Resistive RAM, present status and future applications

Christophe Chevallier

Workshop on Data-Abundant System Technology April 22-23, 2014

© 2014 Christophe Chevallier1

What is Resistive RAM?

Comparison to other emerging technology

Comparison to existing technologies

Applications

Development status

© 2014 Christophe Chevallier 2

Stack

Model

Properties

© 2014 Christophe Chevallier

Bottom E.

MetalOxide

Top Electrode

Bottom E.

MetalOxide

Top Electrode

Initial Structure “Formed” Structure

Programmed Erased

read

Bottom E.

MetalOxide

Top Electrode

Bottom E.

MetalOxide

Top Electrode

3

1D –1R1T –1R

2 terminal device

◦ Can be stacked for density

Known materials

◦ Ease of Fab integration

BEOL – Back End Of Line fabrication

◦ No impact on existing standard cell

libraries

◦ Easier integration

Bit writable – bit erasable

◦ Faster system through-put

Low Voltage operation low power


Bottom E.

MetalOxide

Top Electrode

L0

L1

L2

L3

4

Many structures and

materials

The most studied

approach is ReRAM,

with binary oxide

Cell type: ReRAM CBRAM Tunnel RRAM

principle filament filamentInterfacial switching

Write / read current

high High Low

Forming yes yes no

Voltage ~3.5V 1V ~2.5V

materialsBinary Oxide

Ag, Cu Filament

in electrolyte

Perovskite + tunnel oxide

reliability Better data retentionmedium

data retention

Best applications

Embedded / fastaccess

Ultra Low power

High density

Who wins? It depends on the

application


45nm node PCM(Phase Change)

STT-MRAM(Spin Torque Transfer)

RRAM(Resistive / Redox)

CNT RAM(Carbon Nanotube)

Materials

Write Energy 4 pJ 1 pJ 1 pJ <1 pJ

Write Time 10 ns 5 ns 10 ns 3 ns

Endurance 108 1010 106 1012

Retention 10 yrs, 85oC 10 yrs, 85oC 10 yrs, 85oC 1000 yrs, 85oC

Production

status

Gb level 64 Mb 1 Mb,Limited production

One source only,

Not in production

RRAM: fab-friendly materials, and good specs – a lot of developments © 2014 Christophe Chevallier

electrode

CNT mesh

electrode

6




Applications◦ Impact on storage appliance

Development status


L1, SRAM

Archive: Tape, Non Volatile, s

Flash:Non-Volatile, μs

DRAMVolatile, 10s ns

L2/L3 Cache, ns

Disk:Non-Volatile, ms

DRAMVolatile, 10s ns

Archive: Tape, Disk

L1SRAM

Storage Class Memory: Non-Volatile, 10s ns

L2/L3 Cache, ns


Latency

density

Cost/bit

RRAM could replace DRAM and Flash. RRAM could provide a fast latency ( < 1 us), high density solution.

application EmbeddeduC code, exec.NOR-like

RAM-likeCached data

NAND-likestorage

FPGA Logic (D-FlipFlopreplacement)

Best in class e-Flash, OTP fuses

DRAM, PCM, MRAM?

NAND SRAM (MRAM)

Read access < 50 ns < 20ns 25 us latency

ns ns

Endurancerequirement

10 typ. / 104 106 to 108 104 100 1012

Data retention

10 years at 85C/125C

30 days at 55C

1 year at 70C

10 years at 85C

Seconds to years

RRAM today? Difficult for the automotive spec

Stretchesendurance, possible

Yield of large density chip unproven, possible

Possible Endurance is too low, Algorithm hard to implement


Cache replacement

8MB of MRAM hard drive

cache

Fast read and write access

Buffalo SSD (MRAM / NAND)

Skyera / Everspin

Techon 5/21/2012

RRAM advantage: small cell sizeFast write speedLower power (NVM, no refresh)


NAND

RRAM,PCM,MRAM

• USB key, cards– Endurance: 100 typ.

– Data Retention: months, at 70C

– Temperature: room

– Reliability: low

• Mobile Storage (phones, tablets) Endurance: 104

Data Retention: months at 85C

• SSD Endurance: 104

– Data Retention: years at 85C

– Temperature: 0 -70C

– Reliability: high

• Data Center• DRAM / Drive replacement

• Cache for hard drives

– Endurance: high

– Data Retention: days at 55C

– Temperature: controlled

– Reliability: high

– Fast power-up

PerformanceReliability

Low Cost

RRAM advantage: • endurance• fast write speed • byte erasable• low power


Comparing ReRAM to NAND.

Technological Basis for advantages

Power: Low Voltage, small arrays (low C)

Speed (latency): small array (low RC)

Cost: lower mask count (no HV devices, no Floating

Gate)

Endurance / Retention: “more electrons”, different

technology. Not proven in high density or compared to

3D-NAND


NAND RRAM

3D

NANDRRAM




Applications◦ Impact on storage appliance

Development status



Bottom E.

MetalOxide

Top Electrode

Many levels of development:

Cell Chip SSD Storage Applicance Data Center Cloud /internet user

14

Function of an SSD controller

Read and write caching

Error-correcting code (ECC)

handling

Bad block mapping

Wear leveling

Read disturb management

Garbage collection

Encryption

Compression


ReRAM advantages

small block, low latency

Same or worse (for now)

Much simpler

Still needed but better

Better or not needed

Much less frequent

Similar

Similar

15

Resistive RAM will greatly simplify memory management and improve system speed

Function of a data

center:

Persistence - ACID

transactions

De-duplication, …

Operations: search,

social media vs.

compute intensive

apps


Resistive RAM will speed up processing with lower latency, faster random access operations. The proper architecture needs to be designed in.

Jichuang Chang, HP labs


Power advantage: low

energy datapaths, co-

location of computing

and data storage

Strukov, PNAS 2009 ReRAM can be stacked up above and near the logic circuitry

Nano-Stores at HP-Labs

17

F. Alibart, CNRS, Lille, France© 2014 Christophe Chevallier

The crosspoint array is perfectly suited to massive parallel processing. Each ReRAM cell can be programmed to an analog weight.

18




Applications

Development status


ISSCC 2012 -14 / IEDM 2011

NAND 128 Gb, in high volume production

PCM 8 Gb, small volume production

MRAM 64Mb, in production

RRAM 16Gb/32Gb test chips, 8Mb in pre-

production

16nm 128 Gb NAND

180 nm RRAM 8Mb macro

65 nm 64Mb MRAM

20nm 8Gb PCM

24nm, 32Gb RRAM (test chip)

27nm, 16Gb CBRAM(test chip)


Embedded code and parameters storage◦ Existing implementations

Cache (1T - 1R)◦ Will replace DRAM, displace MRAM, PCM with lower

power, simpler fabrication

High Density (1D – 1R)◦ Will displace NAND with low latency, higher endurance,

and byte-level operations


KB densitySensors(90 – 130 nm)

MB densityCache(40 – 130nm)

GB densityNAND displacement(20 – 45 nm)

2013

21

Resistive RAM can bring:

Low latency, low power and high density

Fast system speed – byte operability

Higher reliability than NAND Flash

With new data processing demands, new

architectures are required. Resistive RAM can

enable these architectures.


Resistive RAM will displace NAND, not replace it. It will enable architectures optimized for data-focused applications.

Documents

Resistive RAM, present status and future applications