High-K Dielectric Materials
In Microelectronics
NAME: Neha Tomar
IIT GUWAHATI
OUTLINE
INTRODUCTION
MOORE’S LAW AND TRANSISTOR SCALING
WHY HIGH-K DIELECTRICS?
APPLICATIONS IN MICROELECTRONICS
HIGH-K DIELECTRICS IN DRAMS
HIGH-K GATE DIELECTRICS
SUMMARY
HIGH-K DIELECTRICS IN MICROELECTRONICS
INTRODUCTION
MOORE’S LAW
A prediction made by Mr. Gordon Moore
that the number of transistors on a chip double every two years.
HIGH-K DIELECTRICS IN MICROELECTRONICS
INTRODUCTION
•Transistor
physical
gate length
will reach
~15nm
before
end of this
decade, and
~10nm early
next decade
HIGH-K DIELECTRICS IN MICROELECTRONICS
INTRODUCTION
PROBLEM AS TRANSISTOR IS MADE
SMALLER.
‰Gate dielectric ,Silicon dioxide are only a few atomic layers
thick now.
‰ Leakage current increases, as thickness decreases.
A New dielectric material is needed to reduce leakage current.
HIGH-K DIELECTRICS IN MICROELECTONICS
INTRODUCTION
WHAT ARE HIGH-K MATERIALS?
‰ Thicker class of material known as “High-K” is likely to
replace Silicon oxide.
‰ K stands for dielectric constant, a measure of how much
charge a material can hold.
HIGH-K DIELECTRICS IN MICROELECTONICS
INTRODUCTION
HIGH-K MATERIAL BENEFITS
Sio2
Capacitance 1*
Leakage
1*
High-k
1.6*
< 0.01*
HIGH-K DIELECTRICS IN MICROELECTONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K GATE STACKS
TRANSISTOR
A simple switch
Current flows source to
drain when a certain
Voltage is applied on
The gate, otherwise
Doesn’t flow.
Schematic of important regions
Of field effect transistor
gate stack
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K GATE STACKS
Scaling limits for current Gate Dielectrics
‰ Silicon dioxide is current gate dielectrics
‰ Sio2 thickness can’t be
decreased less than
1-1.5nm, because
leakage current
increases
‰ So, Continual scaling.
will require high-K
material for dielectric
layer.
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K GATE STACKS
ALTERNATIVE HIGH-K GATE DIELECTRICS
‰Metal oxides of ZrO2, HfO2, Y2O3 and Al2O3
High-K Dielectric Leakage
material constant Current
reduction
ZrO2
~23
*104-105
HfO2
~20
*104-105
Y2O3
~15
*104-105
Al2O3
~10
*102-103
Thermal
stability
Tmax ‘c
~900
~950
Silicate
formation
~1000
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K GATE STACKS
ALTERNATIVE HIGH-K GATE DIELECTRICS
‰Pseudo binary materials
(HfO2)x (SiO2)1-x and (ZrO2)x(SiO2)1-x
‰Silicate-Si
interface
is chemically similar
to the SiO2-Si
Interface.
‰Low
defect densities
Hf-silicate between Si layer
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K GATE STACKS
ALTERNATIVE HIGH-K GATE DIELECTRICS
‰Pseudo binary materials
(HfO2)x (SiO2)1-x and (ZrO2)x(SiO2)1-x
‰Silicate-Si
interface
is chemically similar
to the SiO2-Si
Interface.
‰Low
defect densities
Hf-silicate between Si layer
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K GATE STACKS
KEY GUIDELINES FOR SELECTING AN ALTERNATIVE
GATE DIELECTRIC
‰Interface quality
‰Permittivity and band gap
‰Thermodynamic stability
‰Compatibility with the current or expected materials
to be used in processing for CMOS devices
‰ Reliability
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K GATE STACKS
PROCESS ISSUES THAT AFFECT DEVICE
‰Pre-deposition treatments
HF last,O3 etc.
‰Pre/post-deposition
annealing
O2 and N2 annealing
etc.
‰High-k deposition
ALD,CVD etc.
‰Gate electrode
metal gates, poly-silicon
gates etc.
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K GATE STACKS
GATE ELECTRODE
PROBLEMS WHEN SiO2 IS REPLACED WITH HIGH-K
Problems arise due to interaction with the Poly-Si gate
‰Phonon Scattering –electrons slow down
‰Threshold voltage pinning-Due to defects that arise at the
gate-dielectric/gate electrode
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K DIELECTRICS IN DRAMS
GATE ELECTRODE
SOLUTION-METAL GATE
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K GATE STACKS
STATE-OF-THE-ART TRANSISTOR
Metal gate and high-K dielectric transistor offer
the promise toward CMOS Technology nodes.
Other technologies are also emerging for low-power
and high-performance logic.
For example
Nanoelectronic devices, SOI, double gate
and tri-gate etc.
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K DIELECTRICS FOR DRAMS
WHAT IS DRAM?
DRAM is a type of
random access
memory that stores
each bit of data in a
separate capacitor.
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K DIELECTRICS FOR DRAMS
‰The continuous “shrinking technology” up to Gbit density
exposes many challenges.
‰Sio2 can not be made thinner any more.
‰Alternative dielectric having a substantially higher permittivity
is needed for further high density DRAMs.
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K DIELECTRICS FOR DRAMS
ALTERNATIVE HIGH-K DIELECTRICS FOR DRAMS
Among this, BST film is the most promising capacitor
material in future DRAM applications.
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K DIELECTRICS FOR DRAMS
BST capacitor structure
with the stacked barrier
scheme.
Cross-section TEM
Image of a stacked-capacitor
Structure with a BST dielectric
Pt electrode and a TaSiN
barrier layer.
Minimum feature size=0.2um
Dielectric thickness=27 nm
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K DIELECTRICS FOR DRAMS
Factors that influence BST thin film properties
‰Processing methods
‰Film composition
‰Crystalline structure
‰Microstructure
‰Surface morphology
‰Film thickness
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K DIELECTRICS FOR DRAMS
Process Integration
Main Points
‰ BST deposition techniques
‰ Electrode material & Barriers
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K DIELECTRICS FOR DRAMS
Process Integration
BST deposition techniques
Main techniques
MOCVD
rf-sputtering
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K DIELECTRICS FOR DRAMS
Process Integration
ELECTRODE MATERIAL
Noble metals
Exp-Pt, Ru etc
•Low leakage
current
Conducting
Oxides
Exp-Iro2 etc
•High leakage
current
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K DIELECTRICS FOR DRAMS
Process Integration
Various integration schemes for BST capacitor
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K DIELECTRICS FOR DRAMS
Last but not least
Reliability
Time to breakdown
Ba0.47Sr0.53TiO3 at
various OMR
Time to breakdown Ba0.47Sr0.53TiO3
Deposited on various electrodes
TDDB for various DRAM dielectrics
HIGH-K DIELECTRICS IN MICROELECTRONICS
APPLICATIONS IN MICROELECTRONICS
HIGH-K DIELECTRICS FOR DRAMS
High-k dielectrics (BST film ) has become the dielectric
material of choice for cell capacitor of the dynamic
random access memory devices (DRAMs) having gigabit
densities
To continue “shrinking technology” , BST thin films will
be a productive field of research and development.
HIGH-K DIELECTRICS IN MICROELECTRONICS
SUMMARY
To continue Moore’s law for next decades,
New materials are needed.
High-k dielectrics may ultimately lead to vaster
and enable applications.
Industry is seeking for new materials and
technologies that can replace SiO2 and scaling
remains continue.
HIGH-K DIELECTRICS IN MICROELECTRONICS
References
1. H.R. Huff , A. Hou, C. Lim, Y. Kim, J. Barnett, G. Bersuker, G.A Brown, C.D.
Young,P.M. Zeitzoff, J. Gutt, P. Lysaght, M.I. Gardner, R.W. Murto
” High-k gate stacks for planar, scaled CMOS integrated circuits”(2003).
2. Cheol Seong Hwang” (Ba,Sr)TiO3 thin films for ultra large scale dynamic
random access memory. A review on the process integration”.(1998)
3. S. Ezhilvalavan, Tseung-Yuen Tseng” Progress in the developments of
(Ba,Sr)TiO3 (BST) thin films for Gigabit era DRAMs”(2000).
4. G. D. Wilk, R. M. Wallaceb, J. M. Anthony” High- kgate dielectrics: Current
status and materials properties considerations”(2001).
5. Ofer Sneh*, Robert B.Clark-Phelps, Ana R.Londer gan, Jereld Winkler, Thomas
E.Seidel” Thin film atomic layer deposition equipment for semiconductor
processing”(2002).
6. E.P. Gusev , E. Cartier , D.A. Buchanan , M. Gribelyuk , M. Copel ,
a H. Okorn-Schmidt , C. D’Emic” Ultrathin high-K metal oxides on silicon:
processing, characterization and integration issues”(2001).
HIGH-K DIELECTRICS IN MICROELECTRONICS
References
7. D. E. Kotecki,J. D. Baniecki,H. Shen ,R. B. Laibowitz,K. L. Saenger ,J. J. Lian,T.
M Shaw ,S. D. Athavale,C. Cabral, Jr.,P. R. Duncombe ,M. Gutsche ,G. Kunkel ,Y.J. Park,Y.-Y. Wang,R. Wise “(Ba,Sr)TiO3 dielectrics for future stacked capacitor
DRAM”(1999).
8.Intel’s High Gate k/Metal Gate Announcement November 4th, 2003.
9.Wilman Tsai and Robert Chau” Integration of Metal gate-High k Dielectrics to
Extend Transistor Scaling”(2004).
HIGH-K DIELECTRICS IN MICROELECTRONICS