A Study on Formation of High Resistivity Phases of …...Resistivity [mW・cm] C54:13~20, C49:80~100...

1

A Study on Formation of High Resistivity Phases of Nickel Silicide at Small Area and its

Solution for Scaled CMOS Devices

Doctor Thesis

Ryuji Tomita

Supervisor : Prof. Iwai

2

Outline

Back ground

Purpose of this work

Configuration of this thesis

Chapter 3~6

Conclusion

3

MOS Scaling and SALICIDE

Si Substrate

Well

STI

Si Substrate

Well

STI

Scaling :k (

4

Titanium SALICIDE

Ti

Si

a-TiSix

Si

C49-TiSi2 80-100 mW cm

C54-TiSi2 13-20 mW cm

Si Si

>700℃ 500 – 600℃

400 -

500℃

*J.A. Kittl , W.T. Shiau, Q.Z. Hong, D. Miles

Microelectronic Engineering 50 (2000) 87–101

Limitation of TiSi2 as scaling

1. Difficulty in transforming C49 to C54 TiSi2. 2. Low thermal stability as thinning.

3. Si is dominant diffusion specie.

The first SALICIDE material used in fabrication.

5

Cobalt SALICIDE

Limitation of CoSi2 as scaling

1. Large Si consumption. 2. Rough interface by nucleation control.

3. High formation temperature of CoSi2.

4. Si is dominant diffusion specie in CoSi.

Co

Si

Co2Si 110 mW cm

Si

CoSi 147 mW cm

CoSi2 15-20 mW cm

Si

Si

700℃ 375℃ 350℃

*H. Iwai, T. Ohguro, and S.-i. Ohmi, NiSi salicide technology for

scaled CMOS, Microelectronic Engineering 60, 157 (2002).

Cobalt SALICIDE has better scalability than Titanium SALICIDE.

6

Nickel SALICIDE: Superiority

Ni

Si

Ni2Si 110 mW cm

Si

NISi 147 mW cm

NiSi2 15-20 mW cm

Si

Si

700 -

800℃ 300

-400℃ 250

-300℃

Superiority of Nickel SALICIDE

1. low Si consumption

2. low formation temperature

3. Ni diffusion kinetics

TiSi2 CoSi2 NiSi

Resistivity [mW・cm] C54:13~20, C49:80~100 14~20 10.5~18

Formation Temperature 600~700℃ 600~700℃ 300~400℃

Dominant moving species Si Co(Si) Ni

Si consumption ratio 2.27 3.64 1.83 *参考 Silicide Technology for Integrated Circuits L.J. Chen

7

Nickel SALICIDE: Issues for practical use Critical Issues of Nickel SALICIDE

1. Controlling phase formation

2. Controlling and limiting diffusion of Ni in Si

3. Poor thermal stability of NiSi

4. Oxidation of NiSi

5. Reducing the specific contact resistivity

Phase Resistivity

(mW・cm)

Ni 7-10

Ni3Si 80-90

Ni31Si12 90-150

Ni2Si 24-30

Ni3Si2 60-70

NiSi 10.5-18

NiSi2 34-50

Silicide Phase and Resistivity

*参考 Silicide Technology for Integrated Circuits, L.J. Chen

Series Resistance v.s. Gate Length

*J-G Yun et al. Japan Journal App. Phy.Vo43, pp.6998 2004

*M Tsuchiaki et. al.

Japan Journal App. Phy.

Vo44, pp.1673 2005

*S-D Kim et al. TED2002

8

Purpose of this work

Following issues of Nickel silicide

are investigated.

1. Phase control of nickel silicide at

small areas.

2. Thermal stability of NiSi.

3. Schottky barrier height lowering at

NiSi and silicon interface.

9

Configuration of this thesis

Chapter 1 Introduction

Chapter 4

Improvement on

Uniformity

of Sheet Resistance

Chapter 7 Summary and

Conclusions

Chapter 6

Schottky Barrier Height

between NiSi and Si

Interface

Chapter 5

Thermal Stability

of NiSi

Chapter 2 Fabrication and Characterization Method

Chapter 3

High Resistivity of

Nickel Silicide

at Small Area

Chapter 2 CMOS Silicide Process Flow

and Sheet Measurement Pattern

Sectional view of test structure Top View of test structure

L=0.5～100mm W=0.10 ～ 1.0mm

STI or Side Wall

silicide

V I

silicide

contact

Substrate or Poly-Si

STI or

Side

Wall

STI, Gate, Junction, Wet Clean

Ni/TiN sputter:Ni→TiN in-situ

1st Anneal:270℃ 150sec heating up by hot plate

Selective Wet Etch:SPM(H2SO4+H2O2)

2nd Anneal:395℃ 30sec hold

Contact, Cu Interconnects

11

Chapter 3 High Resistivity Phase of

Nickel Silicide at Small Area

Purpose of this chapter

Understanding the formation of high resistivity

phase of Nickel silicide at small area.

Identified nickel silicide phase

Compared to CoSi2

Reaction Mechanism and Thermodynamics of nucleation

12

Width dependence of Sheet Resistance

Sheet resistance increase in only narrow line.

n+ active area (L=100mm) p+ active area (L=100mm)

0

5

10

15

20

0.1 1 10

Sh

eet

Res

ista

nce

[ W

/sq

]

Width [ mm ]

Mid

Max

Min 0

5

10

15

20

0.1 1 10 S

hee

t R

esis

tan

ce [

W/s

q ]

Width [ mm ]

Mid

Max

Min

13

Sheet Resistance on n+ Active Areas

0 5 10 15 20 25 30 35.01

.1

1

5102030

50

70809095

99

99.9

99.99

L=0.5um

L=5.0um

L=10um

L=100um

Sheet Resistance[ohm/sq.]

Cu

mu

lati

ve p

rob

abil

ity

[%]

W=1.0mm

0 5 10 15 20 25 30 35.01

.1

1

5102030

50

70809095

99

99.9

99.99

L=0.5mm

L=5.0mm

L=10mm

L=100mm


Cu

mu

lati

ve p

rob

abil

ity

[%]

W=0.10mm

TEM

&NBD

(a)

(b) (a) L/W=0.5/0.10mm. 6.4W/sq.

(b) L/W=0.5/0.10mm. 19.5W/sq.

Si 200

Si 111

NiSi

102

NiSi

010

NiSi

112

(a) NBD

Thickness:21.8nm, Resistivity:14.0mm・cm


Ni3Si2

311

Ni3Si2

311

Ni3Si2

020

(b) NBD

*NBD: Nano Beam Diffraction *Ni3Si2: JCPDS 17-0881

High resistance sample has NiSi and Ni3Si2. Long line has NiSi only. No increase in resistance.

14

W=1.0mm

0 5 10 15 20 25 30 35.01

.1

1

5102030

50

70809095

99

99.9

99.99

L=0.5um

L=5.0um

L=10um

L=100um


Cum

ula

tive p

rob

abil

ity[%

]

W=0.10mm

0 5 10 15 20 25 30 35.01

.1

1

5102030

50

70809095

99

99.9

99.99

L=0.5mm

L=5.0mm

L=10mm

L=100mm


Cum

ula

tive p

rob

abil

ity[%

]

TEM

&NBD

(a)

(b) (a) L/W=0.5/0.10mm. 7.2W/sq.


(b) L/W=0.5/0.10mm. 27.0W/sq.

Thickness:19.4～59.9nm

NiSi

211

NiSi

102

NiSi

113

(a) NBD Si 200

Si 111

NiSi2

111

NiSi2

200

NiSi2

111

(b) NBD

Sheet Resistance on p+ Active Areas

High resistance sample has NiSi and NiSi2. Long line has NiSi only. No increase in resistance.

15

NiSi on poly also has degradation in uniformity.

⇒Not crystal states of Si but size of area is dominant.

Sheet Resistance on Poly-Si n+ poly (W=0.11mm) and

n+ active area (W=0.10mm)

p+ poly (W=0.11mm) and

p+ active area (W=0.10mm)

0 5 10 15 20 25 30 35.01

.1

1

5102030

50

70809095

99

99.9

99.99

Npoly 1.0mm

Npoly 10mm

Npoly 100mm

Ndiff 1.0mm

Ndiff 10mm

Ndiff 100mm


Cum

ula

tive

pro

bab

ilit

y[%

]

0 5 10 15 20 25 30 35.01

.1

1

5102030

50

70809095

99

99.9

99.99

Ppoly 1.0mm

Ppoly 10mm

Ppoly 100mm

Pdiff 1.0mm

Pdiff 10mm

Pdiff 100mm


Cum

ula

tive

pro

bab

ilit

y[%

]

16

Comparison to CoSi2

n+ active area (W=0.10mm) p+ active area (W=0.10mm)

CoSi2 has no degradation in uniformity.

⇒Complex phase diagram of Ni-Si system is main cause in the formation of high resistivity phase.

0 5 10 15 20 25 30 35.01

.1

1

5102030

50

70809095

99

99.9

99.99

L=0.5mm

L=5.0mm

L=10mm

L=100mm

Sheet Resistance [ W/sq ]

Cum

ula

tive

pro

bab

ilit

y[%

]

0 5 10 15 20 25 30 35.01

.1

1

5102030

50

70809095

99

99.9

99.99

L=0.5mm

L=5.0mm

L=10mm

L=100mm


Cum

ula

tive

pro

bab

ilit

y[%

]

Presumed Ni-Si Reaction Path on n+ Area

17

Step Chemical

equation

ΔH

(kJ/mol of

Ni atoms)

Total Volume

Change

[(post-pre)/pre]

Volume Change

of Silicide

[(post-pre)/pre]

Volume

Expansion

[(Silicide-Si)/Si]

1 2Ni+Si→Ni2Si -66 -23.3% - 0.0%→60.5%

2 3Ni2Si+Si→2Ni3Si2 -9 -1.3% +19% 60.5%→43.5%

3 Ni3Si2→Ni2Si+NiSi +2.7 -2.1% -2.1% 43.5%→40.5%

4 Ni2Si+Si→2NiSi -19 -7.5% +50% 60.5%→20.5%

Reaction Step Model

1. Formation of Ni2Si. Increasing

compressive stress.

2. Formation of Ni3Si2. Relaxing stress.

Reaction is noticeable at fine patterns.

3. ΔH is small. Nucleation reaction like.

4. Formation of NiSi.

• Step3 is limiting step. Ni3Si2 tends to remain. • 2 reaction paths complicate phase sequence.

1:Ni2Si→NiSi, 2:Ni2Si→Ni3Si2→NiSi.

*Rivero et. al. Appl. Phys. Lett. 87, 041904 (2005)

18

Effect of Compressive Stress on silicidation *C. Rivero et. al, App. Phy. Lett. (2005)

147Å

92Å

175Å

122Å

220Å

183Å

Ni2Si Ni3Si2 NiSi

Silicon

ΔH=

-26.0(KJ/mol)

ΔH=

-10.3(KJ/mol)

Silicide /

Consumed

Si

1.61

(=147/92)

1.44

(=175/122)

1.20

(=220/183)

Large impurities; As, P, and Silicide stress.

⇒Compressive stress retards the reaction. *L.W. Cheng et al. / Materials Science and Engineering A 409 (2005) 217–222

⇒Difficulty in transition from Ni3Si2 to NiSi.

Presumed Ni-Si Reaction Path on p+ Area

19

Step Chemical

equation

ΔH

(kJ/mol of

Ni atoms)

Total Volume

Change

[(post-pre)/pre]

Volume Change

of Silicide

[(post-pre)/pre]

Volume

Expansion

[(Silicide-Si)/Si]

1 Ni+2Si→NiSi2 -87 -22.5% - 0.0%→-1.4%

2 3Ni+NiSi2→2Ni2Si -10.5 -11.1% +62.8% -1.4%→60.5%

3 NiSi2+Ni2Si→3NiSi -12 +1.0% +1.0% 19.3%→20.5%

4 NiSi2→NiSi+Si +2 -11.8% -38.9% -1.4%→20.5%

Reaction Step Model

1. Formation of NiSi2. Small stress. Thickness of

NiSi2 depends on implanted dose spices and

amounts. 2. Unreacted Ni and NiSi2 form Ni2Si. Large

stress is formed.

3. NiSi2 and Ni2Si form NiSi.

4. Without Ni, NiSi2 hardly transforms to NiSi.

Large amount B makes thicker NiSi2 layer. Thicker

NiSi2 tends to remain because of lack of Ni. *T. Isshiki et. Al. RTP 2006 14th IEEE International Conf. on RTP

20

Effect of Tensile Stress on silicidation

Implanted Boron and STI makes tensile stress.

⇒Tensile stress promotes the reaction. *L.W. Cheng et al. / Materials Science and Engineering A 409 (2005) 217–222

⇒NiSi2 is formed in early stage of silicidation.

Interfacial Energy increase by implanted B (?)

*W. J. Chen and L. J. Chen, J. App. Phys. (1991)

Si Substrate

Well

-Si-B-Si-B-Si STI

Small atom, B and STI

makes tensile stress.

21

Thermodynamics of Nucleation

Fre

e E

ne

rgy C

han

ge

Surface Energy S1+S2

Volume

Energy DG* t

DG*

t tco=

(S1+S2) / DG

(a) The free energy of a nucleus

as a function of its radius

Surface Energy

S1+S2+SB

tc1= (S1+S2+SB) / DG

(b) The free energy of a nucleus

When uniform planer film

Boundary surface increases free energy change

→ nucleation reaction is promoted at small areas.

*S1:Surface Energy

S2:Interface Energy

SB:Interface Energy of boundary

*F.M. d’Heurele J. Mater. Res. 3(1), 1988, pp.167-195

Fre

e-E

nerg

y C

hange [

DG

]

r

Surface

bsr2

Volume

aDGr3

r*

DG*

r

S2

SB

S1

t

22

Comparison between TiSi2 and NiSi cases

Ni2Si Ni3Si2

Reaction C49-TiSi2→C54TiSi2 Ni2Si→Ni3Si2→NiSi

Figure

Reaction

Mechanism

TiSi→C49-TiSi2→C54TiSi2 Sequential reaction.

1. Ni2Si→NiSi

2. Ni2Si→Ni3Si2→NiSi

2paths to form NiSi.

Volume Change

by reaction

-2%

C49-TiSi2→C54TiSi2

+50%

Ni2Si→Ni3Si2→NiSi

Effect of Scaling on

Phase Transition

Transition from C49 to C54-

TiSi2 is difficult for decreasing

nucleation sites.

Ni2Si→Ni3Si2 reaction is

promoted at small area for

stress reduction.

*T. Isshiki et. Al. RTP 2006 14th

IEEE International Conf. on RTP

*J. A. Kittl et. Al. Microelectronics Eng.

Vol.50. pp.87-101(2000)

Formation of NiSi is much complex than TiSi2 case in terms of stress formation and reaction mechanism.

23

Conclusions of Chapter 3 Firstly, formation of Ni3Si2 on small n

+ or NiSi2 on small p

+ active and poly-Si areas is confirmed.

The formation of high resistivity phases at small areas is characteristic features of nickel silicide which has complex phase diagram and reaction mechanism.

Tensile or compressive stress affects the formation of NiSi2 and Ni3Si2 respectively.

24

Chapter 4 Improvement on

Uniformity of Sheet Resistance


Modify silicidation conditions in order to

improve the uniformity of sheet resistance

at small area.

25

Effect of First Anneal

0 5 10 15 20 25 30 35.01

.1

1

5102030

50

70809095

99

99.9

99.99

270oC

280oC

290oC

320oC

350oC


Cum

ula

tive p

rob

abil

ity[%

]

n+ active area W/L=0.10/0.5mm

0 5 10 15 20 25 30 35.01

.1

1

5102030

50

70809095

99

99.9

99.99

270oC

280oC

290oC

320oC

350oC


Cum

ula

tive p

rob

abil

ity[%

]

p+ active area W/L=0.10/0.5mm

Only p+ active area is improved.

*Process condition 2nd Anneal 395oC

26

200

200

111

111 111

111

NiSi2 1 304

304

600

304

600

304

NiSi 2

Si 220

Si 220 Si 220

Si 220

Si 4 204

212 412

412

212

204

NiSi 3

1 2

4

3 L/W=0.5/0.10mm. 11.7W/sq at 575℃

Effect of second anneal on n+ active area

0 5 10 15 20 25 30 35.01

.1

1

5102030

50

70809095

99

99.9

99.99

395oC

500oC

550oC

575oC


Cu

mu

lati

ve p

rob

abil

ity

[%]

N+diff. W/L=0.10/0.5mm

TEM

&NBD

Not Ni3Si2 but NiSi2 is formed.

*Process condition 1st Anneal 270oC

27

NiSi2

220

220

220

220

020

200 020

200

1

220

220

220

220

020

200 020

200

NiSi2 2

Si 220

Si 220 Si 220

Si 220

Si 4 NiSi2

220

220

220

020

200 020

200

220

3

Effect of second anneal on p+ active area

0 5 10 15 20 25 30 35.01

.1

1

5102030

50

70809095

99

99.9

99.99

395oC

500oC

550oC

575oC


Cu

mu

lati

ve p

rob

abil

ity

[%]

P+diff. W/L=0.10/0.5mm

TEM

&NBD

1 2

4

3

L/W=0.5/0.10mm. 14.8W/sq. at 575℃

Epi-NiSi2 is formed.


28

Effect of Nickel Thickness n+ active area W/L=0.10/0.5mm p+ active area W/L=0.10/0.5mm

thicker Ni increases volume energy.

*Process condition 1st Anneal 270oC /2nd Anneal 395oC

0 5 10 15 20 25 30 35.01

.1

1

5102030

50

70809095

99

99.9

99.99

80A60A100A


Cu

mu

lati

ve

pro

bab

ilit

y [

%]

0 5 10 15 20 25 30 35.01

.1

1

5102030

50

70809095

99

99.9

99.99

80A60A100A


Cu

mu

lati

ve

pro

bab

ilit

y [

%]

29

n+ Active Area after 1st Anneal Sample1 L/W=0.5/0.10mm

002

320

322

Ni2Si

301 320

021

Ni2Si

242 551

313

Ni3Si2

Both Ni3Si2 and Ni2Si are identified.

⇒Process before 1st Anneal should be improved.


30

High Temp. Ni PVD on n+ active area N+diff. W/L=0.10/0.5mm

0 5 10 15 20 25 30 35.01

.1

1

5102030

50

70809095

99

99.9

99.99

200oC SPT

300oC SPT

RT SPT


Cu

mu

lati

ve

pro

bab

ilit

y[%

]

TEM

&NBD

414 123

511

NiSi2

111

113 224

NiSi2

422

531 113

NiSi2

220 400

Si

High resistance sample, 18.2W/sq. of Ni PVD at 200℃

Not Ni3Si2 but NiSi2 is formed.

A B C

D

A B

D C


31

High Temp. Ni PVD on p+ active area P+diff. W/L=0.10/0.5mm

0 5 10 15 20 25 30 35.01

.1

1

5102030

50

70809095

99

99.9

99.99

200oC SPT

300oC SPTRT SPT


Cu

mu

lati

ve

pro

bab

ilit

y[%

]

TEM

&NBD

High resistance sample, 22.6W/sq. of Ni PVD at 200℃

200

020 200

020

NiSi2

200

020 200

020

NiSi2

200

020 200

020

NiSi2 220 400 Si

Epi-NiSi2 is formed.

A B C

D

A B

D C


32

Effects of Anneal Time

0 5 10 15 20 25 30 35.01

.1

1

5102030

50

70809095

99

99.9

99.99

270C REF.270C 2 times long


Cu

mula

tiv

e p

rob

abil

ity

[%

]

N+ Active Area

L/W=0.5/0.10mm

P+ Active Area

L/W=0.5/0.10mm

0 5 10 15 20 25 30 35.01

.1

1

5102030

50

70809095

99

99.9

99.99

270C REF

270C 2 times long


Cum

ula

tive

pro

bab

ilit

y [

%]

Longer anneal improves the uniformity.


33

Effect of Furnace Anneal n+ active area (L/W=0.5/0.10mm) p+ active area (L/W=0.5/0.10mm)


Furnace anneal improves the uniformity dramatically.

0 5 10 15 20 25 30 35.01

.1

1

5102030

50

70809095

99

99.9

99.99

Hot Plate 270oC

Hot Plate 290oC

Hot Plate 350oC

Furnace 300oC

Furnace 350oC


Cum

ula

tive

pro

bab

ilit

y[%

]0 5 10 15 20 25 30 35

.01

.1

1

5102030

50

70809095

99

99.9

99.99

Hot Plate 270oC

Hot Plate 290oC

Hot Plate 350oC

Furnace 300oC

Furnace 350oC


Cum

ula

tive

pro

bab

ilit

y[%

]

34


on n+ active area by Furnace Anneal

No increase in sheet resistance at narrow line by furnace anneal.

Hot plate(Reference) (L=100mm) Furnace Anneal (L=100mm)

0

5

10

15

20

0.1 1 10

Sh

eet

Res

ista

nce

[ W

/sq

]

Width [ mm ]

Mid

Max

Min 0

5

10

15

20

0.1 1 10 S

hee

t R

esis

tan

ce [

W/s

q ]

Width [ mm ]

Med.

Max.

Min.

*Process condition

1st Anneal single 270oC

2nd Anneal 395oC

*Process condition

1st Anneal furnace 350oC

2nd Anneal 500oC

35


on p+ active area by Furnace Anneal

No increase in Sheet resistance at narrow line by furnace anneal.

0

5

10

15

20

0.1 1 10

Sh

eet

Res

ista

nce

[ W

/sq

]

Width [ mm ]

Mid

Max

Min 0

5

10

15

20

0.1 1 10 S

hee

t R

esis

tan

ce [

W/s

q ]

Width [ mm ]

Me

d.

Hot plate(Reference) (L=100mm) Furnace Anneal (L=100mm)

*Process condition

1st Anneal single 270oC

2nd Anneal 395oC

*Process condition

1st Anneal furnace 350oC

2nd Anneal 500oC

36

Comparison among Annealing tools Anneal

Tool RTA Hot Plate Furnace

Structure

Atmosphere N2 Vacuum or N2 N2

Advantage Excellent temperature

control.

•Easy for process below 300 oC.

•Available for in-situ

treatment after PVD.

・Suitable for long-term treatment.

・Suitable for low temperature treatment.

Drawback

•Unsuitable for temperature

below 300 oC.

•Unsuitable for long-term

treatment.

•Hard to control the

temperature profile.

•Unsuitable for long-term

treatment.

・Impossible for short- term treatment.

Silicide

application

Commonly used in

silicidation. ・Hardly used in silicidation.

・Hardly used in silicidation.

Furnace suitable for long and low temperature Annealing.

37

Effect of Furnace Anneal on The

Formation of High Resistivity Phases High resistivity

Phase Ni3Si2 on n type NiSi2 on p type

Example

Reaction path

2 way paths

Path1:Ni2Si→NiSi

Path2:Ni2Si→Ni3Si2→NiSi

2 way paths

Path1:Ni2Si→NiSi

Path2:NiSi2→Ni2Si→NiSi

Effect of

furnace anneal

1. Promote Ni3Si2→NiSi

reaction by large heat

quantity by long anneal.

2. Grain growth Ni2Si phase.

1. Promote NiSi2→Ni2Si reaction by

large heat quantity by long anneal.

2. Initial NiSi2 layer is not thicken (?).

*T. Isshiki et. al. 14th IEEE

International Conf. on RTP, 2006 [4.4]

*T. Isshiki et. al.

14th IEEE International

Conf. on RTP, 2006

[4.4] Ni2Si Ni3Si2

Long anneal by furnace promotes the reaction to NiSi.

38

Conclusions of Chapter 4

Furnace anneal successfully

improves the uniformity of sheet

resistance at small areas.

Increasing temperature of 1st anneal or

thickness of Ni improves the uniformity of Rs

on p+ active area only.

Increasing temperature of Ni PVD stage or

2nd anneal promotes the formation of NiSi2

phase.

39

Chapter 5 Thermal Stability of NiSi


To Investigate thermal stability of NiSi.

Clarify thermal stability difference between n+ and

p+ active areas.

Clarify thermal stability difference between NiSi on

Si(100) and Si(110).

40

Crystal Orientation and Thermal stability of NiSi

Crystal Orientation of NiSi depends on Si.

⇒Orientation of NiSi or Si changes thermal stability ?

*C. Lavoie et. al, Microelectronics Engineering 70, 144-153 (2003)

*Process condition

P type poly-Si,

Ni=15nm, 3 oC/s N2 ambient

Crystal structure of Nickel Silicide on Si(100)

*C.Detavernier et al. Nature 2003

NiSi(112) NiSi(202)/(211)

41

Thermal Stability of Sheet Resistance

0 10 20 30 40 50 60.01

.1

1

5102030

50

70809095

99

99.9

99.99

500 oC

600 oC

650 oC

700 oC


Cu

mu

lati

ve

pro

bab

ilit

y [

%]

0 10 20 30 40 50 60.01

.1

1

5102030

50

70809095

99

99.9

99.99

500 oC

600 oC

650 oC

700 oC


Cu

mu

lati

ve

pro

bab

ilit

y [

%]

n+ active area (L/W=100/10mm) p+ active area (L/W=100/10mm)

p+ active area has better thermal stability than n+ active area.

*Process condition

1st Anneal 270oC /2nd Anneal 500oC

42

Cross-sectional TEM Images of NiSi at 700oC

101 213

312

n+ active area

p+ active area

NiSi

Agglomeration of NiSi on n+ active area is confirmed.

43

20 30 40 50 60 700

100

200

300

400

2theta angle [degree]

In

ten

sit

y [

CP

S]

NiSi 200 Si 400

w/o impla.

n+-impla.

p+-impla.

20 30 40 50 60 700

100

200

300

400

2theta angle [degree]In

ten

sit

y [

CP

S]

w/o impla.

n+-impla.

p+-impla.

NiSi 020

NiSi 101

Si 220

(a) Parallel to Si (b) Parallel to Si

In-plane XRD patterns of NiSi films

NiSi (020) // Si (110) is observed on p+ implanted Si.

*Process condition

1st Anneal 270oC

2nd Anneal 500oC

44

Calculated From D. F. Wilson et al., Scripta Metal., 26, 85 (1992)

Thermal Expansion of NiSi films

R.T.

700˚C

3.00

3.50

4.00

4.50

5.00

5.50

6.00

0 100 200 300 400 500 600 700

Unit

cel

l dim

ensi

on [

nm

]

Temperature [ oC ]

a

b

c

NiSi(211)

Si(220)

NiSi(211)

Si(220) (a) Epitaxial grain

Si(220)

NiSi(020)

NiSi(202)

(b) Transrotational grain

The space of b axis decreases as temperature increases.

⇒ NiSi grains relax by arranging each grains.

*NiSi: Orthorombic axbxc=5.233x3.258x5.659

45

n+ active area (all)

n+ Ext-SD only

Deep-SD As only

Deep-SD P only

p+ active area (all)

p+ Ext-SD only

Deep-SD B only

None Dope

Annealed NiSi Images by optical microscope

NiSi on deep-SD B shows no agglomeration.

⇒Highly implanted B is the cause in high thermal stability.

*Process condition

1st Anneal 270oC

2nd Anneal 500oC

Add. Anneal 650oC

46

Effect of B dose on NiSi orientation

Si direction Si direction

NiSi (020) // Si (110) is formed at 5x1015 atoms/cm2 and above of B dose.

*H. Kimura and R. Tomita, Micro. Eng. (2010) *Process condition

1st Anneal 270oC

2nd Anneal 500oC

atoms/cm2

47

Thermal Stability Comparison

between NiSi/Si(100) and Si(110)

Process Flow

SPM 9:1

↓

BOE 20:1

↓

Ni-PVD 10nm

↓

RTA 225 to 700℃ 30sec

0

10

20

30

40

50

60

70

80

90

100

200 300 400 500 600 700Anneal Temp.[℃]

She

et R

esis

tanc

e[Ω

/sq.

]

Si(100)

Si(110)

Thermal stability: NiSi on Si(100) > Si(110).

48

In-plane XRD, f-rotation Analysis

0

500

1000

1500

2000

2500

3000

0 20 40 60 80 100 120 140 160 180

φ [℃] fromSi(110)

Inte

nsity[

coun

t]

NiSi (101)NiSi (011)NiSi (200)NiSi (111)NiSi (112)NiSi (202)/(211)NiSi (103)NiSi (301)NiSi (020)

NiSi/Si(110)

0

500

1000

1500

2000

2500

3000

0 20 40 60 80 100 120 140 160 180

φ [°] fromSi(110)

Inte

nsity[

coun

t]

NiSi (101)NiSi (011)NiSi (200)NiSi (111)NiSi (112)NiSi (202)/(211)NiSi (103)NiSi (301)NiSi (020)

NiSi/Si(100)

NiSi on both Si(100) and Si (110) align to Si substrates.

・NiSi on Si(100) is 4 fold symmetry. ・NiSi on Si(110) is 2 fold symmetry.

Strong NiSi(020)//Si(110) relation is observed from both

samples.

Si(2-20)

Si(-113) Si(1-13)

Process

Ni-PVD 10nm

RTA 500℃30sec

49

Thermal Stability of NiSi on Si (110)

NiSi on Si(110) cannot relax by contracting b-axis of NiSi because of 2 fold symmetry.

Si(220)

NiSi(020)

NiSi(202)

(a) NiSi on Si(100) Si(220)

Si(200)

NiSi(202)

NiSi(020)

(b) NiSi on Si(110) Si(220)

50


・Thermal stability of NiSi depend on crystal orientation of NiSi to Si.

・Thermal stability: NiSi on p+ > n+ active area. Highly implanted B (> 5E15atms/cm2)

⇒NiSi(020) aligns to Si(110). ⇒b-axis of NiSi contacts by increasing Temp. .

・ Thermal stability: NiSi on Si(100) > Si(110) NiSi on Si(110) cannot relax by b-axis of NiSi

because of two fold symmetry of Si(110).

51

Chapter 6 Schottky Barrier Height of

NiSi and Si Interface


Lowering Schottky barrier height of

NiSi on Si by Al.

Comparing Schottky barrier height of

NiSi on Si (100) and (110).

52

Logic CMOS Series Resistance

Series Resistance

Specific Contact Resistivity

To decrease Specific Cotact Resistivity

・Doping Density N ↑ ・Barrier Height φB ↓

*S-D Kim et al. TED2002

Schottky Barrier Height need to be reduced in order to reduce rc.

53

Schottky Barrier Height Interface State

・Dangling Bond ・Metal Induced Gap State (MIGS)

Fermi Level of Metal/Si interface

・φbp=1/3Eg

Modulation of Barrier Height

・PtSi for PFET, ErSi For NFET ・Introducing impurities at the interface.

Interface state and Fermi Level Pining

*Y-C Yeo et al. JAP2002

Semiconductor

*M.Saitoh et al. IEDM2008

CMOS on Si(110) and NiSi

*C.Detavernier et al. Nature 2003

NiSi(112) NiSi(202)/(211) CMOS Performance

Si(110) ＞ Si(100)

NiSi is affected by

Surface Orientation of Si.

Is Schottky Barrier Height on Si(110) different from Si(100) ?

54

Schottky Diode I-V Characteristic w or w/o Al

Reverse Current increases by Al.

Process Flow

1. SPM 9:1

2. SPM 4:1,HF50:1,HPM

3. Thermal SiO2 1000Å 4. Photolithography

5. SiO2 Etch, BOE 20:1

6. Resist Strip

7. Al-Implantation

1e14atm/cm2 5keV

8. HF Treatment

9. Ni-PVD 10nm

10.RTA 500℃ 30sec 11. Metal strip SPM4:1

12. Al-PVD 1000Å for back side contact

1.0E-02

1.0E-01

1.0E+00

1.0E+01

1.0E+02

-2 -1 0 1 2

I [A

/cm

2]

Voltage [V]

Si(100)

Si(100) with Al

Si(110)

Si(110) With Al

*Si(100):p-type, 10-20Ω・cm, 475-575mm *Si(110): p-type, 1-10Ω・cm, 500-550mm

55

Activation-Energy Measurements

For SBH Determination, without Al

NiSi/Si(110) NiSi/Si(100)

fBp=0.38 eV fBp=0.34 eV

fBp of Si(100) > fBp of Si(110)

⇒Charge neutral level : Si(100) > Si(110)

1.00E-14

1.00E-13

1.00E-12

1.00E-11

1.00E-10

1.00E-09

1.00E-08

3.00 3.50 4.00 4.50 5.00 5.50 6.00

I/T

2 (A

/K

2 )

Measurement Temperature 1000/T(K-1)

-0.02 V

-0.04 V

-0.06 V

-0.08 V

-0.10 V

fBp=0.38 eV

56

SIMS Profile after NiSi Formation

Al conc. of Si(110) ≈ Si(100) at NiSi/Si interface.

1E+00

1E+01

1E+02

1E+03

1E+04

1E+05

1E+06

1E+07

1E+14

1E+15

1E+16

1E+17

1E+18

1E+19

1E+20

1E+21

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

Se

co

nd

ary

ion

inte

ns

ity (c

ou

nts

/se

c)

Co

nc

en

tra

tio

n (

Ato

ms/c

m3

)

Depth (nm)

Al in Si(100)

Al in Si(110)

Si in Si100(raw ion counts)

Ni in Si100(raw ion counts)

Si in Si(110)(raw ion counts)

Ni in Si(110)(raw ion counts)

Al in Si(110)

Si(raw ion counts)->

Ni(raw ion counts)->

Al in Si(100)

57

Activation-Energy Measurements

For SBH Determination, with Al NiSi/Si(110) with Al NiSi/Si(100) with Al

fBp=0.17 eV fBp=0.23 eV

fBpof Si(100) < fBpof Si(110)

NiSi/Si(100): DfBp=0.21eV, NiSi/Si(110): DfBp=0.11eV

⇒interface states: Si(100) < Si(110)

58

In-plane XRD

No orientation change observes by Al implantation.

20 30 40 50 60 70 800

200

400

600

800

1000


In

ten

sit

y [

CP

S]

NiSi with Al-impla. on Si(100)

Si

22.5o from

Si

Si

20 30 40 50 60 70 800

200

400

600

800

1000

2theta angle[degree]

NiSi w/o Al impla. on Si(100)

Inte

nsity [C

PS

]

Si

22.5o from

Si Si

NiSi/Si(100) NiSi/Si(100) with Al

20 30 40 50 60 70 800

200

400

600

800

1000


In

ten

sit

y [

CP

S]

NiSi with Al-impla. on Si(110)

Si

Si

Si

NiSi/Si(110)

20 30 40 50 60 70 800

200

400

600

800

1000


NiSi w/o Al-impla. on Si(110)

Inte

nsity [C

PS

]

Si

Si

Si

NiSi(020)

NiSi/Si(110) with Al

59

Analysis on Schottky barrier lowering by Al

implant.

1E+00

1E+01

1E+02

1E+03

1E+04

1E+05

1E+06

1E+07

1E+14

1E+15

1E+16

1E+17

1E+18

1E+19

1E+20

1E+21

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

Se

co

nd

ary

ion

inte

ns

ity (c

ou

nts

/se

c)

Co

nc

en

tra

tio

n (

Ato

ms/c

m3

)Depth (nm)

Al in Si(100)

Al in Si(110)

Si in Si100(raw ion counts)

Ni in Si100(raw ion counts)

Si in Si(110)(raw ion counts)

Ni in Si(110)(raw ion counts)

Al in Si(110)

Si(raw ion counts)->

Ni(raw ion counts)->

Al in Si(100)

Band structure of NiSi2/Si interface

by Y addition. *Li Geng et. Al. EDL Vol.29 pp.446(2008)

Solid solubility of Al in Si is below 7x1018atms/cm3

(600℃) ⇒Accepter like Al in Si is few.

Addition of Se, S, Y, Al to NiSi/Si interface has following effects.

①Charge Neutral Level is changed by interface state change. ②Work function is changed by dipole formation.

60


Schottky Barrier Height is successfully

reduced by Al implantation for both

Si(100) and Si(110)

Barrier lowering by Al implantation is

significant for Si(100) than Si(110).

No crystal structure change of NiSi was

observed by Al implantation.

61

Conclusions of Chapter 7-1

Firstly the formation of high resistivity

phase at small area has been observed,

the issue has successfully been solved

by furnace anneal for 1st anneal.

This process has successfully been used

for a CMOS fabrication condition.

62

Conclusions of Chapter 7-2 Chapter 3

The formation of Ni3Si2 or NiSi2 at small areas is

confirmed.

⇒The formation of Ni3Si2 or NiSi2 is related to complex Ni-Si phase diagram and reaction mechanisms.

Chapter 4

Modifying silicide condition for improve the uniformity of

sheet resistance at small area.

⇒Furnace anneal for 1st anneal dramatically improves the uniformity.

63

Conclusions of Chapter 7-3 Chapter 5 Thermal stability: NiSi on p+ > n+ active area.

⇒NiSi(020) aligns to Si(110) on p+ active area. ⇒b-axis of NiSi contacts by increasing Temp. .

Thermal stability: NiSi on Si(100) > Si(110)

⇒ NiSi on Si(110) cannot relax by b-axis of NiSi. Because of Two folds symmetry of Si(110).

Chapter 6 Schottky Barrier Height is successfully reduced by Al

implantation for both Si(100) and Si(110)

Barrier lowering by Al is significant for Si(100) than Si(110).

Academic Paper & Presentation

タイトル年月日雑誌・学会名著者

Formation of High Resistivity Phases

of Nickel Silicide at small Diffusion Region 2007年6月

International Workshop

on Junction Technology

R.Tomita, H. Kimura,

M. Yasuda, T. Nakayama,

K. Maeda, Y. Sugiyama,

Y. Kikuchi, M. Moritoki

Analysis and Improvement

on the Uniformity of

Sheet Resistance of Nickel Silicide

2008年5月 International Workshop

on Junction Technology

R.Tomita, M. Yasuda,

H. Kimura, K. Maeda,

S. Ueno, M. Moritoki

微小領域におけるニッケルシリサイドの層抵抗均一性とその改善方法

2008年6月

応用物理学会

シリコンテクノロジー分科会

第102回研究集会

R.Tomita, H. Kimura,

M. Yasuda, K. Maeda,

S. Ueno, M. Moritoki

Formation of High Resistivity Phases

of Nickel Silicide at Small Area accepted

Microelectronics

Reliability

R. Tomita, H. Kimura,


S. Ueno, T. Tomizawa,

Y. Kunimune, H. Nakamura,

M. Moritoki, H. Iwai

Improvement on Sheet Resistance

Uniformity of Nickel Silicide

by Optimization of Silicidation Conditions

accepted Microelectronics

Reliability

R. Tomita, H. Kimura,


S. Ueno, T. Tonegawa,

T. Fujimoto, M. Moritoki,

H. Iwai

A Study on Formation of High Resistivity Phases of …...Resistivity [mW・cm] C54:13~20, C49:80~100...

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Transcript of A Study on Formation of High Resistivity Phases of …...Resistivity [mW・cm] C54:13~20, C49:80~100...