30 nm © 2005 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice Atomic Switch ITRS Emerging.

30 nm

© 2005 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice

Atomic SwitchITRS

Emerging Research Devices

Philip Kuekes Hewlett-Packard Labs

2

Ionic and electronic switching • thermal, electrical or ion-migration-induced

switching mechanisms• Nanoionics-based resistive switching

memories

Rainer Waser & Masakazu Aono

Nat Mater. 2007 Nov ;6 (11):833-40

3

Ionic and electronic switching

• cation-migration • electrochemical growth and dissolution of

metallic filaments

4

Ionic and electronic switching

• anion-migration • transition metal oxides• electronically conducting paths of sub-

oxides• Schottky barrier

5

Pt PtTiO2 TiO2-x

3 nm

2 n

mIonic and electronic switching

We used to think about fixed semiconductor structure and only electronic motion.

Now we have ionic motion that dynamically modulates the semiconductor structure that controls the electronic current.

Diodes needed in ON state!

6

1. Nano-device switching is due to TiOx

2. TiOx switching is controlled by oxygen vacancy distribution- TiOx is a semiconductor doped by oxygen vacancies- charged oxygen vacancies drift under high field- deliberate placement of oxygen vacancies can engineer the switching- electroforming is a critical device step

3. Dynamic theory of oxygen vacancy drift fits experiment- oxygen vacancy distribution controls electron conductivity- vacancy drift modulates junction conductance- fundamental memristor theory matches experiment- detailed dynamics are highly nonlinear

4. New circuits enabled by these nano-switches- NVRAM- adaptive signal conditioning- adaptive intelligent machines

Metal/TiOx/Metal Device Physics

7

50 nanometer Pt/TiOx/Pt devices

-200

-100

0

100

200

Cur

rent

( u

A )

-2 -1 0 1 2Voltage ( V )

4

2

0Cur

rent

( n

A )

-2 -1 0 1 2Voltage ( V )

a

b

Virgin I-V

c

50 nm hp

+V pushOV vacancies

-V attractOV vacancies

10-3

10-6

10-9

-1 0 1

Pt

Pt

TiO2

TiOxV+

-

Switching I-V

TiOx

Pt

TiO2

Pt

page 8

< 50 nanosecond Pt/TiOx/Pt devices

-15

-10

-5

0

5

10

15

Curre

nt (1

0-3

A)

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0Junction Voltage (V)

t = 36 ns

t = 1 us

9

What is TiO2-x ?2 – TiOx controlled by oxygen vacancies

rutile TiO2

3.0/3.2 eV semiconductor

TiO2-x : x ~ 10-3 – 10-2

dopants all ionized Ei < 0.1 eV

oxygen vacancies VO2+ @ low T < 800C & high P(O2)

and Ti interstitials Tii4+ @ high T > 1000C & low P(O2):

creation ~ 3-5 eVdiffusion ~ 0.7 - 1.1 eVmobility ~ 10-10 – 10-14 cm2/Vs

10

Voltage (V)Voltage (V)

Vacancies control electrical symmetry!

30

20

10

x10-9

-1.0 -0.5 0.0 0.5 1.0

15

10

5

0

-5

x10

-3

-2.0 -1.0 0.0 1.0

I

Cu

rre

nt

(nA

)C

urr

en

t (m

A) I’

b

a

-30

-25

-20

-15

-10

-5

0

x10-9

1.00.50.0-0.5-1.0

-20

-10

0

10

x10

-3

2.01.00.0-1.0

IIC

urr

en

t (n

A)

Cu

rre

nt

(mA

) II’

e

d

TiOx

Pt

TiO2

Pt

TiO2

Pt

TiOx

Pt

7 n

m7

nm

11

-1.0

-0.5

0.0

0.5

1.0

x10

-3

1.00.50.0-0.5-1.0

15

10

5

0

-5

x10

-3

-2.0 -1.0 0.0 1.0-20

-10

0

10

x10

-3

2.01.00.0-1.0

-60

-40

-20

0

x10-6

-1.0 -0.5 0.0 0.5 1.0

Vacancies control electrical symmetry!

30

20

10

x10-9

-1.0 -0.5 0.0 0.5 1.0

I

Cu

rre

nt

(nA

)C

urr

en

t (m

A)

Voltage (V)

Cu

rre

nt

(mA

)

I’

IB

b

c

a

TiO2Ti

TiOxPt

Pt

-30

-25

-20

-15

-10

-5

0

x10-9

1.00.50.0-0.5-1.0

IIC

urr

en

t (n

A)

Cu

rre

nt

(mA

)

Voltage (V)

Cu

rre

nt

(uA

)

II’

IIB

TiOxTi

TiO2Pt

Pt

e

f

d

TiOx

Pt

TiO2

Pt

TiO2

Pt

TiOx

Pt

7 n

m7

nm

5 n

m

12

Schottky barrier switching via oxygen vacancy drift

TiOx

Pt

TiO2

Pt

7 n

m7

nm

TiO

2P

t

w

Φb

TiO

2P

t

w

Φb

TiO

X

-20

-10

0

10

x10

-3

2.01.00.0-1.0

Cu

rre

nt

(mA

)

II’

-20

-10

0

10

x10

-3

2.01.00.0-1.0

Cu

rre

nt

(mA

)

II’

page 13

Pt PtTiO2 TiO2-x

3 nm

2 n

m

O vacancy drift model for TiOx switch

Pt PtTiO2 TiO2-x

oxidizedreduced

As fabricated, the oxide has a highly resistive TiO2 region and a conductive TiO2-x region that is highly doped with O vacancies, which are positively charged.

When a positive bias voltage is applied to electrode 2, the positively charged O vacancies drift to the left, which narrows the tunneling gap.

3 – Theory of vacancy drift fits experiment

page 14

O vacancy drift model for TiOx switch

page 15

O vacancy drift model for TiOx switch

L

undoped

wV

doped

A

-4

-2

0

2

4

Curre

nt (m

A)

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5Voltage (V)

-1

0

1

volta

ge

1.61.20.80.40.0 x101

1.0

0.5

0.0

w/L

1.61.20.80.40.0time (×10

3)

-1.0

-0.5

0.0

0.5

1.0

curre

nt

-1.0 -0.5 0.0 0.5 1.0voltage

ROFF/RON = 50v0 = 4 V

-4

-2

0

2

4

Curre

nt (m

A)

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5Voltage (V)

123

45

6

7

8

9

10

17

PtTiPt

PtTiPt

Expt Expt

16

1. Nano-device switching is due to TiOx

2. TiOx switching is controlled by oxygen vacancy distribution- TiOx is a semiconductor doped by oxygen vacancies- charged oxygen vacancies drift under high field- deliberate placement of oxygen vacancies can engineer the switching-> electroforming is a critical device step

3. Dynamic theory of oxygen vacancy drift fits experiment- oxygen vacancy distribution controls electron conductivity- vacancy drift modulates junction conductance- fundamental memristor theory matches experiment-> detailed dynamics are highly nonlinear

4. New nano-circuits enabled by these nano-switches- NVRAM- latch circuits- adaptive signal conditioning

Metal/TiOx/Metal Device Physics

17

3D - No Transistors

• In ultra-dense nanoelectronic memory arrays, instead of the transistor “T.” a two terminal non-linear diode-like element may be used with a resistive memory element. Such structure is represented as 1D1R technology.

18

Where Silicon can’t go

•3D•Nonvolatile

19

Vision for Future Hybrid Chip:Vision for Future Hybrid Chip:CMOS/NanoElectronicsCMOS/NanoElectronics

Si CMOS

Multi-layers

Atomic SwitchCrossbar