SIDP Semiconductor Integrated

Device & Process laboratory

RRAM based analog synapse device

for neuromorphic system

Kibong Moon, Euijun Cha, and Hyunsang Hwang

The 13th Korea-U.S. Forum on Nanotechnology, Sep. 26-27, Seoul, Korea

Pohang University of Science and Technology (POSTECH), Korea

SIDP Semiconductor Integrated

Device & Process laboratory

Outline

• Introduction and Motivation

• Mo/PCMO synapse device

• Pattern recalling system

• Summary

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Introduction

Source: HP Neuron (~1011) + Synapse (~1015) + Learning Rule

Low energy (~10fJ) synapse and neuron devices

SIDP Semiconductor Integrated

Device & Process laboratory

Introduction Stanford Univ., IEDM 2013 CEA-LETI, IEDM 2012

Various new synapse devices were proposed (CBRAM, PCM, 3T-

FeMEM, and RRAM)

Univ. of Nat. Chiao Tung, IEDM 2014 Panasonic, VLSI 2013

SIDP Semiconductor Integrated

Device & Process laboratory

Introduction CEA-LETI, NEWCAS 2011 IBM, TED 2013

Problems : Large device area, power consumption, circuit

complexity etc..

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Device & Process laboratory

Introduction Carnegie Mellon Univ., VLSI 2015 Pennsylvania Univ., IEDM 2014

VO2 Insulator-Metal-Transition temperature ~ 67°C

: Not practical for device application

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Device & Process laboratory

Mo/PCMO synapse device

-4 -2 0 2

10-11

10-9

10-7

10-5

10-1

101

103

10-9

10-7

10-5

10-3

Mo/PCMO

Cu

rren

t [A

]

Voltage [V]

Cycles

1st

100thILRS

@ -0.5V

Cu

rren

t [A

]Active area [㎛2]

O2- O2-

VReRAM < 0V

<SET>

PCMO

B. E.

O2- O2-

VReRAM > 0V

<RESET>

Mo

MoOx

PCMO

B. E.

Mo

MoOx

Current level ∝ Active area

Field-induce oxygen migration & redox reaction at the interface

: Control thickness of interface oxide and device resistivity

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Device & Process laboratory

Mo/PCMO synapse device

4nm 4nm

PCMO PCMO

Mo Mo

~2.3nm ~4.2nm

LRS HRS

MoOx MoOx

11k-bit array

Well fabricated without mixing

(Mo/PCMO)

Direct evidence of redox

reaction at the interface

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Device & Process laboratory

Mo/PCMO synapse device

0 200 400 600 800 1000

0

2n

4n

6n

8n

10n

0 200 400 600 800 1000

5n

10n

15n

20n

25n

Vbias

(1ms) =

1V

1.5V

2V

2.5V

PotentiationV

bias (1ms) =

-2.5V

-3V

-3.5V

-4V

Depression

Cu

rren

t [A

]# of pulses

Vread

= -0.5V

Cu

rren

t [A

]

-3 -2 -1 0

0.0μ

0.3μ

0.6μ

0.9μ

1.2μ

0 1 2 3

0.5μ

0.4μ

0.3μ

0.2μ

0.1μ

0.0μ

Cu

rren

t [A

]

Voltage [V]

Reset

Set

1st

2nd

3rd

4th

5th

Cu

rren

t [A

]

Voltage [V]

Potentiation (-V)

: Increase conductance

: Strengthen synaptic weight

DC property AC property

Depression (+V)

: Decrease conductance

: Weaken synaptic weight

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NbO2 neuron device

0.4 0.8 1.2

0

2m

4m

6m

Roff

(~15㏀)

Ron

(~1.9㏀)

800us

Time

Voltage

1.5V

NbO2

AC I-V

Cu

rre

nt

[A]

Voltage [V]

0

1

0

1

0

1

0 1 2 3 4 5

0

50

Vin

I ou

t [m

A]

Vin

I ou

t [u

A]

Time [us]

Super-threshold input ∆V=1.6V

Sub-threshold input ∆V=0.9V

Neuron Synapse Input Output

NbO2 based oscillation characteristics with synapse device

Above critical threshold voltage Oscillation behavior

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Pattern recalling system

V1 V42

~

~

~

~

I1

I42

Upper threshold

Lower threshold

Noisy

input

…

Output

~ ~ ~ ~

SEM image Operation of Hopfield network on 11k-bit array

Packaging Standard

Pattern

Neuromorphic application using 11k-bit array Mo/PCMO synapse

device and NbO2 IMT oscillator neuron devices

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Pattern recalling system

Synapse weight mapping : Binary and Analog synapse based Hop-

field neural network

Analog synapse shows much better pattern recognition accuracy

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Device & Process laboratory

Summary

Mo/PCMO analog synapse device

- Field-induced oxygen migration for switching of Mo/PCMO device

- Fabrication of large scale synapse array device on 8-inch wafer

- Evaluating synapse characteristics for an artificial synapse

Hardware implmenetation of neuromorphic application

- NbO2 oscillator as an artificial neuron

- Integrating Mo/PCMO synapse array and NbO2 neuron

- Improved pattern recalling accuracy using analog synapse

SIDP Semiconductor Integrated

Device & Process laboratory

This research was supported by the Pioneer Research Center Program through

the National Research Foundation of Korea funded by the Ministry of Science,

ICT & Future Planning (2012-0009460)

Thank you for your

attention…!