nanoscale silicon based nonvolatile memory...2003/10/14 · of technology drain source gate sonos...

Chungwoo Kim, [email protected]

N anoscale N anoscale Silicon B asedSilicon B ased N onvolatile M em ory N onvolatile M em ory

C.W. Kim, KOREA-US Nano Forum, Oct. 14, 2003 ADVANCED INSTITUTEOF TECHNOLOGY

AcknowledgementsAcknowledgements

Seoul Nantional University (SNU)

Prof. Park, Byung-GooK

Korea Institute for Advanced Study

(KIAS)

Prof. Kim, Dae Mann

Kwangju Institute of Science andTechnology (KJIST)

Prof. Hwang, Hyun sang

Sungkyunkwan University

Prof. Chung Ilsub

Cornell University, USAProf. Sandip Tiwari

Institute of Semiconductor Physics,RussiaProf. Vlradmir Gritsenko

Collaboration

Funding

Tera-level Nanodevices21st Century Frontier R&D Program,Ministry of Science and Technology

SEC and SAIT


Introduction

Current research status– Nano fabrication Process

• Nanoscale patterning• SiN thin film• Si Nanoparticle

– Nano devices• Nanoscale SONOS memory• Vertical channel memory

Future Work

OutlineOutline


New application, unification – Diversfied from PC into digital application – Increasing capacity of voice, motion picture information ➙ Need higher density of memory – Increasing demand for unified memory

Uncertainty of DRAM & Flash Memory scalability

Memory Market: $35 billion (2001), $72 billion (2010), 8.3% increase/year

Environment of MemoryEnvironment of Memory

Settopbox

PDAHHP Internet

PC

DigitalTV

GamePlayer


Flash Memory RoadmapFlash Memory Roadmap(Source: ITRS 2001)

nm

1995 2000 2005 2010 2015

100

30

Feat

ure

Siz

e

Year

Unit CellProduction

Uncertain Stage

Research Stage

64-512MDevelop. Stage

130

180

70

50

150

10

128-512M

128M-1G256M-1G

256M-2G512M-4G

512M-4G

2G-16G

4G-64G

Scale limit ?


참고자료 : ITRS 2001

Year of Production

Flash tech. Node, F[nm]

NAND highest W/E Voltage[V]

NOR highest W/E Voltage[V]

NOR tunnel dielectric thickness[nm]

NAND tunnel dielectric thickness[nm]

NOR interpoly dielectric thickness[nm]

NAND interpoly dielectric thickness[nm]

2001 2002 2003 2004 2005 2006 2007

150 130 115 100 90 80 70

8-10 8-10 7-9 7-9 7-9

19-21 18-20 17-1918-20 18-20 18-20 17-19

8-10 8-10

9.5-10.5 9.5-10 9-10 9-10 8.5-9.5 8.5-9.5 8.5-9.5

8.5-9.5 8.5-9 8-9 8-9 8-9 7.5-8 7.5-8

13-15 12-14 11-13 11-13 10-12 9-11 9-11

14-16 13-15 12-14 12-14 12-14 11-13 10-12

Solutions ExistSolutions are Known

Solutions are NOT Known

Flash Technology RequirementsFlash Technology Requirements

(Source: ITRS 2001)


What’s the limits of flash scaling ?

Floating poly Stack

Active (STI)

Problems of conventional technologies


OvercomeOvercomeControl GateBlocking oxide

eTunnel Oxide

eeee

Discrete traps

n+ n+

p-well

SONOS Memory

Control GateBlocking oxide

n+ n+

p-well

Tunnel Oxide

Floating gate

ee e

기존 Flash memory

e ee ee e

☞ Discrete traps (SiN traps or Nanocrystal)

Discrete trapsDiscrete traps

* SONOS (Silicon-Oxide-Nitride-Oxide-Silicon)


< Advantages >• Compatibility of SONOS with CMOS with the use of thin nitride

• Lower programming voltage

• Smaller dimension capability than FG EEPROM

• Longer retention & low defect induced tunneling leakage

(Nitride instead of poly Si )

• Higher programming speed (depends on ONO thickness)

Trap sites

p-Si

Gate

30nm

S D

30 nm

US Patent # 6313503 (2001.11.6)

Motivation for SONOSMotivation for SONOS


4~10 F2

20~120 ns

1 µs ~ 1 ms

>10년

> 1E5

6 F2

10~100 ns

10~100 ns

> 10년

> 10E13

8~9 F2

10~100 ns

10~15 ns

> 10년

> 1E13

FRAM

8~25 F2

30~200 ns

30 ns

> 10년

> 10E12

Cell size

Read time

Write time

Retention

Endurance

Thin Oxide filmFaster P/E time

Power consumption

Etching processUniform thin filmsCost

Issues

MRAM PRAM SONOS

LowHighHighLowCurrent/Power

LowLowHighHighCost

CMOSSpecialSpecialSpecialProcess

Etching processCostRetention, Fatigue

Comparison of Memory TechnologiesComparison of Memory Technologies


2001

ChannelLength

130 nm130 nm

70 nm70 nm

30 nm30 nm

2002 2003

Source

DrainGate

70nm

SONOS Memory DevelopmentSONOS Memory Development


Nano Nano LithographyLithography

20nm 60nm

21 nm

32 nm

Sidewall Patterning

Positive Resist : PMMA

Negative Resist : Calixarene


Si Nanoparticle Si Nanoparticle Fabrication by Aerosol Laser AblationFabrication by Aerosol Laser Ablation

0 10 20 30 40 50 60 70 800

1x104

2x104

3x104

4x104

5x104

6x104

C

once

ntra

tion

(/cm

3 )

Nanoparticle Size (nm)

• D <10nm

• ρ ~ 1×1011 /cm2

5nm 5nm


3030nm SONOS Memory by SWPnm SONOS Memory by SWP

10-7 10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 103-2.0-1.5-1.0-0.50.00.51.01.52.02.53.0

Vg=10

Vg=-10/Vd=4Vg=-10/Vd=3Vg=-10/Vd=2Vg=-10/Vd=1

ONO=23/120/45 Å

Vg=-10

Thr

esho

ld V

olta

ge [V

]

Write/Erase Time [Sec]

Key Features of SONOS CellMemory Node Size: 30 x 30 nm2

Write/ Erase Voltage: <10V

Write/Erase Time: 1 msec

Endurance: >106 cycles

Retention = 1year @T=85℃


Key Characteristics of SONOS MemoryKey Characteristics of SONOS Memory

-1.0 -0.5 0.0 0.5 1.01E-14

1E-13

1E-12

1E-11

1E-10

1E-9

1E-8

1E-7

1E-6

Vth=-0.05V

W/L=30nm/30nmONO=23/120/45 A

VDS=1V

VDS=0.1V

S.S = 89mV/decDIBL = 105mV

Drai

n Cu

rren

t [A]

Vgs [V]

0.0 0.2 0.4 0.6 0.8 1.00.00E+000

4.00E-008

8.00E-008

1.20E-007

1.60E-007

2.00E-007

2.40E-007

2.80E-007

3.20E-007

3.60E-007

ONO=23/120/45 Å 1.0V0.8V

0.6V

0.4V

0.2V

VGS=0V

Drai

n Cu

rren

t [A]

Vds [V]

10-2 10-1 100 101 102 103 104 105 106 107 108-2

-1

0

1

2

3

1.4 [V]

Time [sec]

Vth

[V] At 85C

@ Program state @ Erase state

100 101 102 103 104 105 106

-1.0

-0.5

0.0

0.5

1.0

1.5

Programmed @10V/1ms Erased @-10V/10ms

Vth

(V)

Cycles (number)


Drain

Source

Gate

SONOS Memory by E-beam LithographySONOS Memory by E-beam Lithography

SONOS Cell by E-beam Lithography

W/L : 33nm / 46nm


20Å / 70Å / 90Å

SiO2= 20ÅSi3N4= 70Å

SiO2=90Å

• TEM of the ONO (2 nm/7 nm/9 nm) stack• Auger profile showing the stoichiometric of ONO layer.

ONO layer TEM & AES AnalysisONO layer TEM & AES Analysis

0 3000 6000 9000 12000 15000 18000

0

20

40

60

80

100

Rel

ativ

e AC

P(%

)

Si N O

Sputter Time [sec.]


1E-7 1E-6 1E-5 1E-4 1E-3 0.01 0.1 1-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

Th

resh

old

Vo

ltag

e[V

]

Write Time[sec]

|9V| |10V| |11V| |12V| |13V|

1E-7 1E-6 1E-5 1E-4 1E-3 0.01 0.1 1

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

Th

resh

old

Vo

ltage

[V]

Erase Time[sec]

|9V| |10V| |11V| |12V| |13V|

∆Vth ~ 2.4V

Trapped Charge density = 4.1 ~ 5.9 x 1012 cm –2

No. of e- = 61 ~ 88 for 33nm x 46nm node size

∆Vth ~ 2.4V

Trapped Charge density = 4.1 ~ 5.9 x 1012 cm –2

No. of e- = 61 ~ 88 for 33nm x 46nm node size

Program & Erase Program & Erase CharacterisicsCharacterisics


• Memory window is nearly similar for SONOS devices with different memory node areas

Memory Window ComparisonMemory Window Comparison

-2 -1 0 1 2 3 4 5 6 7 8 9 1010-15

1x10-14

1x10-13

1x10-12

1x10-11

1x10-10

1x10-9

1x10-8

1x10-7

1x10-6

1x10-5

Wg/L

g=90nm / 100nm

Id

[A]

Vg [V]

Wg/Lg=90nm/100nm

-2 -1 0 1 2 3 4 5 6 7 8 9 1010-15

1x10-14

1x10-13

1x10-12

1x10-11

1x10-10

1x10-9

1x10-8

1x10-7

1x10-6

1x10-5

Wg/L

g=75nm / 100nm

Id [A

]

Vg [V]

Wg/Lg=75nm/100nm

-2 -1 0 1 2 3 4 5 6 7 8 9 1010-15

1x10-14

1x10-13

1x10-12

1x10-11

1x10-10

1x10-9

1x10-8

1x10-7

1x10-6

1x10-5

Wg/L

g=62nm / 60nm

Id [A

]

Vg [V]

Wg/Lg=62nm/60nm

-2 -1 0 1 2 3 4 5 6 7 8 9 1010-15

1x10-14

1x10-13

1x10-12

1x10-11

1x10-10

1x10-9

1x10-8

1x10-7

1x10-6

1x10-5

Wg/L

g=33nm / 46nm

Id [A

]

Vg [V]

Wg/Lg=33nm/46nm


• Retention time is good with 75nm width and 100 nm length at 85℃.

Retention TimeRetention Time EnduranceEndurance

10-1 100 101 102 103 104 105 106 107 108 1090.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Wg/Lg=75nm / 100nm

Temp=85C

Thre

shol

d Vo

ltage

[V]

Retention Time[sec]

Write 10V, 10msec Erase -10V, 1msec

101 102 103 104 105 1060.6

0.8

1.0

1.2

1.4

1.6

1.8

Temp=85C

Wg/L

g=33nm / 46nm

Thre

shol

d Vo

ltage

[V]

Write/Erase Cycle

Write 12V/10msec Erase -10V/1msec

• It remains unchanged up to 105

cycles, indicating superior endurance characteristics at 85℃.


• Single electron charging effect at 30 nm dimensions.

Memory Effect at 30 nm dimensionsMemory Effect at 30 nm dimensions

Wg = 35.4 nm Lg = 39 nm-1 0 1 2 3 40.0

2.0x10-10

4.0x10-10

6.0x10-10

8.0x10-10

1.0x10-9

1.2x10-9

1.4x10-9

Wg/Lg=35nm / 39nm

Before write After write(10ms,|10V|)

ID [A

]

VG [V]


Vertical Channel SONOS

N+ N+

Poly Silcon

BOX

Schematic of VC SONOS

1E-41E-3 0.01 0.1-0.8

-0.4

0.0

0.4

0.8

1.2

1.6

2.0

0.001

Vg 6/7/8V

Erased Cell

Programmed Cell

Vg -6/-7/-8V

V th (V

)Write/Erase Time(sec)

Id=1nA, Vd=0.5V

• ∆Vth=1.6V @ 8/-8V &10ms


TEM images

Gate

CVD oxide

Verticalchannel

O/N/O

ContactVertical channel

bulk

Drain

Source

Gate

source draingate


Nano fabrication process for Integration

Improvement of SONOS memory characteristics

– High-k materials

– New memory cell structure

– Optimal bias conditions

Device physics– Single electron effect

– Reliability failure mechanism

– Memory cell Modeling/Simulation

Future WorkFuture Work

nanoscale silicon based nonvolatile memory...2003/10/14 · of technology drain source gate sonos...

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