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Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Memristor Materials Engineering: From Flash Replacement Towards a Universal Memory
Janice Nickel Hewlett Packard Laboratories, nanoElectronic Research Group IEDM Advanced Memory Technology Workshop 4 December 2011
2 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
HP Confidential and Restricted Distribution Internal Use Only.
Outline
Memory and HP
Introduction to memristors
Challenges facing realization of memristor memory
Engineering solutions
CMOS compatible fabricated memristors
Alternate Emerging Memories comparison
The Team
Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Why memory? Whats in it for HP?
4 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Reliable supply of scalable memory technology HPs needs
FLASH scalability is approaching its limit Control of charge placement deteriorates with reduced oxide thickness Multi-level cells have low realistic endurance Relying on Through Silicon Vias to increase capacity
DRAM is fast approaching theirs Control of trench widths deteriorates with depth DRAM architectures and circuitry are adapted to 25 fF cell capacitance Shrinking geometries threaten industry ability to maintain 25fF
Taller cell capacitor / Thinner cell dielectric
5 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Considerations Replacement Technology
CMOS compatibility
Speed
Yield
Die Size
Materials
Cell size
Access Device
Endurance
Retention
Device non-linearity
Operating Temperature
Forming
Bandwidth
Latency
Energy
Non-volatility
Cost
Fabrication Performance
Idle Power
6 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Considerations Replacement Technology
CMOS compatibility
Speed
Yield
Die Size
Materials
Cell size
Access Device
Endurance
Retention
Device non-linearity
Operating Temperature
Forming
Bandwidth
Latency
Energy
Non-volatility
Cost
Utilize current infrastructure
Compatible w/ Si technology
>95 % per mask
Limits scalability
10 Years
95*C Idle
Power
7 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Considerations Replacement Technology
CMOS compatibility
Speed
Idle Power
Yield
Die Size
Materials
Cell size
Access Device
Endurance
Retention
Device non-linearity
Operating Temperature
Forming
Bandwidth
Latency
Energy
Non-volatility
Cost
FLASH
Yes
R: 25 ms W: 200ms
< 20-50 s
$1/Gbyte
Yes ~ 105 cycles
> 25 Mb/s
10,000 pJ/op
1 mW/Gb
4-6 F2
64 Gbit
Burn in
years
8 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Enables true crossbar structures Why are memristors candidate replacements?
Does not require transistors or other access devices
Removes Silicon requirement Stack arrays on top of each other: cell sizes < 4F2
Improve density Reduce power consumption Integrate with compute processors Reduce total area
P Pitch = 2F for cross bars
F Feature size = Litho node
Cell Size = 4 F2
9 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
TIME
HP memristor opportunities
CHIP DEVELOPMENT
FLASH REPLACEMENT
DRAM REPLACEMENT
UNIVERSAL MEMORY
NEURAL COMPUTING
WE ARE HERE
SOLID STATE DISK
Memristor
Floppy Disk
Optical disk
Hard Disk
Flash
RAM
Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Introduction What is a Memristor?
11 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
MEMRISTOR d = M dq
1971 Chua
Fourth Fundamental Two Terminal Circuit Element The Memristor: Predicted
v q i
Ohm 1827
1831 Faraday
Von Kleist 1745
Leon Chua U.C. Berkeley
RESISTOR dv = R di
CAPACITOR dq = C dv
INDUCTOR d = L di
i
v
q
d/dt = v dq /dt = i
12 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Dynamical Non-Linear Behavior The Memristor: Fundamentally Different
iiwMv ),(=
( , )dw f w idt
=
Generalized Memristor (Memristive system):
L. Chua and S. M. Kang, Proceedings of the IEEE, Vol. 64, No. 2, February 1976
13 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Reduced to Practice in 2008 The Memristor: Found
R. Stanley Williams HP Laboratories
D. B. Strukov, et al., vol 453, 1 May 2008, doi:10.1038/nature06932
14 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Inability to duplicate properties with the other passive circuit elements What makes a memristor fundamental?
14
VOLT
AG
E
CU
RREN
T
VOLTAGE
RESISTOR
dv = R di
CAPACITOR
dq = C dv
INDUCTOR
d = L di
MEMRISTOR
d = M dq
CU
RREN
T C
URR
ENT
VOLTAGE
15 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Cross-bar device with multivalent oxide What exactly is it?
..
Top Electrode (TE)
Switching Layer Multi-Valent Oxide
Bottom Electrode (BE)
Nano-devices 1x17 BE
TE
oxide
16 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
TiO2
Semiconducting Bipolar Switch How does it work?
Previously: Fixed semiconductor structure and only electronic motion Now: Ionic motion dynamically modulates the semiconductor structure controlling the electronic current.
Under positive bias voltage: O vacancies drift to the BE Narrows the tunneling gap Reduces resistance.
+
Under negative bias voltage: O vacancies to drift to the TE Increases tunneling gap Increases resistance
Oxygen Vacancies
highly resistive TiO2 region a conductive TiO2-x region
contains positively charged O+ vacancies
specific electrodes
Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Memristor Challenges and Solutions Controlling the system through device engineering
18 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Considerations Replacement Technology
CMOS compatibility
Speed
Power
Yield
Array Size
Materials
Cell size
Access Device
Endurance
Retention
Device non-linearity
Operating Temperature
Forming
Bandwidth
Latency
Energy
Non-volatility
Cost
Forming
19 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Creating Oxygen Vacancies Electroforming
Vacancies formed by: rip O2 from TiO2 evolve O2 gas
+ V on TE
Bubbles appear with application of +V
+ V removed
Bubbles disappeared immediately when the +V is removed
Some small permanent deformations remain
O2- O2 O2- O2-
-V TiO2
+V
forming 1st ON switching 1st OFF switching
0.2
0.1
0
0.1
Cur
rent
(mA
)
Device Voltage (V)
TiO2
Pt
Pt
O2 gas disappears as voltage is removed
Physical Damage occurs when Creating Vacancies
by Electroforming
20 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Physical Mechanism Electroforming
Rings show known Pt and Anatase polycrystalline diffraction
Remaining diffraction peaks correspond to Ti4O7 Magneli phase,
Room temperature metallic suboxide of TiO2!!
Ti4O7 diffraction
J.P. Strachan et al., Advanced Materials, Volume: 22, Issue: 32, Pages: 3573-3577
21 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Experimental Observation of Magneli Phase
-D. H. Kwon et. al, Nature Nanotechnology, 17 Jan 2010
Electroforming
22 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
4nm TiO2/35 nm Ti4O7
Eliminating electroforming Engineer Vacancy Reservoir into Device
1st ON switching Forming
1st OFF switching C
urre
nt (m
A)
Device Voltage (V)
1.5
1
0.5
1.5
0.5
0
1
0 1.0 0.5 0.5 1
Pt
TiO2 Ti4O7
Pt
23 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Pt
TiO2 Ti4O7
AFM images before and after forming Eliminating electroforming
forming
TiO2
Pt
Pt
forming
Pt
24 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Year
2008 2009 2010 2011 2012
Endu
ranc
e (c
ycle
s)
103104105106107108109101010111012101310141015
A History Endurance
TiO2
Pt
Pt
Requires electro-forming
Nanotechnology 22 (2011) 254026
25 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Year
2008 2009 2010 2011 2012
Endu
ranc
e (c
ycle
s)
103104105106107108109101010111012101310141015
A History Endurance
No electro-forming Unstable states
Appl. Phys. Lett. 97, 232102 (2010)
Pt
TiO2 Ti4O7
Pt
26 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Year
2008 2009 2010 2011 2012
Endu
ranc
e (c
ycle
s)
103104105106107108109101010111012101310141015
A History Endurance
TaOx
Pt
Pt
Requires electro-forming
27 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Year
2008 2009 2010 2011 2012
Endu
ranc
e (c
ycle
s)
103104105106107108109101010111012101310141015
A History Endurance
No electro-forming Stable states
Ta2O5
Ta
Pt
Appl. Phys. Lett. 97, 232102 (2010);
28 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Year
2008 2009 2010 2011 2012
Endu
ranc
e (c
ycle
s)
103104105106107108109101010111012101310141015
A History Endurance
No electro-forming Stable states
Pt
Pt
Ta2O5-x TaO2
HP Labs results
Myong-Jae Lee et al., nature materials, doi:10.1038
SAIT results
29 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
A Future Endurance
Year
2008 2009 2010 2011 2012
Endu
ranc
e (c
ycle
s)
103104105106107108109101010111012101310141015
SAIT results
HP Labs results
DRAM consumer replacement
30 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
An Understanding Endurance
Ta2O5
Ta
Pt
100 101 102 103 104 105 106102
103
104 Ti 1nm /Pt 100nm/TiOx 29nm/Ti4O7 100nm
Resis
tance
(ohm
)
switching cycles
Ron Roff
a)
100 101 102 103 104 105 106102
103
104 Ti 1nm /Pt 100nm/TiOx 29nm/Ti4O7 100nm
Resis
tance
(ohm
)
switching cycles
Ron Roff
a)
No electro-forming Unstable states
2.0x109 4.0x109 6.0x109 8.0x109 1.0x1010 1.2x1010102
103
Resi
stan
ce (o
hm)
switching cycles
Ron Roff
No electro-forming Stable states
Pt
TiO2 Ti4O7
Pt
31 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
An Understanding Endurance
-4 -3 -2 -1 0 1 2 3102
103
104
105
106
Resis
tance
(Ohm
)
Voltage (V)
TiOx
-4 -3 -2 -1 0 1 2 3102
103
104
105
106
Resis
tance
(Ohm
)
Voltage (V)
TiOx
-4 -3 -2 -1 0 1 2 3
102
103
104
Resis
tance
(Ohm
)
Voltage (V)
TaOx)
-4 -3 -2 -1 0 1 2 3
102
103
104
Resis
tance
(Ohm
)
Voltage (V)
TaOx)
Ta2O5
Ta
Pt Pt
TiO2 Ti4O7
Pt
No electro-forming Unstable states
No electro-forming Stable states
32 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Pt
TiO2 Ti4O7
Pt
An Understanding Endurance
100 101 102 103 104 105 106102
103
104 Ti 1nm /Pt 100nm/TiOx 29nm/Ti4O7 100nmRe
sistan
ce (oh
m)
switching cycles
Ron Roff
a)
100 101 102 103 104 105 106102
103
104 Ti 1nm /Pt 100nm/TiOx 29nm/Ti4O7 100nmRe
sistan
ce (oh
m)
switching cycles
Ron Roff
a)
TinO2n-1 channel multiple states
-4 -3 -2 -1 0 1 2 3102
103
104
105
106
Resis
tance
(Ohm
)
Voltage (V)
TiOx
-4 -3 -2 -1 0 1 2 3102
103
104
105
106
Resis
tance
(Ohm
)
Voltage (V)
TiOx
TiO2 Ti
Magnelli Phases
33 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
An Understanding Endurance
-4 -3 -2 -1 0 1 2 3
102
103
104
Resis
tance
(Ohm
)
Voltage (V)
TaOx)
-4 -3 -2 -1 0 1 2 3
102
103
104
Resis
tance
(Ohm
)
Voltage (V)
TaOx)
Ta2O5
Ta
Pt
g y
100 101 102 103 104 105 106 107 108 109102
103Ti 1nm /Pt 100nm/TaOx 12nm/Ta 100nm
switching cycles
Resis
tance
(ohm
)
Ron Roff
b)
g y
100 101 102 103 104 105 106 107 108 109102
103Ti 1nm /Pt 100nm/TaOx 12nm/Ta 100nm
switching cycles
Resis
tance
(ohm
)
Ron Roff
b)
Ta (O) channel in equilibrium
34 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Materials and Device Engineering
Requires large voltages not compatible w/ CMOS Physically damages devices Results in low yield Reduces the endurance of the device Improved by systematic understanding of the system Moores law improvement in endurance ~102.5 /year Fast approaching endurance usable for consumer DRAM
replacement Understanding of materials properties and physical
mechanisms essential to improving device properties
Electroforming
Endurance
Understanding Mechanisms Results in Device Improvements
35 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Considerations Replacement Technology
CMOS compatibility
Speed
Power
Yield
Array Size
Materials
Cell size
Access Device
Endurance
Retention
Device non-linearity
Operating Temperature
Forming
Bandwidth
Latency
Energy
Non-volatility
Cost
36 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Device Non-Linearity
Pt TaOx Ti4O7
Ta2O5
Ta
Pt
Pt 35nm /Ti4O7/4 nm TaOx /Pt
Pt 100 nm /12 nm TaOx /Ta 100 nm
Cur
rent
(mA
) C
urre
nt (m
A)
-1
-1
1
1
0
0 -0.8 -0.4 0.4
--0.4
0.4
0
--0.8
Voltage (V) 0
Voltage (V)
ON
OFF
Ta
37 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Current Sneak Paths Cross bar challenges
Half Select Problem
38 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Current Sneak Paths Cross bar challenges
+ 0 or 1 threshold
V
Sense amps
39 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Current Sneak Paths Cross bar challenges
+ 0 or 1 threshold
V
Sense amps
40 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Current Sneak Paths Cross bar challenges
+ 0 or 1 threshold
V
Sense amps
41 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Current Sneak Paths Cross bar challenges
+ 0 or 1 threshold
V
Sense amps
42 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Current Sneak Paths Cross bar challenges
+ 0 or 1 threshold
Sense amps
V
= +
Cur
rent
Voltage
ON
OFF
43 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Current Sneak Paths Cross bar challenges
+ 0 or 1 threshold
Sense amps
V
= +
Cur
rent
Voltage
ON
OFF
44 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Materials and Device Engineering
Negate the need for an access device Reduce current requirement Increase the possible array size Enable integration of memristors with processors Enable increased density by stacking layers
Device Nonlinearity
Understanding Mechanisms Results in Device Improvements
Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
CMOS compatible fabricated memristors 300 mm wafer fabrication at 130 nm node
46 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Fabrication Friendly Materials and Processes CMOS compatibility
M2
M1
Bit Via
Reset 0.5
0.0
-0.5 Cur
rent
(mA
)
-0.8 -0.4 0.0 0.4 Device Voltage (V)
Set
1ST 300 mm wafer produced by HP Utilizes industry standard processes and materials
Independently defined working memristor bits
TiN
TiO2 Ti4O7
TiN
Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Memristor vs. Other Emerging Technologies
48 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Dynamical and Non-Linear Enables True Cross-point How does it stand up as a memory?
Memristor PCM STTRAM DRAM Flash HDD
Density (F2) 4 816 1464 610 46 2/3
Energy per bit (pJ) 0.13 227 0.1 2 10000 110x109
Read time (ns)
49 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Meets or Beats FLASH on all fronts Memristor as a Candidate FLASH replacement
CMOS compatibility
Speed
Idle Power
Yield
Size
Materials
Cell size
Access Device
Endurance
Retention
Device non-linearity
Forming
Bandwidth
Latency
Energy
Non-volatility
Cost
FLASH
Operating Temperature
50 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
TIME
HP memristor opportunities
CHIP DEVELOPMENT
FLASH REPLACEMENT
DRAM REPLACEMENT
UNIVERSAL MEMORY
NEURAL COMPUTING
WE ARE HERE
SOLID STATE DISK
Memristor
Floppy Disk
Optical disk
Hard Disk
Flash
RAM
Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
The Team
52 Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
nanoElectronics Research Group
Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Thank you
Copyright 2011 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice.
Questions?
2011 IEDM Short Course Main MenuIntroduction and OverviewDRAM Technology - History & ChallengesManaging Challenges on Reliability and Applications from NAND Flash ScalingRedox-Based Resistive Switching Memories The Mystery of Nanoionic ProcessesMemristor Materials Engineering: From Flash Replacement towards a Universal MemoryThe Phase Change Run to Nonvolatile Storage at the NanoscaleEmerging Magnetic Memory Technologies
