Nonvolatile
Memory
Technologies:
A Look into the
Future
Stefan Lai
Vice President, TMG, Intel Corporation
CoCo-Director, California Technology and
Manufacturing
February 2003
Key Messages
! Moore’s Law will continue through innovation
– Process complexity will increase to address
fundamental limits of physics
! To maintain Moore’s Law cost learning curve,
difficult to do it by transistor technology alone
– New opportunity for new memory structures and
new materials
! Current mainstream memory technologies of ETOX
and NAND will continue to be the key technologies
for more than 5 years out
! Intense research activities to identify scalable
memory technologies for 5 year and beyond
2
Agenda
! Moore’s Law will continue
! Emerging new memory technologies
! Market Potential for new memory
technologies
! Comparison of three memory
technologies
! Development Considerations
! Summary
3
Agenda
! Moore’s Law will continue
! Emerging new memory technologies
! Market Potential for new memory
technologies
! Comparison of three memory
technologies
! Development Considerations
! Summary
4
Moore’s Law will Continue with
ETOX Flash
! Currently shipping 8th generation of ETOX® flash
memory in high volume
– ~50% cell size reduction per generation
! Good visibility into 90 nm and 65 nm generation
! Current projection shows scaling continues at 45
nm node but challenged to meet 50% goal
! Further innovation required to maintain cost
learning curve
! Industry trend: complex transistor structure to
meet scaling challenges
5
ETOX® Technology Scaling
1986 / 1.5µ
µm
1996 / 0.4µ
µm
1988 / 1.0µ
µm
234 X
1998 / 0.25µ
µm
1991 / 0.8µ
µm
1993 / 0.6µ
µm
2000 / 0.18µ
µm
2002 / 0.13µ
µm
5.4X
Volume Production Year / Technology Generation
! 18 years and 8 Generations of ETOX® to 0.13 µm
6
Example of Future Transistor
Gate
Drain
Source
Silicon
Gate
Drain
Source
Source: Intel
Example of
Current Flash
Memory Cell
7
New Materials in Silicon
Technology
! The semiconductor industry has been addressing
the performance and cost issues by introducing
new materials
– Tantalum pentoxide for DRAM storage dielectric
– Cobalt and Nickel for S/D formation
– Copper and low k dielectric for interconnect
– High K dielectric for transistor gate
! For non-volatile memories, new memory materials
provide new opportunities for further memory cost
reduction
8
Agenda
! Moore’s Law will continue
! Emerging new memory technologies
! Market Potential for new memory
technologies
! Comparison of three memory
technologies
! Development Considerations
! Summary
9
NV Memory Mechanisms
Transistor Vt Shifts
1. Floating gate
2. Floating Trap
(nitride)
Charge
Displacement
1. Crystalline
Ferroelectric
2. Polymer
Ferroelectric
Resistance Change
1. Magnetic: GMR
or MJT
2. Phase Change
3. Complex metal
oxide
4. Polymer ionic
transport
10
Emerging Non-Volatile Memories
MRAM
Polymer
OUM
DataStorage
Storage Region
Data
Region
M4 Word Lines
Top View
Magnetic Storage Bits
Chalcogenide
Amorphous
Crystalline
Bit-Sense
Line
Sense Current
Directions
M3 Metal
1
M1 Word Lines
Side View
0
1
M2 Metal
M4 Word Lines
0
1
1
Phase
Phase Change
Change
Material
Interlayer
Dielectrics
Resistive
Electrode
Electrode
M1 Word Lines
FERAM
Heater
Heater
RRAM
FE Polymer
Word line
Word line
Polymer Layer
Bit line
Bit line
Bit line
Polymer Layer
Word line
* Other brands and names are the
property of their respective owners
11
What Is MRAM?
! Operation
– Cell is 1 MJT + 1 Transistor
– Electric current switches the
magnetic polarity
– Change in magnetic polarity
sensed as resistance
change
! Attributes
– Non-Volatile
– High Density
– Non Destructive Read
– Low Voltage & Low Power
– Write = Read Speed, < 50
nsec
– Unlimited R/W Endurance
– Material compatibility with
CMOS a key challenge
M4 Word Lines
Top View
Magnetic Storage Bits
Bit-Sense
Line
Sense Current
Directions
M3 Metal
1
M1 Word Lines
M4 Word Lines
Side View
0
1
0
1
M2 Metal
1
Interlayer
Dielectrics
M1 Word Lines
12
What Is FeRAM?
!
Operation
–
–
–
!
Selected PZT crystalline
materials have bi-stable
center atom
Data is stored by
applying an voltage to
polarize the internal
dipoles “Up” or “Down”
Non-Linear FRAM Read
Capacitor
Attributes
–
–
–
–
–
Non-Volatile
Larger Cell Size
“Fast” Random Read
Access
EApp
Fast Write with very low EFilm
power consumption
Destructive read,
limited read and write
cycles
Applied Electric Field
Moves Center Atom
Perovskite Crystal Unit Cell
PZT (PbO,ZrO2, TiO2) Lead-ZirconateTitanate
Tetra/Pentavalent Atom
Di/Monovalent Metal Atoms
Oxygen Atoms
Non- Linear FRAM Capacitor
Top Electrode
PZT Film Polarized
Bottom Electrode
ENet = EApp - EFilm
13
What Is OUM?
! Operation
Data Storage Region
! Chalcogenide
Poly Crystalline
Chalcogenide Amorphous
material alloys used
in re-writable CDs
Heater
and DVDs
Phase Change
Material
! Electrical energy
Resistive
Electrode
(heat) converts the
! Attributes
material between
– Non-volatile
crystalline
– High density
(conductive) and
– Non-destructive read
amorphous
– Low voltage and low power
(resistive) phases
– ~1012 write/erase cycles
– Easy to integrate w/ logic
! Cell reads by
measuring resistance
14
What Is RRAM?
! Operation
! PCMO material,
Complex metal oxide
studied for high temp
superconductivity
! Change in resistance
with applied electric field
! Low resistance with
forward bias, high
resistance when process
is reversed
! Low field read with no
charge disturb
Poly Crystalline
! Attributes
– Non-volatile
– High density
– Non-destructive read
– Low voltage and low
power
15
What Is Polymer Memory?
! Operation
! Polymer material with
special formulation
! Change in resistance
due to ionic transport
with applied electric field
! Low resistance when
ionic conductance paths
formed, high resistance
when process is
reversed when paths
broken
! Low field read with no
charge disturb
Poly Crystalline
! Attributes
– Non-volatile
– High density
– Non-destructive read
– Low voltage and low
power
– Low cost with polymer
16
What Is Ferroelectric Polymer Memory?
Word line
Word line
Polymer Layer
Bit line
Bit line
Bit line
Polymer Layer
Word line
Insulator (polymer)
Word line
Word line
Polymer Layer
Bit line
Bit line
Bit line
Polymer Layer
Word line
! Polymeric Ferroelectric RAM (PFRAM)
– Polymer chains with a dipole moment
– Data stored by changing the
polarization of the polymer between
metal lines
! Zero transistors per bit of storage
! Polymer layers can be stacked
! Memory is NON-Volatile
! Fast read and write speeds
– Microsecond initial reads
– Write speed comparable to flash
– Destructive read
Charge Pump
Sense Amps/
Interconnect Interface Logic
CMOS Base Wafer
dipole
moment
17
Agenda
! Moore’s Law will continue
! Emerging new memory technologies
! Market Potential for new memory
technologies
! Comparison of three memory
technologies
! Development Considerations
! Summary
18
Emerging Non-Volatile Memories
MRAM
Polymer
OUM
DataStorage
Storage Region
Data
Region
M4 Word Lines
Top View
Magnetic Storage Bits
Chalcogenide
Amorphous
Crystalline
Bit-Sense
Line
Sense Current
Directions
M3 Metal
1
M1 Word Lines
Side View
0
1
M2 Metal
M4 Word Lines
0
1
1
Phase
Phase Change
Change
Material
Interlayer
Dielectrics
Resistive
Electrode
Electrode
M1 Word Lines
FERAM
Heater
Heater
RRAM
FE Polymer
Word line
Word line
Polymer Layer
Bit line
Bit line
Bit line
Polymer Layer
Word line
* Other brands and names are the
property of their respective owners
19
Value of FE Polymer Memory
SemiConductor
Memories
Cost (expensive>)
SRAM
DRAM
Polymer
Memory
Disk Drives
Log Read/Write Time (faster>)
20
Value of FE Polymer Memory
! Given the relatively slow read and write time
(~50 µSec), FE polymer memory is not used
for execute in place applications (~100 nSec
required)
! Instead, it is best used in memory card
application where the slower read and write
time as well as the 108 cycle capability are
adequate
! The multi-layer capability can provide very
low cost memory systems in portable
handheld systems
21
Emerging Non-Volatile Memories
MRAM
Polymer
OUM
DataStorage
Storage Region
Data
Region
M4 Word Lines
Top View
Magnetic Storage Bits
Chalcogenide
Amorphous
Crystalline
Bit-Sense
Line
Sense Current
Directions
M3 Metal
1
M1 Word Lines
Side View
0
1
M2 Metal
M4 Word Lines
0
1
1
Phase
Phase Change
Change
Material
Interlayer
Dielectrics
Resistive
Electrode
Electrode
M1 Word Lines
FERAM
Heater
Heater
RRAM
FE Polymer
Word line
Word line
Polymer Layer
Bit line
Bit line
Bit line
Polymer Layer
Word line
* Other brands and names are the
property of their respective owners
22
Value of New NV RAM
Volatile
Memory
Space
Log Write Time (faster >)
New NV RAM Space
FeRAM OUM MRAM
Limited
Unlimited Read
Read Cycles
Cycles
SRAM
DRAM
Flash Space
ETOX
NAND
ROM Space
Unlimited Read Cycles
ROM
EPROM
Not in-system
Changeable
Unlimited Read
Cycles
Log Number of Erase/Write Cycles
23
Value of New NV RAM
! Increase in functionality increases market value
! SRAM/DRAMs have fast read/write times and
unlimited number of cycles, but they require power
to maintain memory
! Flash is non-volatile but is slow to write and limited
number of write/erase cycles (1 million)
! A memory that is fast write and capable of high
number of write/erase cycles is of high value to low
power portable applications
– Low power is more important than performance:
non volatility key
– Limited cellular bandwidth limits cycle
requirement
24
Agenda
! Moore’s Law will continue
! Emerging new memory technologies
! Market Potential for new memory
technologies
! Comparison of three memory
technologies
! Development Considerations
! Summary
25
Emerging Non-Volatile Memories
MRAM
Ion Polymer
OUM
DataStorage
Storage Region
Data
Region
M4 Word Lines
Top View
Magnetic Storage Bits
Chalcogenide
Amorphous
Crystalline
Bit-Sense
Line
Sense Current
Directions
M3 Metal
1
M1 Word Lines
Side View
0
1
M2 Metal
M4 Word Lines
0
1
1
Phase
Phase Change
Change
Material
Interlayer
Dielectrics
Resistive
Electrode
Electrode
M1 Word Lines
FERAM
Heater
Heater
RRAM
FE Polymer
Word line
Word line
Polymer Layer
Bit line
Bit line
Bit line
Polymer Layer
Word line
* Other brands and names are the
property of their respective owners
26
Technology Comparison
MRAM
Fastest Read and
Write, Unlimited
Cycles
FeRAM
OUM
Fast Read and Write, Fast Read and Write,
1012 cycles
1012 cycles
High Current/Power
Lowest
Current/Power
High Current/Power
Non Destructive
Read
Destructive Read
Non Destructive
Read
Special Process
Special Process
“Bolt on” Process
Larger Cell Size
Larger Cell Size
Smaller Cell Size
27
Agenda
! Moore’s Law will continue
! Emerging new memory technologies
! Market Potential for new memory
technologies
! Comparison of three memory
technologies
! Development Considerations
! Summary
28
Unique Challenges of Non-Volatile
Memories
! Commonly accepted NV memory retention time spec
is 10 years
! Retention is NEVER limited by the typical bits: it is
always limited by defect mechanisms
! Fundamentally, storage mechanisms with fast write
may have too low an energy barrier for long term
stable retention
! In most cases, the write mechanism may cause
degradation to either the write mechanism itself or
to retention: giving limited cycling capability
29
Circuit Consideration
! All the new memory elements are two terminal
devices, acting either as a resistor or a capacitor
– Different from ETOX® flash, which is a 3 terminal
transistor
– Array architecture important to minimize cross
cell disturb
! Ferroelectric devices senses displacement charge
from change in polarization: similar to DRAM, low
current, but limit to minimum cell capacitance
! MRAM requires sensing of very small change in
resistance, most stringent of the new memories
! Resistance change memories all require higher
level of switch current from the X-decoder in tight
pitch
30
Manufacturing Consideration
! All the new memories discussed involves
new materials that may not be compatible
with standard silicon process and may
require new manufacturing processes and
new equipment
! Advanced lithography is still required:
advancement in lithography including
optical enhancement technologies are
important for low cost
! With new memory mechanism, new testing
methods as well as new testers may be
required
31
Agenda
! Moore’s Law will continue
! Emerging new memory technologies
! Market Potential for new memory
technologies
! Comparison of three memory
technologies
! Development Considerations
! Summary
32
Summary
! Moore’s Law will continue through innovation
– Process complexity will increase to address
fundamental limits of physics
! To maintain Moore’s Law cost learning curve,
difficult to do it by transistor technology alone
– New opportunity for new memory structures and
new materials
! Current mainstream memory technologies of ETOX
and NAND will continue to be the key technologies
for more than 5 years out
! Intense research activities to identify scalable
memory technologies for 5 year and beyond
33