with
theoretical dimensions for 1Tb/inch 2 areal
regards to various areal density
density (Courtesy: S.N. Piramanayagam).
requirements (Hitachi).
For patterned media to be finally implemented in real production, the most challenging
task is the media fabrication. Although the concept of discrete islands disk seems
straightforward, there are many stringent requirements on the fabricated media. The first
requirement of patterned media is to make nanoscale bit islands with dimensions less
than 25 nm to achieve superior density compared to the recent implemented
perpendicular magnetic recording (PMR). An areal density of 345 Gb/inch 2 has been
demonstrated on PMR by Hitachi researchers in 2006. The highest areal density HDDs
using PMR technology which is about 240 Gb/inch2 were shipped July, 2008 by Seagate.
It is estimated that to achieve higher areal density compared to the current perpendicular
magnetic recording, the periodicity of the patterned nanoarrays should be less than 50
nm, which means that the island dimension should be less than 25 nm. At this dimension
range, the magnetic particle is expected to be single domain [4]. The second requirement
is the aspect ratio of the magnetic island can not be too high, in order to ensure coherent
magnetization reversal. Coherent magnetization reversal is favored for high writing
speed, because it has shorter sub-nanosecond switching time compared to incoherent
switching which is around 1-2 ns. Besides nanoscale dimension, moderate aspect ratio,
the nanoislands must have uniform size and shape and well ordered into nanoarrays with
enough separation distance, which keeps the switching field distribution narrow and
ensure good performance of the media. Last but not least, the bit sizes have to be
controlled above superparamagnetic limit of the selected magnetic materials for thermally
stable performance [4].
Besides the fabrication challenge with the highest technical barrier, other essential
elements for patterned media commercialization include: 1) read sensor revolution which
can read nanoscale bit, 2) flyabiltiy which allow the head to fly under 7-10 nm, 3) signal
processing/synchronization. Technical barrier and these technologies are expected to be
much lower compared to fabrication challenge although signal processing, in particular,
synchronization is still at the research stage [1]. Read/write head is always under
intensive research to accommodate higher storage density. Hitachi has announced the
successful development of current perpendicular-to-plane giantmagneto-resistive (CCPGMR) heads recently (Oct, 2007), which is expected to be implemented in shipping
product in 2009 [18]. CCP-GMR is the smallest read-head technology currently (30-50
nm) developed for ultra-high-density storage media, and may be used in the patterned
media HDD system [18]. Discrete track PMR media, which has recording tracks
separated by grooves is under vigorous research, can serve as an intermediate technology
towards discrete bits media (patterned media). It has been shown experimentally that
lower
discrete track recording (DTR) media give noticeably better SNR and significantly
adjacent track erasure compared with continuous media at the same track width, which
are important when increasing areal density [19]. Flyability issue was also largely solved
in developing discrete track media [17]. Therefore, whether and when patterned media
can be realized mostly depend on the fabrication methods development and innovation,
which will be addressed later after the discussion of competing technologies.
3. Competing Technologies of Patterned Media
3.1. Heat Assisted Magnetic Recording
The most possible internal competing technology of patterned media is heat assisted
magnetic recording (HAMR). Basically, this technique uses a laser to locally heat the
magnetic material during writing process to lower down the coercivity of the materials
below the available write field [20]. Therefore, as discussed, materials with a higher
anisotropy can be used so that the grain size limited by the superparamagnetic effect can
be further reduced and thus areal density is increased. Seagate CTO Mark H. Kryder
predicted that with this technique, a thermally stable grain size smaller than 3 nm can be
achieved by using high anisotropy media such as Llo FePt, which gives areal densities
well beyond 1 Tb/in 2 theoretically [21].
Fig. 3-1: Principle of HAMR [20].
Although the principle and fabrication of HAMR seems easy, it's not yet commercialized
yet as it is facing a lot of technical challenge. The major problem comes from the high
working temperature and thermally induced mechanical failure. Both the air pressure
change at the laser spotted area and the nano-deformation of the slider body will lead to
noticeable change of slider's flying performance. Repeated heating and cooling process
can also lead the head-disk interface to intense thermal strain/stress fields. Furthermore,
the stress field can change the magnetization behavior of the grains thereby affecting the
magnetic performance such as the permeability in the head [22, 23]. Also, integration of
optical elements (laser) with magnetic elements in one head is challenging. The optical
spot size has to be small enough to give the localization of medium heating which should
be no larger than the order of the recorded bit size [24]. Last but not least, since high Ku
materials have a chemically ordered structure that requires elevated substrate deposition
temperature, fabricating reduced grain sizes is much more of a challenge compared to
current Co-alloys [20].
As we can see, there still remain many challenges for HAMR to be realized. It is difficult
to predict whether HAMR or patterned media will come out first. Although there is
possibility that HAMR comes before patterned media, it will not affect the development
of patterned media which could be built upon HAMR technology and further extend the
areal density. Therefore, Rather than saying HAMR is a competing technology of
patterned media, it is more like a stepping stone that will give the disk drive industry
breathing room to explore and develop ultimate ultra-high-density recording technology
such as patterned media.
3.2. Flash/Solid State Drive
Solid-state nonvolatile memory market has grown at an incredible rate since first
introduced around fifty years ago. Floating gate (FG) device is the dominate design in
this industry from the beginning till today. The floating gate flash cell is structurally
different from a standard MOSFET in its floating gate, which is a polysilicon layer
electrically isolated by dielectrics The most widespread memory array organization is the
so-called flash memory, which got its name because it could not be erased by bytes but
could only be erased by the entire chip or large sections of the chip [25]. The first
commercial flash product was invented in Toshiba in 1984 [26]. It has been quickly
expanding its market because of much lower cost than byte-programmable EEPROM
(Electrically Erasable Programmable Read-Only Memory) and therefore has become the
dominant technology in non-volatile, solid-state storage industry. Although a huge
commercial success, the floating gate flash is approaching its limit for continuous scaling
of the device structure beyond the 65 nm node. This scaling limitation stems from the
extreme requirements put on the FG isolation layers, in particular the tunnel oxide
isolating the FG layer from the crystalline silicon substrate. Tunnel-oxide thickness with
values in the range of 9-11 nm can be hardly further reduced in recent flash memory
developing, implying a scaling rate that is not comparable with that of transistors [27]. A
novel technology - embedded nanocrystals (NCs) flash technology, coming as a solution
for flash device scaling problem, is under intensive research [28, 29] and is expected to
be commercialized in 2009. This technology provides the flash devices better endurance
characteristics, longer retention time and fast read/write [30].
However, further scaling down of flash cells still faces challenges which keeps their areal
density lagging behind HDD, and their price per bit is not comparable to HDD (refer to
appendix 2 for comparisons). Although solid state drive/flash is attractive when
considering speed, noise, power consumption, and reliability (refer to appendix 2), it is
expect that as long as hard disk drives can continue the areal density growth rate, they
will enable capabilities and features that are not possible at an attractive price with SSD.
4. Fabrication Methods for Patterned Media
4.1. Lithography Patterned Media
When fabricating uniform nanoarrays with well-defined position and size, lithography
patterning is the first nanoprocessing technology that researchers think about. The
discrete island of patterned media should be patterned based upon the perpendicular
recording media [1]. The material used today for the magnetic film in current magnetic
recording technology is CoCrPt polycrystalline alloy with some addition components
such as B or Ta. During the annealing process, the added elements improve the
compositional segregation into magnetic grains which is high in Co and surrounding
nonmagnetic region which is low in Co [6]. The magnetic grains has their easy axes
perpendicular to the disk plane in perpendicular recording media, while are parallel to the
disk plane in longitudinal recording media. PMR is preferred as a base point for the
fabrication of patterned media because it provides better writability (write field = 4irM,,
[7] twice larger than longitudinal recording), better orientation uniformity, extended
higher areal density and was well established recently.
4.1.1. Conventional lithographytechniques
Refer to table 4-1 for a summary of the conventional lithography techniques. These
techniques are said to be conventional because they are all top-down approaches for
fabricating nanostructures. Some of them are high resolution techniques which were
developed and commercialized in recent years such as E-beam lithography and
nanoimprint lithography.
From the discussion of the patterned media requirements, well ordered nanoarrays with
periodicity less than 50 nm need to be fabricated for patterned media, which implies a
minimum resolution of 25 nm. By examining the resolution limit of each listed
lithography method, it can be found that only EUV, X-ray, E-beam lithography, focused
ion beam lithography and nanoimprint lithography can satisfy the resolution requirement.
However, EUV lithography and X-ray lithography are extremely expensive because of
the requirement of complex optical system, stringent requirements of the masks. For an
areal density of ITb/in 2, even higher resolution (-12 nm) is needed which challenges the
state-of-art high resolution lithography techniques. Focused ion beam lithography is more
expensive compared to E-beam. Therefore, only E-beam lithography and nanoimprint
lithography will be discussed here.
I
Fabriction mthodsResoluion ()
IB
Limiation
I
Conventional optical lithography
R = kLNA
Low resolution,
state-of-art: R - 60 nm
Extreme ultraviolet lithography
X- 10-14 nm,
R - 30 nm
Strongly absorbed by almost all the
materials, special mask needed
X-ray lithography
?,- 0.2-10 nm,
R - 20 nm
Besides the same problems above,
high intensity x-ray source needed
Interference lithography
R = /?2sinO
Difficult to obtain circular pattern
Electron beam lithography
R -- 10 nm
Low throughput, high cost,
4
Focused ion beam lithography
R - 10 nm
Low throughput, high cost
Nanoimprintlithography
R ~ 5 nm demonstrated
....
..
(Fig. 4-3) [31]
~-----
proximity effect
Resolution relies on stamp
fabricated by other methods such
as E-beam, high cost of stamp,
stamp wear and lifetime
Table 4-1: A summary of conventional lithography methods with
comparisons of
resolution limits and other limitation [32, 33].
Let us look into scanning electron beam lithography (SEBL) first. SEBL
can write
patterns of almost all arbitrary shape with high resolution (-10 nm)
by scanning the
electron beam through the resist surface with no need of mask. The
patterns are divided
into pixels and defined using computer-aided design (CAD). The
pixel size is determined
by the size of the electron beam, and it takes longer time to write
larger pattern areas with
more pixels. A beam blanker is used for stop the electron beam
from reaching the resist
area without pattern. Large area of pattern is divided into
many fields within which the
electron beam is defected to the exposure pixel and stage movements
are not needed (fig.
4-1) [33]. Refer to table I in appendix 3 for various actual
field dimensions corresponding
to different combinations of pixel size and digital field size.
4 Proximity
effect in E-beam lithography: during an e-beam exposure
of the resist, the interaction region
with electrons is larger than the size of the incident probe
due to elastic and inelastic scattering of the
electrons in the resist and substrate materials. Distortion
or blurring of the transferred pattern happens from
this effect.
A field
Fig. 4-1: A schematic drawing showing the concept of pixel and field.
The total scanning time is limited by: (1) resist sensitivity; (2) beam current; (3) data rate
limits on the tool; (4) stage motion; and (5) shot noise limitations on resolution [34].
Refer to table II in appendix 3 for exposure time/pixel transfer rate with respect to resist
sensitivity and current density, and typical data rates for different SEBL types are shown
in table III.
The beam spot size can be calculated using expression:
d = (4i/K2B)/2 a,
where numerical aperture/half angle a
(Eq. 2.6)
10-3 ,i is the beam current related to brightness
(B), which varies for different electron sources. The beam current density is related to the
source brightness by:
J = rcBa 2
(Eq. 2.7)
The exposure time per pixel or the dwell time per pixel is:
t, = S /J,
(Eq. 2.8)
where S is the resist sensitivity in C/cm 2 (or e-/nm 2 /pisec).
The second high resolution lithography technique to be discussed here is nanoimprint
(refer to fig. 4-3 for 5 nm feature size demonstrated). There are mainly two groups of
nanoimprint lithography (fig. 4-2): a) thermal nanoimprint. In a standard T-NIL process,
a thin layer of imprint resist is spin coated onto the sample substrate. Then the mold,
which has predefined topological patterns, is pressed into the resist under certain pressure
and at elevated temperature which is above the glass transition temperature of the resist
polymer. After being cooled down, the mold is separated from the sample and leave resist
pattern on the substrate. Finally, a pattern transfer process such as reactive ion etching
transfer the pattern in the resist to the underneath substrate. b) UV nanoimprint/step-andflash lithography. In UV-NIL, Photo curable (UV sensitive) low viscosity resist is applied
to the sample substrate. Then the mold made of transparent material such as fused silica
is brought into contact with the resist, which is cured in UV light meanwhile and
solidifies. After mold separation, a similar pattern transfer process is used to transfer the
pattern in resist onto the underneath substrate [35].
a)
b)
j
.9
Fig. 4-2: a) thermal nanoimprint; and b) step-and-flash nanoimprint processes [36].
(a)SiO, NIL Mold
(b) NIL Poilymer imprint
(b)
NILPolymerImrn
h.- Ai R nm (nntnrtr.
'"
Fig. 4-3: The 5 nm feature fabricated using UV-NIL.
4.1.2. Templated self-assembly of diblock copolymer lithography
After the invention of nanoimprint lithography by Stephen Chou in 1995 [37], people
proposed to use this cheap and high resolution technique to enable the mass production of
patterned media [4, 17, 35, 36, 38]. However, a master stamp/mold with large area of
nanoarrays still needs to be fabricated using other high resolution lithography method
such as E-beam lithography. The time and price of making such a stamp using E-beam is
enormous and not practical, which scares HDD manufacturers to pursue it (cost
estimation will be provided later). A cheaper way to fabricate the stamps is using
templated self-assembly of diblock copolymers.
Self-assembly of diblock copolymer has been demonstrated as a promising template for
nanoscale lithography since 90th. Diblock copolymers A-B consist of two chemically
different polymer chains or blocks A and B joint together. Because of connectivity
constraints and the incompatibility between the two blocks, if A and B do not mix, the
copolymer film spontaneously self-assemble into ordered point-like or linear patterns
over a large area of alternating chemical composition at equilibrium [39]. General
processing steps are firstly depositing a thin polymer spin-coating of films using polymer
solutions in toluene onto the desired substrate and the film thickness is controlled by
varying spinning speed and polymer concentration. The films were annealed around
range 100 0 C-2000 C which is a temperature above glass transition temperatures of the
polymers, for significant long time to obtain well-ordered morphologies. Upon annealing,
block copolymers self-assemble into nanometer scale domains to minimize the free
energy of the whole system [40, 41]. Either block could then be selectively removed due
to their chemical or physical properties dissimilarities, leaving nanostructures of the other
block which can be used as mask for lithography. The microdomain patterns are
transferred directly to the underlying substrate [42].
The morphology of the phase largely depends on the volume fraction of the blocks at a
given XN [43]. Spherical morphology is patterned media applications. The domain period
depends on the segment length of the polymer, the overall number of segments, and the
Florey-Huggins interaction parameter for a certain block copolymer [39]:
<< 1, disordered,
unperturbed chains
Nj - 10, weak segregation, fluctuations aN"/ 2
2/3 1/ 6
>> 10, strong segregation, D ~aN
where
'
(Eq. 2.9)
is the Florey-Huggins interaction parameter, N is the overall number of
segments/monomers, and a is the segment length. From this theory, in order to get
islands-sea microstructure with minimized nanoscale domain size for patterned media, it
is not only necessary to control the volume fraction of each block, but also very important
to choose the diblock copolymer with high X. In addition, the polymers should have good
etching selectivity between the two blocks to make lithography process feasible. It is
possible in theory for diblock copolymers to self-assemble into ordered periodic
structures at the molecular scale (5 to 50 nm) [44], however, the smallest domain size
demonstrated in experiment is 18 nm which has not met the requirement for 1Tb/in2 areal
density.
Dense periodic nano-arrays of holes and dots with feature size down to 20 nm have been
fabricated on a silicon nitride coated silicon wafer using asymmetric polystyrenepolybutadiene (PS-PB) and PS-polyisoprene (PI) diblock copolymers [42] (see fig. 4-4).
Fig. 4-4: a) SEM micrograph of a partially etched, ozonated monolayer film of spherical
microdomains. PI domains were exposed as holes which appear darker after the
continuous PS matrix at top was taken off; b) SEM micrograph of hexagonally ordered
arrays of holes in silicon nitride on a thick silicon wafer. The pattern was transferred from
a copolymer film such as that in a).
However, diblock copolymer as a self assembly system suffers common problems of selfassembly such as defects and lack of long-range order. Topographically [45]/chemically
[46] patterned substrate can be used to template/guide the self-assembly of diblock
copolymer for fabrication of defect-free nanostructures with long-range order. Paul
Nealey's group from Wisconsin Research proposed chemically patterned imaging layer
on the substrate formed by interference patterns of two or more extreme ultraviolet EUV
beams. The patterned surface manipulates the wetting behavior of diblock copolymer
films and guides the spatial microphase separation of PS-polymethylmethacrylate
(PMMA) in their experiment, which transfers the imaging layer pattern to polymer film
[46, 47]. However, the feature and domain size formed by this technique depends on the
imaging layer patterned by other lithography method. It seems not really manifesting the
good features of diblock copolymer self-assembly lithography such as high resolution
and low cost. Another approach is to use topographical templates such as trenches or
shallow grooves. J. Y. Cheng and C.A. Ross et al from MIT have experimentally and
theoretically (free energy minimization) designed topographical templates (grooves)
which can lead to precisely modulated diblock-copolymer nanostructures with
controllable spatial arrangement of sphere arrays [48, 49]. By combining top-down and
bottom-up nanofabrication, templated self-assembly of PS-polyferrocenyldimethylsilane
(PFS) block copolymer gave perfect, close-packed arrays of PFS spheres with long range
order in PS matrix. Very few defects were observed up to 12 rows with a long range
order of at least 2 0acros long (acro,,,,, is the centre-to-centre spacing shown in fig. 4-5 a,
right, which is 28.6 nm for this polymer). A preferential wetting brush layer of PFS
molecules (see fig. 4-5 a, left) were found both at the bottom and sidewall of the silica
grooves, which has a thickness t ~10 nm. It was assumed that the preferential wetting
layer on the vertical sidewalls of the groove drives the domain ordering [50].
The key in this technique is to ensure the width of the groove to be commensurate with
the ideal periods for desired number of sphere rows, which were determined in their
experiment (see fig. 4-5 b and c) [49]. When the groove width is incommensurate with
the ideal period, the resulting block copolymer domains have defects and are compressed
or expanded to fit the groove. Near-perfect arrays of N rows of islands formed for a
confinement width W where (N - 0.5)d < W < (N + 0.5)d. Confinement width is the
actual groove width minus the thickness of two brush layers on the wall, and d is the
equilibrium row width and is 24.8 nm for this polymer (see fig. 4-5 a, right) [49, 50]. For
example, in order to fit N = 9 rows of stable spherical domains, the confinement width is
8.5-9.5d. And the actual groove width can be calculated to be Dgroove = Wd + 2t = 230.8255.6 nm.
I::
a)
::::I
·
:
000
94Ode
*d* °
° °
0 0
b)
13
i
12-
C)
11-
-
10
1
12
is
Confinement width (d)
Fig. 4-5: a) schematic drawings of spherical PFS domains in PS matrix and equlibruim
row width d; b) Plan-view scanning electron micrograph of ordered arrays of PFS
domains with N = 2 to 12 rows; c) The number of rows in the groove, N, plotted against
confinement width, W, showing the widths at which arrays with N rows are stable. The
confinement width is expressed in terms of d, the equilibrium row spacing, which is 24.8
nm in this polymer.
Similar studies were also done by K. Naito et al. in Toshiba research team using PSPMMA. A paper reporting their demonstration of a 2.5 inch disk with patterned
nanoarrays (fig. 4-6) was published [38]. However, the island size formed is around 40
nm which is too large for patterned media application. Also, their study did not show a
precise control of the groove width over number of nanoarrays rows. It seems that they
have little control over the domain size and groove width for precisely modulated diblock
copolymer nanostructures. Nevertheless, it is the first patterned media prototype
fabricated by topographically templated self-assembly of diblock copolymer, which
shows the feasibility of this technology for patterned media application. Patents were
granted on their work [51-53].
Co74Cr6Pt, dot
Fig. 4-6: Demonstration of 2.5 inch disk with patterned nanoarrays by K. Naito et al.
4.2. Self-Assembled Nanomagnets Patterned Media/Nanocrystal Superlattice
Nanocrystal (NC) superlattices have attracted increasing attention since they were first
reported in 1989 [54]. The general approach is to firstly chemically synthesize the
nanoparticles, and then spread the colloids on the substrate and let the carrier solvent to
evaporate slowly followed by annealing [55].
Self-assembled FePt nanocrystal
superlattice was reported by IBM Research Centers and Seagate Research together in
2000 [55]. Synthesis of monodisperse iron-platinum (FePt) nanoparticles by reduction of
platinum acetylacetonate and decomposition of iron pentacarbonyl in the presence of
oleic acid and oleyl amine stabilizers produces particle sizes available from 3 to 10 nm
(diameter). The synthesized particles also have narrow size distribution with a standard
deviation of less than 5%. However, these nanoparticles are not suitable for patterned
media as they are paramagnetic. Thermal annealing converts the internal particle
structure from a chemically disordered FCC phase to the chemically ordered facecentered tetragonal phase, which transforms the nanoparticle superlattices into
ferromagnetic assemblies. However, annealing process reduces the inter-particle spacings
from -4 nm to -2 nm which is too close for patterned media application (refer to fig. 4-7
below for the superlattice structure). It was claimed that the separation distance may be
increased by capping ligands on the nanoparticles [55]. Later experimental and
theoretical study shows that low temperature (<550 0 C) annealed FePt assembly can
contain a significant fraction of superparamagnetic particles, while higher temperature
annealing (>600 0 C) lead to significant aggregation of the FePt nanoparticles with the
presence of undesirable ferromagnetic coupling between particles [56]. The results imply
that it is very difficult to control the annealing temperature for forming desired Llo0 phase
of FePt without significant nanoparticle aggregation. Although this is not yet a mature
technology for fabricating patterned media, Seagate was granted a patent on selfassembly of nanoparticles such as FePt in locking patterns defined by conventional
lithography method, which has similar concept as templated self-assembly of diblock
copolymer discussed above [57] (see appendix 8). After this study, some researchers
coated the FePt particles with coatings like SiO2 (or Fe 3 0 4 [58]) to improve the chemical
ordering of FePt nanoparticles, and achieved FePt NCs superlattices with coercivity as
large as 18.5 kOe 5 [15] in spite small size of 6.5 nm [59]. This implies that it can be used
to increase the areal density; however, this is still conventional media technology, which
is not economic as the increasing in areal density may not be able to compensate the cost.
Fig. 4-7: TEM micrograph of a 3D assembly of 6 nm FePt
sample made by Shouheng Sun et al.
Another significant work is the self-assembled cobalt nanocrystal supperlattices over
a
lithographically patterned area (-100 nm by 100 nm) demonstrated by C. T. Black and
Shouheng Sun et al [60]. They also obtained a patent on magnetic storage medium
formed of self-assembled magnetic particles [61].
5. Comparisons of Technologies and Possible Fabrication Schemes
First of all, let us recall back previously discussed nanoprocessing techniques which
are
potential for patterned media fabrication: 1) scanning electron beam lithography
(SEBL);
5 Oe: CGS unit for magnetic field strength, 1 Oe = 103/47 (A/m).
2) nanoimprint lithography (NIL); 3) topographically templated self-assembly of diblock
copolymer; 4) self-assembly of magnetic nanocrystals.
5.1. Technique 1) and 2)
Among these techniques, the first two (SEBL and NIL) are top-down methods which are
mature and commercialized technologies, with companies providing lithography
facilities, materials, masks and services. The nanoimprint lithography business emerged
in the late 1990s, started with Nanonex and Obducat. EV Group, Molecular Imprints and
Suss also announced tools subsequently. Molecular have recently released one new
system to Hitachi - "IMPRIO HD 2200" especially for development of patterned media.
Toshiba also says it has shipped a few systems from it, mostly in Japan [62, 63]. Today's
leading-edge 193 nm immersion optical scanners (- 60 nm feature size) sell for as high as
$40 M. In contrast, a state-of-the-art nanoimprint tool may sell for up to $10 M, and most
nanoimprint tools sell for as cheap as $100,000 [62, 63]. By comparison, the price of
SEBL facilities is generally above $4 M [64]. However, nanoimprint needs master stamp
generated by other high resolution lithography method, which can be quite expensive too.
5.2. Technical Barriers of 3) and 4) for Patterned Media Fabrication
The latter two techniques involving self-assembly (bottom-up) are still in research stage.
And in order to achieve long-range order for patterned media application, self-assembly
is usually combined with top-down methods, which provides topographical template for
self-assembly processes. The structures made by technique 3) showed in the experiment
give defect-free long-range order area of around 300 nm by 400 nm [49]. However, for
patterned media, we need to make defect-free nanostructures of even longer-range order
(- cm). Cheap and convenient characterization methods are needed for examination of
defects; signal processing techniques need to be developed for error detection and
correction to accommodate for the defects if there are. Technique 4) which is selfassembly of magnetic particles not only has the same problems as 3), but also, FePt
nanoparticles with very small dimension (3-10 nm) are not ferromagnetic without
annealing while the NCs tends to aggregate after annealing. Also, the separation distance
between NCs is too small for patterned media. Therefore, both 3) and 4) technologies
have problems and are not ready for patterned media. However, the last one which
evolves more complex chemistry has relatively high technical barrier currently, thus more
studies need to be done to further prove its feasibility as a fabrication method for
patterned media. In contrast, the diblock copolymer self-assembly system has been
proved in a patterned media prototype [38]. It is also more flexible which can adjust to a
range of groove width commensurably, compared to magnetic hard particles (colloid)
self-assembly in which defect-free ordering only occurs for certain widths [49].
In the case of guided self-assembly of diblock copolymer, we do not need to write the bit
one by one, islands will form by self-assembly. However, circular grooves are needed to
facilitate the ordering, otherwise, the self-assembled nanoarrays lack long range order (a
necessary requirement of patterned media). As templates such as grooves are needed to
guide the self-assembly process, the area available to pattern the nanoarrays is reduced
and therefore smaller bit dimension is needed to achieve the desired areal density
compared to whole surface patterning. According to studies mentioned by K. Naito et al,
their groove widths varies from 60 nm to 250 nm, and the land spacing between grooves
was kept as 400 nm [38]. A schematic drawing below (not to scale) shows the grooves
needed to guide self-assembly of diblock copolymer within them. The Ni master disk
stamp with these circular groove patterns were purchased from Nikon Corporation (price
unknown) [38] and in the experiment of Ross et al, they used E-beam to draw the groove
patterns [49].
Groove width:
60-250 nm
Spacing:
400 nm
Fig. 5-1: A schematic drawing which shows the grooves and spacing dimensions formed
by the Ni master stamp in the experiment by K. Naito et al.
The data density is thus only a fraction of the potential density with nanoarrays on the
whole surface. This fraction can be estimated as f =
the width of the grooves and
Dspacing
groove
, where Dgroove is
Dgroove +Dspacing
is the width of inter-groove spacings. Let us use the
experiment results of Ross et al. as an illustration to calculate the areal density generated
by this technique. W rows of polymer nanoarrays are formed in the groove with row
spacing of d and inter-particle spacing of across. The areal density in the patterned area can
be calculated as:
x 101 x 2.542 (bits / in 2 )
across X
Ogroove
The whole disk areal density can be estimated by:
Areal density of patterned area x f ( f =
groove
Dgroove +
W
x
2d x (Wd + 2t)
2=
W
+2
(Wdx+2)
Wd +2t +Dspcing
spacing
1014 x 2.54 2 (bits/in2)
x 1014 x 2.542 (bits /inch 2 )
D-)
2
2 dWd+ t+Dspacing
*
*
o
a,- =
111 1
d --
o =24.8 nMI
2 "?
Fig. 5-2 [49]: Schematic drawing showing the row spacing d and particle spacing across.
Where d is the equilibrium row spacing, W is the number of rows, t is the thickness of
polymer brush layer. Substitute the actual experimental values of d = 24.8 nm, W=12
(maximum), t = 10 nm [49] into the formula, and let Dspacing =100 nm, we get total areal
density of648Gb/in2 . Therefore for this technology to be applied for patterned media
fabrication to achieve 1Tb/in 2 areal density, more research is needed to further reduce the
periodicity or domain size of the diblock copolymer self-assembly systems. The size of
the spherical nanodomains depends largely on the length of the blocks and the FloreyHuggins interaction parameterX as discussed in earlier section. More R& D work needed
to achieve smaller domain size and longer-range order (- cm) in which we could
contribute and generate value.
5.3. Possible Patterned Media Fabrication Schemes
Technically speaking, possible fabrication schemes of patterned media are: A)
SEBL+NIL; B) topographically templated self-assembly of diblock copolymer + NIL; C)
self-assembly of magnetic nanocrystals. A schematic drawing below shows the current
technological barriers for the three fabrication scheme with respect to technology
evolution timeline. Scheme A) has the lowest technological barrier because both SEBL
and NIL are relatively mature and commercialized technologies. The only problem is that
the resolution of current SEBL can only reach 10 nm generally, and proximity effects
also affect the quality of dense features like which in patterned media. Scheme C) has the
highest technological barrier while scheme B) has medium barrier compared with the
other two. The reasons were stated above when discussing the technological barriers of
templated diblock copolymer self-assembly and NCs superlattice respectively.
Technological
Barriers
Fig. 5-3: Comparisons of the technological barriers among fabrication schemes A), B)
and C).
PART II: COST, IP & BUSINESS MODEL
6. Cost Estimations and Comparisons for Fabrication Schemes
6.1. Comparison of Cost: Scheme B) vs. Scheme A)
- Templated Diblock Copolymer Self-Assembly vs. SEBL
Using self-assembly of diblock copolymer guided by circular groove to fabricate the
stamp is a relatively cheaper method compared with E-beam lithography. After the stamp
is made, the following cost in the next step is not significant compared to the stamp cost
because mass production is enabled by using nanoimprint lithography. Also, you can use
the father stamp to make many daughter stamps using nanoimprinting.
Below is an approximated calculation to show how much usage of E-beam lithography
equipment costs to write a 2.5 inch disk area with island dimension of 10 nm which gives
an areal density of 1.5 Tb/ inch2 .
Let us consider the data rate and the stage moving/settling time as the limiting factors for
total scanning time. By approximating the stage moving/settling time to be 4 sec from
field to field [34] and assuming 10 nm pixel size (one pixel for one magnetic island), the
total writing time for JBX-9300FS EBL System (microelectronic research center,
Georgia Tech) (50 MHz)to pattern a whole 2.5 inch (6.35 cm) disk surface with 14 bit
(164 pm) field (table I, appendix 3) can be estimated:
t,ota,= ntdata + Ntsettle,, = (n -2x 10-'+N
N. 4)sec
6.35cm)2
N= Ato
Afield
-
2
(1642pm)
x0.65mm)
n=N(
20nm
2
31.7cm
2.7 x 10-4 cm
=10 9 N
toa = (24sec)N = 800hrs m 33days
2
1.2 x 105
To estimate the E-beam equipment usage cost per hour, we use JBX-9300FS EBL
System (microelectronic research center, Georgia Tech) as an illustration. The equipment
specifications and its usage cost can be found in appendix 4. It is estimated to be
$1600/hr for industrial usage.
Cost of E-beam equipment usage for pattering a 2.5 disk with 10 nm island size is thus:
800hrsx $1600 / hr = 1.28millon
Plus all the cost, the total cost per one stamp easily exceeds 1 million. Comparing this
value with the total revenue 32.8 billion of the whole HDD industry for year 2007, it can
be concluded that the cost of the stamp is significant.
As calculated based on experimental results, we get total areal density of 648Gb/in 2 by
templated self-assembly of diblock copolymer with inter-groove spacing widths of 100
nm. If we can form smaller domain sizes (imply smaller d), the areal density can be
further increased till comparable with that made by E-beam lithography. While the cost
of this technique is about 50 times lower than E-beam. To estimate the cost of a stamp
made by templated self-assembly of diblock copolymer, we need to know the cost of the
master stamp with spiral patterns. The price of this master with feature size down to 100
nm can be estimated to be around $16,000 according to nanoimprint vendors [65].
Because the materials cost of polymers is not significant (- $300) compared to spiral
patterned master cost, and plus the furnace cost (-$1000), spin coating machine (-$2000)
cost, the total cost will be around $20,000.
6.2. Comparison of Cost: Scheme B) vs. Scheme C)
- Diblock Copolymer vs. Magnetic Nanoparticles
Both technologies use the same concept to achieve well-ordered nanoarrays. Both need
templates/locking patterns to guide the natural self-assembly processes. The difference is
that by scheme c), the magnetic islands assemble in one single step with no nanoimprint
lithography process followed. Self-assembly of diblock copolymer, however, is just used
to fabricate the stamp which is then used to nanoimprint the resist on disk substrate and
finally the pattern is transfer to the magnetic layer by etching, leaving magnetic
nanoarrays. This does not mean that NCs supperlattice is cheaper, because the same set of
nanoimprint lithography steps is still necessary to imprint the groove patterns per one
disk. That means that these two technologies would incur almost the same cost per disk
assuming that no big difference in the materials cost (provided cheap and large amount
supply of NCs). And the throughput may be lower which is limited by the self-assembly
time of NCs.
6.3. Proposed Fabrication Scheme: Scheme B)
Table 6-1 gives a summary of comparison between technologies for making patterned
media discussed above from aspects including cost, throughput, technical barrier and
overall commercialization potential. We can see that scheme B) has medium technical
barrier and is the most promising one for mass fabrication of patterned media when cost
per bit comes into consideration.
1 c•,
v-lu.
Ivllv
at
U3 ~
vi
Lo"ACcullliUSIU~1
patterea
meala Iaoricatlon.
The general fabrication process would be (refer to fig. 6-1): 1) lithographically pattern
the
concentric circular grooves on a mold substrate (can purchase from vendors); 2)
let the
diblock copolymer to self-assembly in the groove, forming islands-in-sea nanostructure;
3) selectively etch away one polymer and transfer the pattern to the stamp substrate;
4)
use the stamper to nanoimprint the patterns onto the PMR disk.
-•
--. ,,
(ion milling) e4:--
mstering by
LBR I EBR
stamper
nann Imnrlntinn
self-assembling
Fig. 6-1: A schematic drawing [17] of patterned media fabrication scheme B), the spiral
patterns on the master stamp can be generated by other lithography methods or purchased
from vendors.
Fig. 6-2: Dots with a diameter of 17 nm imprinted by Obducat's nanoimprint tools
[66].
One problem with templated self-assembly of diblock copolymer as mentioned
previously is that you can not have nanodots on the whole disk surface,
which means that
the spacing land between grooves is a waste. In order to achieve the same
areal density as
whole disk patterning, the island dimension should be reduced by a factor
of 1/f. And
largefapproaching 1 is preferred for higher density. However, large
f means spacing size
as small as possible is required and this requires higher resolution lithography methods
which implies higher cost.
6.4. Cost Modeling for Scheme B)
The throughput of SindreTM nanoimprint tools from Obducat is said to be 1200
disks/hr
which gives a throughput of 10 M disks/year [66]. One nanoimprint tool
costs around
$500,000 for printing areal density of 0.5Tb/in 2 [66]. The cost of the
master stamp with
spiral pattern is $20,000 as estimated before to give disk areal
density of 648Gb / in 2 .
Cost modeling is done for 2.5 inch disks assuming only one nanoimprint
tool is
purchased with the prices of the tool and stamp rise when the areal density
doubles. We
can see that there is a huge potential for patterned media to bring higher
revenue for HDD
industry, provided a successful implementation of our fabrication scheme.
Throughput (million disks/year)
Table 6-2: Cost modeling for 2.5 inch patterned media with
areal densities of 0.5, 1, and
2
2 Tb/in , assuming one nanoimprint system is working.
6 Fixed
cost is estimated by cost per GigaByte (GB)
of the current HDD media which is around I
cents, and
the current PMR areal density of 240Gb/in2
It should be mentioned that similar cost modeling can also be done for scheme A), with
the only difference in master stamp price (change from $20,000 to $1 M). This would
cause the increased revenue to be reduced by $0.98 M, which becomes not so significant
for higher areal density. In other words, although the cost of making the stamp using Ebeam is 50 times more than using templated self-assembled diblock copolymer, it is only
a one time cost which would not be significant for mass production of ultra-high density
patterned magnetic media. That means, even if by scheme A), we can still achieve similar
increase in revenue by implementing patterned media. In fact, in order for patterned
media HDDs to be shipped as soon as possible provided other challenges of head sensor,
flyability and signal processing are all solved, scheme A) can be a choice because more
R&D are needed for templated self-assembly of diblock copolymer as discussed, which is
not expected to be ready before 2011.
7. Patents Relevant to Patterned Media and Fabrication Methods
Intellectual property issues (mainly patent) can be tricky, while it is a must consideration
when doing business. Different countries have different legislation and regulations for
patent. Globalization of business value chain requires careful examination of patent
system in specific countries. Although a patent grants a monopoly, the rights created by a
patent are only valid within the territorial boundaries of the particular nation granting the
patent, absent a treaty between that nation and other countries. To enjoy similar rights in
foreign countries, the inventor must generally obtain separate patents from the
governments of each of those countries. However, some countries are signatories to
regional and international treaties that allow a patent granted by one country to be
enforceable in a several countries [67].
According to US patent law [68], a U.S. patent grants its owner(s) "the right to exclude
others from making, using or selling the invention," within the United States and its
territories for a period of seventeen years. What is granted is not the right to make, use or
sell, but the right to exclude others from making, using or selling the invention. Current
US patent system is first-to-invent rather than first-to-file which quite different from
other countries. However, it is facing transforming to first-to-file. The House version of
the bill Patent Reform Act of 2007 (H.R. 1908, S. 1145) has passed and the Senate version
is under consideration. Patent search on patterned media and fabrication methods from
several patent databases (USPTO, WIPO, EPO, and IPOS etc) was performed and the
most relevant ones are summarized below in table 7-1.
Pulcto
No
US 5587 223
US 6977108 B2
US 7115208 B2
US 7306743 B2
128567
(Application)
Til
sineDt
fptn
Dec. 24, 1996
BOARD OF
TRUSTEES LELAND
STANFORD, JR.
UNIVERSITY
Recording medium including KABUSHIKI KAISHA Dec.20, 2005
patterned tracks and isolated TOSHIBA
regions
High density magnetic
information storage medium
aetofc
------
USPTO
(US)
USPTO
(US)
Method of manufacturing
recording medium
KABUSHIKI KAISHA Oct. 3, 2006
TOSHIBA
USPTO
Recording medium, method
of manufacturing recording
medium and recording
apparatus
Method and apparatus for
manufacturing patterned
KABUSHIKI KAISHA
USPTO
ec. 11, 2007
(US)
TOSHIBA
(US)
KABUSHIKI KAISHA un. 2, 2006
TOSHIBA
(ile date)
IPOS
(Singapore)
SEAGATE
TECHNOLOGY LLC
May 9, 2006
USPTO
SEAGATE
TECHNOLOGY LLC
Dec. 14, 2007
EPO
(European)
INTERNATIONAL
BUSINESS
MACHINES
CORPORATION
HITACHI GLOBAL
STORAGE TECH
Dec. 19, 2000
USPTO
media
US 7041394 B2
Magnetic recording media
having self organized
magnetic arrays
EP1855273 (A2) Data storage device with bit
patterned media with
staggered islands
US 6162532
US 7312939 B2
Magnetic storage medium
formed of nanoparticles
System, method, and
apparatus for forming a
patterned media dish and
related disk drive architecture
for head positioning
EP1710789 (A2) Apparatus, method and
HITACHI GLOBAL
system for fabricating a
STORAGE TECH
patterned media imprint
master
(US)
(US)
Dec. 25, 2007
USPTO
Oct. 11, 2006
EPO
(European)
Table 7-1: List of patents on patterned media and fabrication methods.
(US)
Recall the proposed fabrication scheme for patterned media ("topographically templated
self-assembly of diblock copolymer lithography" for stamp fabrication + nanoimprint
lithography for disk media mass production), we can see that Toshiba owns the most
relevant patent - US 73067h43 B2 [53] and they filed applications both in US (granted)
& in Singapore. However, they only claimed "recording medium including patterned
tracks and isolation regions" and fabrication concept of making the grooves and islands
[52, 53, 69], not "topographically templated
diblock copolymer
self-assembly
lithography". The patents of Toshiba are based on research work of K. Naito et al
mentioned in part 1: technologies [38]. Patent US 7041394 B2 and EP1855273 (A2) of
Seagate is based upon the research work on FePt NCs superlattice mentioned in part 1:
technologies [55]. And US 6162532 by C. T. Black and Shouheng Sun et al is also on
self-assembled magnetic nanoparticles for magnetic recording application [60, 61].
Hitachi's patents (US 7312939 B2) filed both in US and European Union is to lower the
cost of SEBL patterning method for patterned media by making use of the symmetric
geometry of the disk.
Patents on critical technologies for the proposed patterned media fabrication scheme are
summarized in table 7-2:
UNIVERSITY OF
MINNESOTA
i
US 6719915 B2
Step & flash imprint
lithography
US 5948470
US 7347953
g !
Table
•
7-2:
•
Apr. 13, 2004
C. G. Willson
and M. E.
Colburn
Method of nanoscale
NONE
patterning and products made
thereby
Apr. 22, 1998
Harrison et al.
Methods for forming
improved self-assembled
patterns of block copolymers
Mar. 25, 2008
Charles T.
Black, Ricardo
Rulz, and R. L.
Sandstrom
•
T 4
List
of
4
other
REGENTS OF THE
UNIVERSITY OF
TEXAS SYSTEM
a
important
patents
INTERNATIONAL
BUSINESS
MACHINES
CORPORATION
for
patterned
media
fabrication.
One of the first two technologies above [70, 71] (already commercialized) is required for
mass production once we make the stamp using our technology.
Patent US 5948470 is about using diblock copolymer self-assembly to make patterns [72]
which based on the research work of Harrison et al mentioned before [73, 74]. Although
our technology is superior than the one described in the patent, we may need to seek
assistance of a patent lawyer to apply for a new patent or acquire license. The last one is
US 7347953 from C. T. Black et al, which is about self-assembly of block copolymer
restrained in a trench to produce defect-free nanostructures. Although this patent did not
specifically mention the ability to produce controllable nanostructures long-range order
by topographically templated self-assembly of diblock copolymers, it needs to be paid
attention if filing a new patent. It should be mentioned that if apply a new patent, we
should apply internationally, especially in disk manufacturing countries: US, Singapore
& Malaysia.
8. Value Chain and Business Model
8.1. Structure of HDD Value Chain and Our Value Proposition
Hard disk drive (HDD) industry is a very dynamic industry with revenue more than $30
billion. It is an essential component for computer industry (including PC, laptop, and
server) and also becomes important in consumer electronics industry (such as PDA,
digital audio/video players) in recent years.
The main steps in the HDD value chain are summarized in fig. 8-1. The four main
branches in the value chain[75] are: 1) electronic: includes semiconductors, printed
circuit boards (PCBs) and their assembly, 2) heads: devices for read/write the data which
are manufactured with labor-intensive subassembly activities, such as head-gimbal
assembly (HGA) and head-stack assembly (HSA), 3) media: the magnetic disk for storing
the data, 4) motors: mechanical devices to spin the media with extreme precision. Our
technology will generate value in the third branch which is the fabrication of the
recording media.
Component
fabrications
Subassembly
Final
assembly
Motors
Where we
come in
i- Head-disk
assembly
·
-
Head-gimbal
assembly
-+
Head-stack
assembly
Semiconductors, PCB stuffing
and other electronics assembly
Final
assembly
Testing
Fig. 8-1: HDD value chain.
8.2. Globalization of HDD Value Chain
Fifty years ago, most of the production and assembly activities were done in US. The
globalization has rapidly changed the structure of HDD value chain, which now involves
multi-nationals (see fig. 8-2). Producers locate discrete steps in the value chain around
the world for various reasons such as labor cost, policies, intellectual properties etc. We
can identify that the productions of the media disk are mainly located in US, Singapore
and Malaysia. Such globalization phenomenon is important for starting manufacturing
fab and patent applications.
Fig. 8-2 [76]: The globalization of the disk drive supply chain.
8.3. Current HDD Market and Top Players
2007 was a year to remember for HDDs, with shipments reaching
516 million units, up
from 434 million in 2006. Factory revenue rose to $32.8 billion, up
from $31.2 billion in
2006, reported by iSuppli [2]. Traditional HDD markets like
PCs and servers will
continue to grow solidly over the next five years, aided primarily
by demand from
countries such as India and China. And CE (consumer electronics)
markets like personal
video recorders (PVRs), automobile navigation systems, digital audio/video
players and a
host of other devices will together propel the HDD industry
to ship nearly 750 million
drives in 2010, predicted by Trend Focus [3].
iSuppli also reported that Seagate Technology LLC maintained
its lead in the global
HDD market in 2007, with its share of shipments rising
to 34 percent, up from 33.1
percent in 2006. The company shipped 175 million HDDs
in 2007, up 22 percent from
144 million in 2006 [2]. Fig. 8-3 shows the worldwide
HDD shipment share of major
HDD manufacturers in 2007 and table 8-1 summarizes the top three
players with their
2007 shipments and share respectively.
2007 Worldwide HDD Shipment Share
(Percentage of Unit Shipments)
Samsung
Excelstor
1.4%
Tosh
7.2
!agate
3,9%
Fujitsu
6 9%
Hitachi
17.3
,
WDC
22.0%
Fig. 8-3: Worldwide HDD shipment share of 2007
(source: iSuppli [77]).
Rank
Co inpa 11
yIla "Ie
Shipments (Inillion)
I#1
ISeagate Technology LLC (US)
1
I
#2
#3
LI
estern
Digital
Corp
(US)
itachi Global Storage (Japan)
I
1
189
sha re (Iyo)
I~
34
I
122
17.3
Table 8-1: Top three HDD players with their
unit shipments and share of 2007.
8.4. Proposed Business Model and SWOT Analysis
A business model mainly consists of six parts: 1) value proposition: what do we do to
generate value, 2) Target market segments: who are our target customers, 3) Position in
the value chain: what is our function in generating the value in value chain, 4) Cost &
revenue model: how do we generate value, 5) Position in value network: identify our
competitors, partners, and complementors, 6) Competitive strategy: can we compete and
what are our competitive advantages. These six points are addressed respectively below:
1) Value proposition
We produce cheaper nanoimprint stamp and disk of patterned media
2) Target market segments
HDD manufacturers
3) Position in value chain
Patterned media disk supplier
4) Cost & revenue model
Lower the cost of stamps therefore lower the unit cost per media
(Compared with E-beam
lithography and other existing high resolution
lithography techniques)
5) Position in value network
- Competitors
a) Existing competitor: conventional media supplier such as Showa Denko
b) Emerging technology: heat assisted magnetic recording (HAMR)
Mechanisms and problems and HAMR were discussed in chapter 3: competing
technologies. We can see that there remain many issues in this technique such as design a
read/write head integrated with a laser of -20 nm optical spot size, thermally induced
mechanical problem etc. HAMR seems has a long way to come. Even if it does come
before patterned media, it may not become a threat but serve as a milestone as it can be
integrated to patterned media for even higher areal density. Because HAMR only
provides
writable head
for harder
magnetic
materials
which
has
reduced
superparamagnetic limited size and thus it still requires -100 grains per one bit. While
patterned media pattern the magnetic materials to allow one grain for one bit. Therefore,
strictly speaking, HAMR and patterned media are two major proposed technologies for
ultra-high density magnetic storage, and patterned media is more like an ultimate solution
beyond HAMR.
c) Outer competitor: solid state drives (SSD)
As addressed in chapter 3: competing technologies, although SSDs provide some benefits
over HDDs, today's SSDs and are up to 45 times more expensive than rival HDDs and it
is facing scaling challenges with a slower scaling rate than HDDs ( refer to appendix 2).
Alan Niebel, chief executive of Web-Feet Research Inc. put the average price per
gigabyte at $10 for SSDs and 30 cents for hard drives. He said that "If you want to see
big adoption of SSDs, they must hit $1 per gigabyte". Many analysts do not expect
widespread adoption until 2011 or 2012 and by that time, hard drives are expected to cost
a mere 10 cents, and perhaps as little as 3 or 4 cents, per gigabyte of storage, reported in
EE times, 2007 [78].
Currently, most SSDs today are mainly for consumer electronic applications which
require smaller storage capacity, and niche-oriented products for "nontraditional" drive
markets such as the industrial and military sectors, said Jeffrey Janukowicz, an analyst at
International Data Corp. While workhorse hard drives currently and continue to dominate
the laptop, PC and server storage market with areal density increasing at a enormous rate
and a dropping price (see appendix 2), SSDs must make dramatic improvements in both
cost and design, together with a long "education process" before OEMs and end users
understand the benefits before the PC community will consider widespread adoption, said
some analysts [78]. It is also mentioned although SSDs were offered by some PC OEMs
like Dell as an option for their systems, they are much more expensive and are often not
widely advertised by the vendors [78].
- Partners
HDD main players which are also doing relevant R&D: Toshiba, Seagate, Hitachi
- Complementors
Heads manufactures
6) Competitive strategy
- SWOT 7 analysis (refer to table 8-2)
stregth
INYaknsse
Nf
X
Lower technology barrier compared with
competitive technologies
Nt
mt
Can not build up own fab right now - patent
issue and more R&D needed
Capability to improve the technology
X Not a mature technology as E-beam
(reduce the bit size)
lithography, not expected to be ready before
Capability to reduce cost compared to E-
2011
beam (50 times less)
j
Oppo I-tun ities
FirKobust, high revenue HDD market
IThreats
9
I
HDD manufacturers may choose E-beam
Pressing demand of patterned media
lithography instead for faster shipping of
Possible to be granted a patent
patterned media
Collaboration with HDD manufacturers
(virtual vertical integration)
1
Head revolution, flyability, synchronization of
signals and other challenges impede final
HDD assembly production
Table 8-2: SWOT analysis for our business.
From SWOT analysis, we can see that commercialization of our technology has a lot of
strengths and opportunities, however, threats or risks is high too, especially lying in the
technical barrier of complementary technologies like read/write head revolution and
emerging technology such as heat assisted magnetic recording. Also, we need to take
patent issue into consideration as well.
7 SWOT = strength, weakness, opportunity and threat
9. Conclusions
HDD industry is a booming global industry with high revenue, and patterned media is in
pressing need from HDD manufacturers to surpass the scaling limitations. With all the
extensive research effort and achievements on other key complementary technologies
except media fabrication such as head evolution, signal processing, flyability, patterned
media HDD is on its way. Also, discrete track recording technology is under intensive
development, which prepares the way for patterned media. Even if heat assisted magnetic
recording may come out first, it may serve as a milestone towards the realization of
patterned media. This is because patterned media can also be integrated with HAMR to
further increase data storage density just as integration on the recent established
perpendicular magnetic recording. Also, solid state drives will not become a threat of
HDD industry in the next several years because of the much higher price. The future of
HDD future is predicted to be bright provided continues high growth rate in areal density.
In this thesis, we tried to address the media fabrication which is a major challenge left. In
particular, we evaluated three possible fabrication schemes for patterned media, and tried
to lower the fabrication cost by using bottom-up approach (self-assembly) compared with
top-down approach (lithography). The fabrication scheme with the highest potential
considering both technical aspect and economic aspect is to use topographically
templated self-assembly of diblock copolymer to generate the stamp for nanoimprint
followed by mass production enabled by nanoimprint lithography. The cost of the
nanoimprint stamp of patterned media can be lowered by 50 times compared to that
fabricated by electron beam lithography. However, for templated diblock copolymer
self-assembly assisted lithography to be applied in real fabrication of patterned media,
more research needs to be done for optimized diblock copolymer systems: combination
of polymer blocks which gives high X and shorter polymer block lengths (for smaller
domain size), right volume fraction for island-sea phase segregation, good etching
electivity between the two blocks, last but not least, better long-range order. Provided all
these improvement, it is possible to be grant a patent on this technology. It should be filed
especially in disk making countries such as US, Singapore and Malaysia.
To conclude our business model on this technology scheme, we can build up partnership
with large HDD manufacturers (virtual vertical integration) to realize patterned media but
will not build our own fab. This is not only because more R&D work is needed, but also
because large HDD manufacturers are holding critical relevant patents. And the predicted
time for shipment of patterned media would be in 3-5 years.
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
CRC
[17]
[18]
[19]
Andreas Moser, Kentaro Takano, David T Margulies, Manfred Albrecht,
Yoshiaki Sonobe, Yoshihiro Ikeda, Shouheng Sun, and E. E. Fullerton, "Magnetic
recording: advancing into the future," J. Phys. D: Appl. Phys., vol. 35, 2002.
K. Chander, "Storage Exits 2007 with Optimism," iSuppli Corporation 2008.
<http://www.trendfocus.com/>, "TRENDFOCUS," 2008.
C. A. Ross, "PATTERNEDMAGNETIC RECORDINGMEDIA," Annu. Rev.
Mater. Res., vol. 31, pp. 203-35, 2001.
C. Denis Mee and E. D. Daniel, Magnetic Recording Technology: McGraw-Hill
Professional, 1996.
M.L. Plumer, J. van Ek, and D. Weller, The Physics of Ultra-High-Density
Magnetic Recording: Springer, 2001.
Sakhrat Khizroev and D. Litvinov, PerpendicularMagneticRecording: Springer,
2004.
Sadamichi Maekawa and T. Shinjo, Spin Dependent Transport in Magnetic
NanostructuresCRC Press, 2002.
Eric D. Daniel, C. Denis Mee, and M. H. Clark, Magnetic Recording: The First
100 Years: Wiley, 1998.
M. Doerner, B. Xiaoping, M. Madison, T. Kai, P. Qingzhi, A. Polcyn, T.
Arnoldussen, M. F. Toney, M. Mirzamaani, K. Takano, E. Fullerton, D.
Margulies, M. Schabes, K. Rubin, M. Pinarbasi, S. Yuan, M. Parker, and D.
Weller, "Demonstration of 35 Gbits/in² in media on glass
substrates," Magnetics,IEEE Transactionson, vol. 37, pp. 1052-1058, 2001.
Zhong Lin Wang, Yi Liu, and Z. Zhang, HandbookofNanophase and
NanostructuredMaterials Springer, 2002.
B. M. Moskowitz, "Hitchhiker's Guide to Magnetism ": Institute for Rock
Magnetism.
Zhong Lin Wang, Yi Liu, and Z. Zhang, in Handbook ofNanophase and
NanostructuredMaterials.vol. 3 N.Y.: Springer 2002, pp. 247-249.
A. Hubert and R. Schaefer, Magnetic Domains. Heidelberg: Springer-Verlag,
1998.
G. Schmid, Nanoparticles:Wiley-VCH, 2006.
N. A. Kotov, NanoparticleAssemblies and Superstructures
Press, 2005.
A. Kikitsu, Y. Kamata, M. Sakurai, and K. Naito, " Recent Progress of Patterned
Media," Magnetics,IEEE Transactionson, vol. 43, pp. 3685-3688, 2007.
"Hitachi achieves nanotechnology milestone for quadrupling terabyte hard drive,"
Tokyo: Hitachi GST Oct. 15, 2007.
Xiaodong Che, Yawshing Tang, Hyung Jai Lee, Shuyu Zhang, Ki-Seok Moon,
Na-Young Kim, Soo-Youl Hong, Nobuyuki Takahashi, Matthew Moneck, and J.G. Zhu, "Recording Performance Study of PMR Media With Patterned Tracks,"
IEEE TRANSACTIONS ON MAGNETICS, vol. 43, 2007.
[20]
B. Rottmayer, W. A. Challener, J. Hohlfeld, B. Lu, C. Mihalcea, C. Peng, T.
Rausch, and S. A. Seigler, "Heat Assisted Magnetic Recording," in Magnetics
Conference, 2006. INTERMAG 2006. IEEE International,2006, pp. 99-99.
[21]
M. H. Kryder, "Future trends in magnetic storage technology," in Joint NAPMRC
2003. Digest of Technical Papers[PerpendicularMagnetic Recording
Conference 2003], 2003, p. 68.
[22]
L. Hui, L. Bo, H. Ye, and C.Tow-Chong, "HAMR and mechanical stability of its
head-disk interface," in Magnetics Conference, 2005. INTERMAG Asia 2005.
Digests of the IEEE International,2005, pp. 1899-1900.
[23]
W. Peng, Y. T. Hsia, K. Sendur, and T. McDaniel, "Thermo-magneto-mechanical
analysis of head-disk interface in heat assisted magnetic recording," Tribology
International,vol. 38, pp. 588-593, Jun-Jul 2005.
[24]
T. W. McDaniel, W. A. Challener, and K. Sendur, "Issues in heat-assisted
perpendicular recording," Magnetics, IEEE Transactionson, vol. 39, pp. 1972-
[25]
[26]
[27]
1979, 2003.
J. De Blauwe, "Nanocrystal nonvolatile memory devices," Nanotechnology, IEEE
Transactionson, vol. 1, pp. 72-77, 2002.
F. Masuoka, M. Asano, H. Iwahashi, T. Komuro, and S. Tanaka, "A new flash
E2PROM cell using triple polysilicon technology," in Electron Devices Meeting,
1984 International.vol. 30, 1984, pp. 464- 467.
T. Ishii, T. Osabe, T. Mine, F. A. M. F. Murai, and K. A. Y. K. Yano,
"Engineering variations: towards practical single-electron (few-electron)
memory," in Electron Devices Meeting, 2000. IEDM Technical Digest.
International,2000, pp. 305-308.
[28]
K. W. Guarini, C. T. Black, Y. Zhang, I. V. Babich, E. M. Sikorski, and L. M.
Gignac, "Low voltage, scalable nanocrystal flash memory fabricated by templated
self-assembly," in IEDM Tech. Dig., 2003, pp. 22.2.1-22.2.4.
[29]
[30]
[31]
C.T. Black and K. W. Guarini, "Nonvolatile Memory Device Using
Semiconductor Nanocrystals and Methods of Forming the Same," U.S. Patent
7,045,851 B2: International Business Machines Corporation, Armonk, NY, 2006.
H. I. Hanafi, S. Tiwari, and I. Khan, "Fast and long retention-time nano-crystal
memory," Electron Devices, IEEE Transactionson, vol. 43, pp. 1553-1558, 1996.
D. A. Michael, G. Haixiong, W. Wei, L. Mingtao, Y. Zhaoning, D. Wasserman,
S. A. Lyon, and Y. C. Stephen, "Fabrication of 5 nm linewidth and 14 nm pitch
features by nanoimprint lithography," Applied Physics Letters, vol. 84, pp. 5299-
5301, 2004.
[32]
G. z. Cao, Nanostructuresand NanomaterialsSynthesis,Propertiesand
Applications: Imperial College Press, 2004.
[33]
[34]
[35]
Kazuaki Suzuki and B. W. Smith, Microlithography:Science and Technology
CRC Press, 2007.
Mark Mondol and K. Berggren, "Memo on writing time for SEBL in RLE SEBL
facility," in 6.781 lec. notes, chapter 15: Research Laboratory of Electronics,
MIT, p. 22.
C. M. S. Torres, "Alternative Lithography: Unleashing the Potentials of
Nanotechnology ": Springer, 2004.
[36]
Rachid Sbiaa and S. N. Piramanayagam, "Patterned Media Towards Nano-bit
Magnetic Recording: Fabrication and Challenges," Recent Patents on
Nanotechnology vol. 1, 2007.
[37]
[38]
S. Y. Chou, "Nanoimprint lithography ":Regents of the University of Minnesota,
1995.
Katsuyuki Naito, Hiroyuki Hieda, Masatoshi Sakurai, Yoshiyuki Kamata, and
Koji Asakawa, "2.5-inch disk patterned media prepared by an artificially assisted
self-assembling method," Magnetics, IEEE Transactionson, vol. 38, pp. 1949-
[39]
1951, 2002.
F. S. Bates and G. H. Fredrickson, "Block Copolymer Thermodynamics: Theory
and Experiment," Annual Review of PhysicalChemistry, vol. 41, pp. 525-557,
1990.
[40]
[41]
[42]
[43]
I. W. Hamely, The Physics of Block Copolymers: New York: Oxford Univ. Press,
1998.
R. A. Segalman, A. Hexemer, R. C.Hayward, and E. J.Kramer, "Ordering and
Melting of Block Copolymer Spherical Domains in 2 and 3 Dimensions,"
Macromolecules,vol. 36, pp. 3272-3288, 2003.
M. Park, C. Harrison, P. M. Chaikin, R. A. Register, and D. H. Adamson, "Block
Copolymer Lithography: Periodic Arrays of -10 11 Holes in 1 Square
Centimeter," Science, vol. 276, pp. 1401-1404, May 30, 1997 1997.
M. W. Matsen and M. Schick, "Stable and unstable phases of a diblock copolymer
melt," Physical Review Letters, vol. 72, p. 2660, 1994.
[44]
[45]
[46]
[47]
[48]
[49]
[50]
S. Ouk Kim, H. H. Solak, M. P. Stoykovich, N. J.Ferrier, J. J.de Pablo, and P. F.
Nealey, "Epitaxial self-assembly of block copolymers on lithographically defined
nanopatterned substrates," Nature, vol. 424, pp. 411-414, 2003.
R. A. Segalman, H. Yokoyama, and E. J.Kramer, "Graphoepitaxy of Spherical
Domain Block Copolymer Films," Advanced Materials,vol. 13, pp. 1152-1155,
2001.
X. M. Yang, R. D. Peters, P. F. Nealey, H. H. Solak, and F. Cerrina, "Guided selfassembly of symmetric diblock copolymer films on chemically nanopatterned
substrates," Macromolecules, vol. 33, pp. 9575-9582, 2000.
Paul F. Nealey, Juan J.DePablo, Francesco Cerrina, Harun H. Solak, XiaoMin
Yang, Richard D. Peters, and Q.Wang, "Guided self-assembly of block
copolymer films on interferometrically nanopatterned substrate, US 6746825 B2,"
Wisconsin Alumni Research Foundation, Jun. 8, 2004.
J. Y. Cheng, C. A. Ross, E. L. Thomas, H. I. Smith, and G. J. Vansco,
"Fabrication of nanostructures with long-range order using block copolymer
lithography," Applied Physics Letters, vol. 81, pp. 3657-3659, 2002.
J. Y. Cheng, A. M. Mayes, and C. A. Ross, "Nanostructure engineering by
templated self-assembly of block copolymers," Nat Mater, vol. 3, pp. 823-828,
2004.
J.Y. Cheng, C.A. Ross, E.L. Thomas, H.I. Smith, and G.J. Vancso, "Templated
Self-Assembly of Block Copolymers: Effect of Substrate Topography," Advanced
Materials,vol. 15, pp. 1599 - 1602, 2003.
[51]
[52]
[53]
[54]
[55]
[56]
[57]
[58]
[59]
[60]
[61]
[62]
[63]
[64]
[65]
[66]
[67]
Hiroyuki Hieda, Masatoshi Sakurai, Koji Asakawa, Toshiro Hiraoka, and K.
Naito, "Recording medium including patterned tracks and isolation regions, US
6977108 B2," Kabushiki Kaisha Toshiba, Dec. 20, 2005.
Hiroyuki Hieda, Masatoshi Sakurai, Koji Asakawa, Toshiro Hiraoka, and K.
Naito, "Method of manufacturing recording medium, US 7115208 B2,"
KABUSHIKI KAISHA TOSHIBA, Oct. 3, 2006.
Hiroyuki Hieda, Masatoshi Sakurai, Koji Asakawa, Toshiro Hiraoka, and K.
Naito, "Recording medium, method of manufacturing recording medium and
recording apparatus, US 7306743 B2," KABUSHIKI KAISHA TOSHIBA,
Dec. 11, 2007.
M. D. Bentzon, J. V. Wonterghem, S. Morup, A. Thoelen, and C. J. W. Koch,
"Ordered aggregates of ultrafine iron oxide particles: 'Super crystals'," Phil.
Mag., vol. B60, pp. 169-178, 1989.
Shouheng Sun, C. B. Murray, Dieter Weller, Liesl Folks, and Andreas Moser,
"Monodisperse FePt Nanoparticles and Ferromagnetic FePt Nanocrystal
Superlattices," Science, vol. 287, 2000.
R. W. Chantrell, D. Weller, T. J. Klemmer, S. Sun, and E. E. Fullerton, "Model of
the magnetic properties of FePt granular media," 2002, pp. 6866-6868.
Dieter Klaus Weller, Neil Deeman, Rene Johannes Marinus van de Veerdonk, and
Nisha Shukla, "Magnetic recording media having self organized magnetic arrays,"
US 7041394: Seagate Technology 2006.
K.-E. Kim, M.-K. Lee, Y.-M. Sung, and T. G. Kim, "Enhanced Ll [sub 0]
chemical ordering and FePt/Fe[sub 3]O[sub 4] core/shell structure formation in
Zn-doped FePt nanoparticles," Applied Physics Letters, vol. 90, pp. 173117-3,
2007.
S.Yamamoto, Y. Morimoto, T. Ono, and M. Takano, "Magnetically superior and
easy to handle Ll [sub 0]-FePt nanocrystals," Applied Physics Letters, vol. 87, pp.
032503-3, 2005.
C. T. Black, C. B. Murray, R. L. Sandstrom, and S. Sun, "Spin-Dependent
Tunneling in Self-Assembled Cobalt-Nanocrystal Superlattices," Science, vol.
290, pp. 1131-1134, November 10, 2000 2000.
Charles T. Black, Stephen M. Gates, Christopher B. Murray, and S. h. Sun,
"Magnetic storage medium formed of nanoparticles, US 6162532," International
Business Machines Corporation, Dec 19, 2000.
M. LaPedus, "Nano-imprint litho tool shipped to Toshiba " in EE Times
01/11/2007 1:36 PM EST.
M. LaPedus, "Second impression for nanoimprint " in EE Times 06/11/2007 9:00
AM EDT.
<http://en.wikipedia.org/wiki/E-beam lithography>, "Electron beam
lithography," Wikipedia, the free encyclopedia.
<http://www.nilt.com/Default.asp?Action=Details&Item=282>, "NIL Technology
Website."
<http://www.obducat.se/Default.aspx?ID=489>, "Obducat Website."
<http://www.wipo.int/portal/index.html.en>, "World Intellectual Property Office
official website."
[68]
[69]
[70]
[71]
[72]
[73]
[74]
[75]
<http://www.uspto.gov/web/patents/legis.htm>, "United States Patents and
Trademark Office."
Hiroyuki Hieda, Masatoshi Sakurai, Koji Asakawa, Toshiro Hiraoka, and K.
Naito, "Recording medium including patterned tracks and isolation regions,"
GI 1B005/73; Gi1B005/31 ed: Kabushiki Kaisha Toshiba, 2005.
S. Y. Chou, "Nanoimprint lithography, US 5772905 ": Regents of the University
of Minnesota, Nov. 15, 1995.
C. G. Willson and M. E. Colburn, "Step & flash imprint lithography, US 6719915
B2," Regents of the University of Texas System, Apr. 13, 2004.
Christopher Harrison, Miri Park, Richard Register, Douglas Adamson, Paul
Mansky, and P. Chaikin, "Method of nanoscale patterning and products made
thereby, US 5948470," Sep. 7, 1999.
C. Harrison, "Mechanisms of ordering in striped patterns," Science, vol. 290, pp.
1558-1560, 2000.
M. Park, C. Harrison, P. M. Chaikin, R. A. Register, and D. H. Adamson, "Block
copolymer lithography: periodic arrays of [sim]1011 holes in I square
centimeter," Science, vol. 276, pp. 1401-1404, 1997.
teven Brakman, Harry Garretsen, and Charles van Marrewijk, An Introduction to
GeographicalEconomics: Trade, Location and Growth: Cambridge University
[76]
Press, 2001.
R. de Souza and K. Heng Poh, "Supply chain models in hard disk drive
manufacturing," Magnetics, IEEE Transactionson, vol. 35, pp. 950-955, 1999.
[77]
[78]
<http://www.isuppli.com/>, "iSuppli Corporation: Applied Market Intelligence."
Mark LaPedus and R. Merritt, "Solid-state drives aim at HDDs' heart," in EE
Times 11/30/2007 3:00 PM EST.
Appendices
Appendix 1: Trends and future prediction of HDD industry
DISK DRIVE SALES GROWTH
$billions)
50
40
30
20
10
0
-10
-20
2000
2001
2002
2003
2004
2005 2006" 2007
2008
2Q009" 2010*
20042010 CAGR: 10.04%
SForecast
10,000
40%/vt
1,000
240
C
Gb/in 2
d
100
Perpendicular
10
C
4,
45
43
I-
C
0.1
Thin-film disk
(001
,C1
1980
1990
2000
2010
Bit oreal density of magnetic recording disks for spin stand demonstrations and for
commercial ooducs. Ptterned media market entry is
exocted inthe 2010-20 1timefraome.
Source: Hitachi Global
Appendix 2: Comparisons of SSD and HDD
Areal Density of Magnetic HDD and DRAM
6
3
10
2
10
10
I
-1
10
1970
1980
1990
Year
Source: Hitachi Global
2000
2010
Ed Grochowaskiid
1UU
10
1
0.1
0.01
0.001
0.0001
1990
1995
2000
Year
Source: Hitachi Glob al
2005
Ed Grochowski
2010
Markets and Applications of HDDs
N"fl
Handheld
Education-use
coputing
de>vices
WaI-
a
Various built-inHDDs
/ I,,
-~·s
I.
rnllý
atile disk for removable usagc
Source: Hitachi Global
Some performance benefits of SSD over HDD
Total notebook
shipments,
millions of units
SSD
penetration
rate
4)
NANDflash based
2009
175
r1
15%
Penetration of solid state drives (SSs innotebook
PCs se laking off.
Source: EE times
640B
79
Rea
10C0MB/;Wtal
Mecatam type
oens•ny
Weigl
:80Nts
Perfornance
IW
Active Power consumption
200 (10200W0)
1:5000 for 0Sms
Operating Vibration
Shock resistance
Operating temperature
Acouski Noise
Endurance
0%Cto 70*C
Nobne
MTBF>2M hoirs
Source: Samsung
Manr
rotafIg platters
80o
Read, 59MBis, V
60MB/s
86W
0.50 (22-35z)
1700 for 0.5ms
5C to 55C
03 dB
MTBF r 07M hours
Appendix 3: SEBL parameters
A field
Table I: Pixel size and field size
Address grid
Period
digital field
actual field size
(pnm)
(nim)
100
10
10
10
1
12 bit (4096)
12 bit (4096)
14 bit (16,384)
16 bit (65,536)
16 bit (65,536)
410
41
164
655
66
Table II: Time per pixel and pixel transfer rate
RESIST SENSITIVITY
CURRENT DENSITY
1 A/cm 2
2
10 A/cm-'
100 A/cm 2
1000 A/cm 2
10,000
A/cm
10-4 sec
10' sec
10" sec
(10 kHz)
(100 kHz)
(1 MHz)
10- see
10" sec
10"
(100 kHz)
(1 MHz)
(10 MHz)
10" sec
10f' sec
10-" sec
(1 MHz)
(10 MHz)
(100 MHz)
10'" sec
10" sec
10- sec
(10 MHz)
(100 MHz)
(1GHz)
sec
o10
10- sec
10-lu sec
(1Ghz)
(10GHz)
(100 MHz)
sec
Table III: Date rate
Data Rate
SEBL Type
10-100 kHz
Converted SEM
Raith 150 (converted Leo SEM)
1 MHz
JEOL model JBX 5DII
2 MHz
VS-26, at MIT (converted IBM systems)
6 MHz
10 MHz
EBPG (Leica)
Nanowriter (Lawrence Berkeley Lab, 1996)
100 MHz
VB-6 (Leica)
100 MHz
160 MHz
MEBES IV, Etec Systems
Considering that many research-grade tools operate at
a ~ 10 MHz data
rate, but have current densities of ~ 1000 A/cm , for sensitive resists, these
tools are typically limited by the data rate, not by resist sensitivity.
Source: Karl K. Berggren, 6.781 lee. notes (MIT), chapter 15, P20
Appendix 4: JBX-9300FS EBL system specification and charge
JEZL
JBD-93U7 j
n
"FVEDBL
V0
S+tm
ysemt
jeolebeam-users(@grover.mirc.gatech.edu
Nanolithography at Tech
-4 nm diameter Gaussian spot electron beam
-50 kV/100 kV accelerating voltage
-50 pA - 100pA current range
-50 MHz scan speed
- +/- 10Oum vertical range automatic focus
- +/- 2mm vertical range manual focus
- ZrO/W thermal field emission source
-vector scan for beam deflection
-max 300 mm (12") wafers with 9" of writing area
- < 20 nm line width writing at 10kV
- < 20 nm field stitching accuracy at 100kV
- < 25 nm overlay accuracy at 100 kV
Source: http://grover.mirc.gatech.edu/equipment/index.php?id
=
131
JBX-9300FS usage costs:
The MiRC began charging for EBL usage on July 1, 2006. The email announcing the
charge rates and an explanation of how charging is determined can be found here.
The following charges apply when an individual operates the JBX-9300FS.
$130/hr + overhead
Georgia Tech Researchers
Other Academic Researchers $130/hr + overhead
$975/hr + overhead
Industrial Rate
The following additional charges apply when an individual is not trained to operate the
JBX-9300FS and staff perform the work instead.
$52/hr + overhead
Georgia Tech Researchers
Other Academic Researchers $52/hr + overhead
$52/hr + overhead
Industrial Rate
Overhead rates are as follows:
36.3% for University System of GA (USG) institutions
51.0% for non-USG Universities and non-DOD federal
55.5% for DOD
55.7% for Industry
Source: http://nanolithography.gatech.edu/services.html
Total cost per hour: ($975 + $52) x (1+ 55.7%) = $1600
Appendix 5: Patent on patterning/lithography method by self-assembly
of block copolymers
111
111
111111111
Iillll~i1111
I IliEIII
IM 1111111
USUU.9464 /UA
United States Patent [19]
Harrison et al.
[54]
[76]
[*]
METHOD OF NANOSCALE PATTERNING
AND PRODUCTS MADE THEREBY
Inventors: Christopher Harrison, 807 Lake View
Ter., Princeton, N.J. 08540; Miri Park,
8532 Town Ct. N., Laurenceville, NJ.
08648; Richard Register, 1 Sarah Dr.,
Princeton Junction, N.J. 08550; Douglas
Adamson, 348 Grandview Rd.,
Skillman, N.J. 08558; Paul Mansky, 33
Meadow St., Apt. A, Amherst, Mass.
01002; Paul Chaikin, 121 Blackwell
Rd., Pennington, N.J. 08534
Notice:
This patent issued on a continued prosecution application filed under 37 CFR
1.53(d), and is subject to the twenty year
patent term provisions of 35 U.S.C.
154(a)(2).
[21] Appl. No.: 09/064,274
[22] Filed:
[60]
Apr. 22, 1998
Related U.S. Application Data
Provisional application No. 60/045,019, Apr. 28, 1997.
Int. CI. 6 .............................. .................... . . B05D 5/00
U.S. Cl. ................... 427/198; 427/430.1; 156/659;
156/654; 156/656
[58] Field of Search .............................. 156/60, 628, 635,
156/638, 644, 654, 646.1, 654.1, 656.1,
659.11, 643, 646, 659.1, 630, 633, 657,
660, 667, 659, 656; 427/180, 183, 43.1,
189, 195, 197, 198, 220, 221, 272, 282,
430.1
[51]
[52]
[11] Patent Number:
[45] Date of Patent:
[56]
5,948,470
*Sep. 7, 1999
References Cited
U.S. PATENT DOCUMENTS
4,407,695 10/1983 Deckman et al. .................. 156/643
4,512,848 4/1985 Deckman et al. ................... 156/630
4,801,476 1/1989 Dunsmuir et al. .................... 427/430.1
OTHER PUBLICATIONS
Chou, S., "Single-domain magnetic pillar array of 35 nm
diameter and65 Gbits/in. 2 density for ultrahigh density
quantum magnetic storage", J. Appl. Physics 1994 76:6673.
Douglas et al., "Transfer of Biologically Derived Nanometer-Scale Patterns to Smooth Substrates", Science 1992
257:642.
Kryder, M.H., "Magnetic thin films for data storage", Thin
Solid Films 1992 216:174.
Tonucci et al., "Nonochannel Array Glass", Science 1992
258:738.
Volkmuth, W.D. and Austin, R.P.H., "DNA electrophoresis
in microlithographic arrays", Nature 1992 358:600 1992.
PrimaryExaminer--Merrick Dixon
Attorney, Agent, or Firm--Law Offices of Jane Massey
Licata
[57]
ABSTRACT
Methods of nanometer pattern formation and transfer onto a
selected substrate are provided wherein a selected block
copolymer is coated onto the selected substrate and a
component of the block copolymer is chemically modified
or physically removed so that the dense periodic pattern of
the block copolymer can be transferred onto the selected
substrate. Substrates prepared by these methods are also
provided.
2 Claims, No Drawings
Appendix 6: Patent on patterned media
I1IIIII
11 1111
11
11 11111I Ii1111
UII III II1111
I II111
US005587223A
United States Patent
[11]
[45]
White
[54]
HIGH DENSITY MAGNETIC INFORMATION
STORAGE MEDIUM
[75]
Inventor: Robert L. White, Stanford, Calif.
[73]
Assignee: Board of Trustees Leland Stanford,
Jr.University, Stanford, Calif.
[21]
Appl. No.: 270,201
[22]
Filed:
Jun. 30, 1994
Continuation of Ser. No. 963,562, Oct. 19, 1992, abandoned.
[51]
[52]
Int. Ci.L .............................
G11B 5/66; B32B 3/00
U.S. Cl ....................... 428/195; 428/218; 428/692;
428/694 R; 428/694 ' 428/694 TR; 428/336;
428/900; 427/128; 427/130; 283/82
Field of Search .................................... 428/195, 218,
428/692, 694 R, 900, 694 T, 694 TR; 283/336,
82; 427/128, 130
References Cited
U.S. PATENT DOCUMENTS
6/1981 Schmelzer ..............................
Iii
Iii
ii
Ii
6/1987 Sakurai ...................................
428/606
5/1988 Bishop et al. ....................... 428/557
6/1990 Krounbi ..............
428/65.5
FOREIGN PATENT DOCUMENTS
99253 3/1992 Japan.
84403 3/1992 Japan.
[571
[63]
4,274,935
4,670,353
4,746,580
4,935,278
Dec. 24, 1996
Primary Examiner-Leszek Kiliman
Attorney, Agent, or Firm--ClaudeA.S. Hamrick
Related U.S. Application Data
[58]
5,587,223
Patent Number:
Date of Patent:
II
II
II
II
365/50
ABSTRACT
Magnetic recording media comprising an ordered, ultra-high
density array of 500 A diameter circular magnetic thin film
islands on a substrate. The magnetic material supports
magnetization perpendicular to the film plan, and each
circular island comprises a single magnetic domain and a
single 2information storage bit. An areal bit density of 10"1
bits/in can be achieved by such an array. The magnetic
array is generated using a single level mask comprised of a
self-ordering polymer array, either an array of polymer
spheres or a regular array of polymeric blocks in a phaseseparating polymer film.
14 Claims, 2 Drawing Sheets
I
I
I-------------------
II
II
I
I
Appendix 7: Toshiba's pattern on patterned media and fabrication
method of forming islands in tracks/grooves
111111
I111111111111111111111I
IIIIN11111111
Ii
US007306743B2
(12) United States Patent
(10) Patent No.:
US 7,306,743 B2
*Dec. 11, 2007
(45) Date of Patent:
Hieda et al.
(54)
RECORDING MEDIUM, METHOD OF
MANUFACTURING RECORDING MEDIUM
AND RECORDING APPARATUS
(52) U.S. C. .......................... 216/22; 216/41; 430/312;
430/322; 428/64.2; 29/603.01; 29/603.03
(58) Field of Classification Search .................. 216/22,
216/41,42; 428/64.2; 360/313; 29/603.01,
29/603.03
See application file for complete search history.
(75) Inventors: Hiroyuki Hieda, Yokohama (JP);
Masatoshi Sakural, Tokyo (JP); Koji
Asakawa, Kawasaki (JP); Toshiro
Hiraoka, Fujisawa (JP); Katsuyuki
Naito, Tokyo (JP)
(73)
(21)
4,052,711 A
(Continued)
FOREIGN PATENT DOCUMENTS
This patent is subject to a terminal disclaimer.
(Continued)
62-202303
U.S. Appl. No. 10/786,290, filed Feb. 26, 2004, Fujimoto, et al.
(Continued)
Jul. 27, 2006
Primary Examiner--Shamim Ahmed
Prior Publication Data
US 2006/0263642 Al
Nov. 23, 2006
(74) Attorney, Agent, or Firm-Oblon,Spivak, McClelland,
Maier & Neustadt, P.C.
Foreign Application Priority Data
(51)
Int. Cl.
B44C 1/22
GlIB 5/127
(JP)
ABSTRACT
(57)
(62) Division of application No. 11/000,170, filed on Dec.
1, 2004, now Pat. No. 7,115,208, which is a division
of application No. 10/102,812, filed on Mar. 22, 2002,
now Pat. No. 6,977,108.
Mar. 22, 2001
9/1987
OTHER PUBLICATIONS
Related U.S. Application Data
(30)
10/1977 Lin et al.
Subject to any disclaimer, the term of this
patent is extended or adjusted under 35
U.S.C. 154(b) by 0 days.
Appl. No.: 11/493,807
(22) Filed:
(65)
U.S. PATENT DOCUMENTS
Assignee: Kabushiki Kaisha Toshiba, Tokyo (JP)
( *) Notice:
References Cited
(56)
......................... 2001-082436
A recording medium includes a substrate, and a recording
layer formed on the substrate having (a) a recording track
band, and (b)recording cells regularly arrayed in the recording track band to form a plurality rows of sub-tracks. The
recording cells included in each sub-track are formed apart
from each other at a pitch P in the track direction. Nearest
neighboring two recording cells, each positioned on adjacent
two sub-tracks in the track band, are formed apart from each
other at a pitch P/n in the track direction, where 25n55.
(2006.01)
(2006.01)
10 Claims, 20 Drawing Sheets
V
24
aq
--
xXt
a1
',
T
KZZZZZZ222__21
S.1 2-2
21
Appendix 8: Seagate's patent on NCs superlattice technology for
patterned media
II1 IIIIIIIIIIIIIImlIIII III
IIIIIIII 1IIll
US007041394B2
(12)
United States Patent
(10) Patent No.:
Weller et al.
(45) Date of Patent:
(54)
MAGNETIC RECORDING MEDIA HAVING
SELF ORGANIZED MAGNETIC ARRAYS
(75)
Inventors: Dieter Klaus Weller, Gibsonia, PA
5,851,644
5,851,656
5,942,342
5,965,194
5,981,053
5,993,956
5,998,002
6,162,532
6,262,129
6,265,021
6,541,386
6,562,633
6,602,620
2001/0006744
2002/0145826
2003/0222048
(US); Neil Deeman, Alamo, CA (US);
Rene Johannes Marinus van de
Veerdonk, Pittsburgh, PA (US); Nisha
Shukla, Pittsburgh, PA (US)
(73)
Assignee: Seagate Technology LLC, Scotts
Valley, CA (US)
( *)
Notice:
(21)
Appl. No.: 10/005,244
(22)
Subject to any disclaimer, the term of this
patent is extended or adjusted under 35
U.S.C. 154(b) by 79 days.
Filed:
JP
(51)
12/2000
7/2001
7/2001
4/2003
5/2003
8/2003
7/2001
10/2002
12/2003
2000-311448
* 7/2000
OTHER PUBLICATIONS
Sep. 19, 2002
S.H. Charap, Pu-Ling Lu and Yanjun He Thermal Stability
of Recorded Information at High Densities IEEE Transactions on Magnetics, vol. 33, No. 1, Jan. 1997.
Related U.S. Application Data
(60)
12/1999
Provisional application No. 60/275,969, filed on Mar.
15, 2001.
(Continued)
Primary Examiner-Kevin M. Bernatz
(52)
Int. CIL
GllB 5/64
U.S. Cl. .........
(58)
Field of Classification Search ............. 428/836,
(74) Attorney, Agent, or Firm-BuchananIngersoll PC
(2006.01)
428/836; 428/836.1; 428/848.1
(57)
428/836.1, 848.1
See application file for complete search history.
References CIted
A
A
A
A
A
4/1987
8/1992
5/1993
10/1995
2/1997
Mallory
Daimon et al. ............ 428/402
Ito et al.
Grill at al. ................. 428/65.5
Visokay at al.
X X
.
ABSTRACT
A magnetic recording disc is provided according to the
present invention for magnetic recording. The magnetic
recording disc includes a disc substrate having a locking
pattern etched therein. Chemically synthesized iron-platinum particles are provided in the locking pattern and completely fill the locking pattern. The chemically synthesized
iron-platinum nanoparticles exhibit short-range order characteristics forming self organized magnetic arrays.
U.S. PATENT DOCUMENTS
4,656,546
5,139,884
5,210,673
5,462,784
5,603,766
McArdle et al. ............ 428/213
Ohkubo
Hikosaka et al.
Tmuong ct al.
Naylor et al. ............ 428/323
Lambeth etal.
Harada et al.
Black et al ................. 428/323
Murray et al. ................ 516/33
Black et al.
Aiba et al. ................. 438/707
Misewich et al. ............. 438/3
Kikitsu et al. ........... 428/694 T
Saito ................. 428/694 TM
Zangari et al. ............. 360/135
Asakawa et al. .......... 216/2
(Continued)
Prior Publication Data
US 2002/0132083 Al
12/1998
12/1998
8/1999
10/1999
11/1999
11/1999
May 9, 2006
FOREIGN PATENT DOCUMENTS
Dec. 3, 2001
(65)
A *
A
A
A
A *
A
A
A *
B *
BI
BI*
BI *
BI *
Al*
Al*
Al*
US 7,041,394 B2
15 Claims, 5 Drawing Sheets
al
0%0%
AA
2
0I