engineering of oxide-based materials

8/11/2019 Engineering of Oxide-based Materials

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Copyright 2010 Hewlett-Packard Development Company, L.P. Based on PowerPoint Template version1.0

1

ENGINEERING OF OXIDE-

BASED RESISTIVE SWITCHI

NG

MATERIALS

Byung Joon Choi

Dept. Mater. Sci. Eng.

Seoul National University of Science and Technology

bjchoi@seoultech ac kr

Workshop on

Oxide Heterostructures 2014


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2

Outline

1. Introduction: new electronic RRAM

2. Electrical performance and scaling

3. Mechanism

4. Summary future work


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Surging needs for high density memory

Compute-centric Data-centric

Devices 5.6M disk 21M disk

Space 26,292 ft2 98,568 ft2

Power 25 MW 93 MW

Storage system 2020 for server computer

R. F. Freitas and W. W. Wilcke, IBM J. Res. Dev. 52, 439 (2008)

Paradigm shift: compute-centric

data-centric era

Ever increasing demand for high density memory!


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Next Generation Memory

Figure from IBM Research at Almaden

110

102

103

10

4

105

106

107

108

109

1010

SRAM

DRAM

Flash(SSD)

HDD

Tape

Memory type

DRAM

Next

Gen.

Memory


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PCRAM & RRAM

J. J. Yang et al. Nature Nanotechnol.8, 13 (2013)G. W. Burr et al. JVST B28, 223 (2010)

Next generation memory? 3-D crossbar memory!

Multiple

stacking(x N)

Phase Change RAM

Resistive RAM

and/or


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R. Waser et al.Adv. Mater.21, 2632 (2009)

K. M. Kim et al. Nanotechnology22, 254002 (2011)

Materials: Metal oxides,

Chalcogenides

Switching:

Low R High R

Emerging technology

High potential, but unclear

Resistive Random Access Memory (RRAM)

Connect

(Low R)1

Disconnect

(High R)0

Strong Candidate: RRAM


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O2-

O2-

O2- O2- O2-

-V

G

ee

-V

G

Electronic RRAMMore reliable and faster!


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Concept: Nanometallicity

Random system : aperiodic

Andersons : Electron diffusion distance

Metal:

Insulator: <

Metallic if d< Insulating if d>

d : sample size

P.W. Anderson, Phys. Rev. 109, 1492 (1958)A. Chen et al.Nature Nanotech.6, 237 (2011)

Philip W. Anderson

Nobel Prize in Physics (1977)


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0.00 0.25 0.500

25

50

f

(nm)

Conducting

Insulating

Percolation Threshold

Materials design: Pt-dispersed SiO2

SiO2:PtPt

Mo

Nanometallicity

-6 -3 0 3 6-20

-10

0

10

20

100

1k

10k

100k

1M

I(mA

)

V(V)

R

(

)

I-VR-V

V-triggered MIT

A. Chen et al. Nature Nanotech.6, 237 (2011)

MIT controlled by thickness (d) and concentration (f)

Purely electronic switching proposed

PtSiO2


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Device performance: Reliable

B. J. Choi et al.Ad v. Mater.23, 3847 (2011)

B. J. Choi et al.Nano Lett. 13, 3213 (2013)

10

-4

10-3

10-2

Current(A)

2.01.00.0-1.0

Voltage (V)

Excellent uniformity and high durability

Much more reliable than any other ionic RRAMs

0.01 0.1 10.1

1

10

100

k

/

(1)

(2)

(3)

(4)

(1) R HRS(DC)

(2) R HRS(AC)(3) V off(4) -V on

More uniformSiO2:Pt

1000 DC cycles

Pt

SiO2

SiO2: PtTa


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100psswitching speedFaster than ionic RRAM

Highly reliable fast switching

Device performance: Fast

BETE

Transmission line

Transmission line

Device

ON switching

(same w/ OFF)Memory



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Device performance: Scalable

100nm

10-9

10-8

10-7

10-6

10-5

10-4

Current(A)

-4 -2 0 2

Voltage (V)

1stON

Semi-

log scale

OFF

Scalability proved down to (100nm)2

Uniform, high ON/OFF ratio

No change up to 6 months10

010

210

410

610

8103

104

105

106

107

108

Resistan

[email protected]

V()

time (s)

6 months



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Resistance and switching voltage with scaling?

Switching mechanisms? (purely electronic?)

Can replace Pt?

How reliable?

How fast?

How scaled?

Mechanism?Other materials?

SiO2:PtTE

BE

Key questions


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0 5 10 15 20 25 30 3510

-1

101

103

105

107

109

f= 0.33

f= 0.27

f= 0.20

RHRS

()

d(nm)

RHRS exp(d

/HRS)

*B. I. Shklovskii, A. L. Efros, Springer, Heidelberg (1984)

B. J. Choiet al.Adv. Mater.23, 3847 (2011)

Scaling theory in random materials*exponential dependence on d

Localization length, HRS, can be tuned by Pt concentration, f

Device resistance: f, d,A

10-6

10-5

10-4

102

104

106

108

1010

27nm

20nm

17nm

Resistance()

Area (cm2)

Rl ine(> LRS)

HRS

RHRS 1/A


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10-11 10-9 10-7 10-510

1

103

10

5

107

109

Resista

nce()

Area (cm2)

f= 37.5%

f= 45%

Scaling projection

RHRSinversely

proportional to the device

area

Uniform electric

conduction under RHRSNon-uniform conductionunder RLRS

(7nm)



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Voltage induced switching (trapping/de-trapping)f (V)(fraction of HR element): state variable

n(total number of R element): determined by device area, concentration,

and thickness of film

LH

electrodeRnfRnf

RR/)1(/

1

B. J. Choi, A. Chen, X. Yang, I-W. Chen, unpublishedA. Chen, B. J. Choi, X. Yang, I-W. Chen,Adv. Funct. Mater.22, 546 (2012)

Parallel circuit model


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19

Outline

1. Introduction: new electronic RRAM

2. Electrical performance and scaling

3. Mechanism

4. Summary future work


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: Free electron path

: Isolated trap sites Trap filled

decreases

T3

T2

T1

electron flow

TE

BE

LRS

T2

T1

T3

electron flow

TE

BE

HRS

Mechanism: Trapping-mediated localization


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-6 -3 0 3 6

100

10k

1M

100M

R(

)

V(V)

21 nm

12 nm9 nm

7 nm5.5 nm

-6 -3 0 3 6

10k

1M

100M

20%

25%

32%36%

R

()

V(V)

42%

Nanoscale MIT

d-triggered (SiO2:20%Pt)

f-triggered (d~20 nm)

Sameswitching voltage always!


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10 20 30 4010

1k

100k

10M

LR

R

(

)

(nm)

HR

CS

I

Electronic MIT: f--Tindependent

-4 -2 0 2 4-2

-1

0

1

2

293K

I(mA)

V(V)

10K

6 8 10 12 14 16

4

5

5000 10000 15000 20000

4

5

15 20 25 30 35

4

Voff

(V)

f, d, cell size

(%)

(nm)

(m2)

f

d

cell size

Switching voltage : temperature

independent

HR temperature dependence :

insulating


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UV-irradiation resets memory: Electronic

UV light

Pt

SrRuO3or Mo

Fused SiO2Alloy Film

0 50 100100

1k

10k

100k

R

(

)

Time (sec.)

UV on

0 20 40 60

1k

10k

100k

R(

)

Time (sec.)

UV on

UV source : 300~420 nm (4.2-3.0 eV)

HRS switches to LRS

LRS unchanged

Electronic switching confirmed

Notan ionic effect


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Pressure resets memory: electron-phonon

X. Yang, I. Tudosa, B. J. Choi, A. Chen, I.-W. Chen,Nano Lett. In press

Mechanically induced MIT

also one-way transition: HRSLRS, LRS unchanged

Electron-phonon interaction confirmed

P= 300 Mpa(Isostatic )


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Pressure resets memory: electron-phonon

X. Yang, I. Tudosa, B. J. Choi, A. Chen, I.-W. Chen,Nano Lett. In press

Source:20GeV

Electron bunch

(duration time

~ 0.24ps)

Electron bunch

Circulating I

Lorentz force

Tensile stress


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-4 -3 -2 -1 0

103

104

105

106

50ns

100ns

500ns

1s

100s

10ms

Resistance()

Voltage (V)

Overcoming Voltage-time dilemma

Voltage-time dilemma: fast programmable or long retaining, but not

both in electronic memory

No degradation of switching by using shorter pulse widths

On-switching (-)

0 1 2 3 4 5

103

104

105

106

Voltage (V)

twrite

:

100ns

1s

10s

100s

1ms

Off-switching (+)

B. J. Choi, A. Chen, X. Yang, I-W. Chen,Adv. Mater.23, 3847 (2011)


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Variability II: from switching device to device

Origin:

Different switching channels indifferent devices.

Solution:

Plant similar seeds (nanoclusters)

of switching channels in different

devices

facilitate similar switching

channels formed in every device.

Engineered Switching Materials


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Summary

A. Chen et al. Nature Nanotech.6, 237 (2011)

B. J. Choi, A. Chen et al.Adv. Mater.23, 3847 (2011)

A. Chen, B. J. Choi, et al.Adv. Funct. Mater.22, 546 (2012)

1. A new electronic switching in SiO2:Pt

B. J. Choiet al. Nano Lett. 13, 3213 (2013)

B. J. Choi, I-W. Chen,Appl. Phys. A(2013)

X. Yang, B. J. Choiet al.ACS Nano7, 2302 (2013)

X. Yang, A. Chen, B. J. Choi, I-W. Chen,Appl. Phys. Lett. 102,

043502 (2013)

X. Yang, I. Tudosa, B. J. Choi, A. Chen, I.-W. Chen,Nano Lett. In

press

2. Performance and mechanism investigated

10-9

10-8

10-7

10-6

10-5

10-4

Current(A)

-4 -2 0 2

Voltage (V)

0.01 0.1 10.1

1

10

100

k

/

uniform

SiO2:Pt


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Future work

Smaller is better!

What? Different conducting and insulating materials

How? Processing (ALD, implantation, annealing, etc.)

Why?Physics and thermodynamics

A source :

B source :

A source feeding Purge

Purge B source feeding

Materials & Processing


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Acknowledgements

Prof. Cheol Seong Hwang (SNU)

Prof. I-Wei Chen (UPENN)

Dr. Jianhua Joshua Yang (HP)

Dr. Richard Stanley Williams (HP)Many colleagues

engineering of oxide-based materials

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