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Advantages of Hard X-ray Photoelectron Spectroscopy (HAXPES) in the Characterization of

Advanced Semiconductor films.

Giuseppina ContiApplied Materials Inc., Santa Clara, CA

Christian Papp, Chuck Fadley,LBNL, Berkely, CA

2

G_Conti BNL May 21,2009

Outline:

– High-k/Metal gate: Entire film stack physical characterization (thickness, composition, depth profile and chemical state).

– Soft x-ray XPS fails to provide depth profile and chemical state information of the entire film stack.

– Hard-X ray XPS using a synchrotron beam at Sping8 provides non-destructive depth profile and chemical state.

Can the entire gate stack layers be investigated without sample manipulation ?

3


Metal Oxide Silicon (MOS) Transistor

Gate

Source Drain

Base

Oxide

carrierschannel

Provides control for on/off state

Insulating gate electrode from channel

Provides carriers for channel conduction

Drains away channel current

Allows S/D connection

Provides substrate bias

20ÅHfOx/SiO2

100Å TiN

Poly-SiT>500Å

4


Experiment: Sample description

~100 Å

Si wafer: substrate

SiO2

HfO2

TiN

Cap layer: poly-Si

Si wafer: substrate

SiO2

HfO2

TiN

Cap layer: poly-Si

Si wafer: substrate

SiO2

HfO2

TiN

Cap layer: poly-Si~50 Å

~20 Å

~8 Å

TiN/highKinterfaceinfluences the Vt shift

Highk/SiO2 interface influences the mobility & leakage current

This sample was annealed at T=1000°C

5


Soft X-ray XPS depth profile : Ar sputtering

TiNHfO2

Hf4f at the TiN – HfO2 interface Hf4f at the HfO2 – SiO2 interface

Is this Hf0

HfN, or an artifacts??

HfO2

SiO2/Si

O-Hf

Problems: 1) Is Ar sputtering changing the material chemical state?2) Is Ar sputtering increasing the surface roughness?

Problems: 1) Is Ar sputtering changing the material chemical state?2) Is Ar sputtering increasing the surface roughness?

fHf-O

012 14 16 18 20 22 24

BE(eV)

ALD HfO2 before TiN deposition

Hf4f

6


Soft X-ray : AR-XPS after Ar sputtering

SiO2HfO2

TiN about 30-40A

Si wafer sub.

Log[(IXi (θ0 )/IXi (θn)]]

surface

Qualitative depth atom distribution

substrate

SiO2HfO2

TiN

Si wafer sub.

High Roughness

SiO2 Film thickness

7


1st Conclusion:

The combination of Ar sputtering and AR-XPS analysis fails to provide a chemical characterization of the entire stack layer of about 150A.

The use of Ar sputtering introduces artifacts such as ion mixing and differential sputtering.

The surface after partial Ar sputtering is so rough ( roughness by AFM data increases of more than 1 order of magnitude) that AR-XPS is compromised.

So…..

8


Hard X-ray photoemission

AR-XPS Data at ∼6 keV were collected atSPring8

Feasibility Study of HK-MG stack by

9


350 450 550 650BE(eV)

Hf4p3

N1s

Hf4p2

Ti2pO1s

Ti2s

350 450 550 650BE(eV)

Hf4p3

N1s

Hf4p2

Ti2pO1s

Ti2s

00 100 200 300BE(eV)

coun

ts

Hf4f

Si2p

Si2s

Hf4d

C1s

Ti3s

Ti3p

00 100 200 300BE(eV)

coun

ts

Hf4f

Si2p

Si2s

Hf4d

C1s

Ti3s

Ti3p

Hard X-ray ( X-ray Energy=6000eV) : survey spectrum

☺Hf is detected without any sample manipulation

or sample sputtering

10


Angle Resolved Hard X-ray data

n

θ

0

3000

6000

9000

0 50 100 150 200 250

BE(eV)

AU

theta_10_cos Theta_30-cos Hf_theta50_cosTheta 70 cos Theta 88 cos

Si2s

Si2p

Ti

Ti

Hf4f

hard-Xray

0

1000

2000

3000

4000

5000

6000

7000

8000

200 300 400 500 600BE(ev)

Cou

nts

Hf_11_88_costHf_12_70_costHf_13_50_costHf_14_30_costHf_10_10_cost

C1s Hf2p3

N1s

Ti2pO1s

Ti2s

hard-Xray

0

1000

2000

3000

4000

5000

6000

7000

8000

200 300 400 500 600BE(ev)

Cou

nts

Hf_11_88_costHf_12_70_costHf_13_50_costHf_14_30_costHf_10_10_cost

C1s Hf2p3

N1s

Ti2pO1s

Ti2s

C1s Hf2p3

N1s

Ti2pO1s

Ti2s

sample

Θ = 10°(top film surface)Θ = 88°(bulk film)

11


Sample:1 Si sub/8A SiO2/20A HfO2/100A/TiN/50A/ poly-Si

SESSA

Si wafer: substrate

SiO2

HfO2

TiN

Cap layer: poly-Si~50Å

~100Å

~20Å

~8 Å

12


Experimental data of angle resolved XPS hard-X-ray are fitted by Sessa Simulation

Hf 4f

010 20 30 40 50 60 70 80 90

take-off angles

AU

Hf4f_data Sessasim

Hf4f

film surface Film bulk

HfO2

Ti

2010 20 30 40 50 60 70 80 90

take off angle

AU

Ti2S dataSessa Sim. Int.

Si wafer: substrate

SiO2

HfO2

TiN

Cap layer: poly-Si

◊ Experimental data : Area of Hf4f and Ti2s

Sessa simulation: Area of Hf4f and Ti2s of the simulated spectra

13


Conclusions:

•Hard X-ray AR-XPS shows the following advantages in comparison with traditional AR-XPS and Ar sputtering XPS :

•Surface and bulk information are obtained without sample manipulation

•The interface at TiN/HfO2 layer is observed and the dielectric layer consists of HfOx.

( from previous presentation at LBNL October workshop on Hard X-ray)

14


Recent data analysis Chemical State Information as a function of depth

-4

1

Si2s C1s O1s N1s Ti2p Hf4p3

Relative depth plot experimental data Top surface

Bulk

))

(

)(

ln(

8830

°°

xI

xI

The intensity of SiO2 and Si° at the bottom of the film stack are too weak to be discriminated from the top Si layer

HfTiNCOSix

where

;;;;;≡

15


X-ray = 6KeVData analysis : Si2pSi2p spin/orbit splitting.

400

600

800

1000

1200

5830 5840 5850

Cou

nts

/ s (

Res

id. ×

1)

Kinetic Energy (eV)

angle=70

Si2p3

Si2p1

So2pO

1000

1500

2000

2500

3000

5835 5840 5845 5850

Cou

nts

/ s (

Res

id. ×

1)

Kinetic Energy (eV)

theta=50

Si2p3

Si2p1Si2pO

500

1000

1500

5835 5840 5845 5850

Cou

nts

/ s (

Res

id. ×

1)

Kinetic Energy (eV)

angle=30

Si2p3

Si2 p1Si2pO

Spectral resolution ~0.47eV for all the take-off angles.

16


Experimental data : O1s

0

1000

2000

3000

4000

5000

6000

7000

525528531534537540

BE(eV)

coun

ts/s

ec

t=88 T=70 t=50 t=30

O1s

O-Si O-Me

Realtive % O-Me

0

5

10

15

20

25

30

35

40

45

50

29 34 39 44 49 54 59 64 69 74 79 84 89

angles

%O

-Me

O1s

0102030405060708090

100

29 39 49 59 69 79 89

angles

rela

tive

%

O1s-Si O1s-Met

O-Si

O-Me

Topsurface

Si-O TiN O HfOx

3.00E+04

4.00E+04

5.00E+04

6.00E+04

7.00E+04

5408 5410 5412 5414 5416 5418 5420

Cou

nts

/ s (

Res

id. ×

2)

Kinetic Energy (eV)

angle=88

O1s-Me

O1s-Si

17


0

2000

4000

6000

8000

10000

12000

450455460465

BE(eV)

coun

ts/s

ec

t=88 ( /10) T=70 t=50 t=30

0

2000

4000

6000

8000

10000

12000

14000

16000

394396398400402

BE(eV)

coun

ts/s

ec

t=88 ( /10) T=70 t=50 t=30

Ti2pN1s

Experimental data: Ti2p and N1s

N1s BE is constant for all the angle .

0.00E+00

2.00E+04

4.00E+04

6.00E+04

8.00E+04

5475 5480 5485 5490 5495 5500

Cou

nts

/ s (

Res

id. ×

2)

Kinetic Energy (eV)

angle=88angle=88 A

angle=88 B angle=88 C

angle=88 D

an gle=8 8 E

18


Ti2p comparison with reference samples:1) TiN; TiOx

1000450 455 460 465 470

TiN TiO Angle=88

TiN_ref.

TiOx_ ref

Sample at θ=88

TiN

TiOx x>1

TiO

XPS International data base

19


Experimental data: Hf4f

7012 14 16 18 20 22 24

BE(eV)

angle=88 angle=70 angle=50 angle=30

013 14 15 16 17 18 19 20 21 22 23

BE(eV)

AU

HfON HXray XPS HfO2

Comparison: references: HfO2 and HfON

HfO2

Angle=88

HfO2 ref.

HfON ref.

20


Hf4f peak fitting

200

400

600

800

1000

1200

1400

1600

1800

5922 5924 5926 5928 5930 5932 5934

Cou

nts

/ s (

Res

id. ×

1)

Kinetic Energy (eV)

angle=88

Hf4f7N

Hf4fNO

Hf4f7O

Hf4f5O

Hf4f5N

))

(

)(

ln(

8830

°°

xI

xI

HfN HfNO HfO2

TiN interface

Substrate

21


SiO2 15 Å

TiNO 20 Å

TiN 77Å

10 Å diffusion

Si 25.5 Å

Si substrate

MoSi2 4.5 Å

MoSi2 4.5 Å

Si 25.5 Å

2 Å diffusion

69 X

MoSi2 4.5 ÅSi 18 Å

2.15

2.10

2.05

2.00

1.95

1.90

Inci

denc

e A

ngle

[deg

.]

470 465 460 455 450Binding Energy [eV]

Inte

nsity

[arb

. u.]

534 532 530 528

Binding Energy [eV]

O 1s oxygen 1 oxygen 2

Inte

nsity

[arb

. u.]

470 465 460 455 450Binding Energy [eV]

Ti 2p Ti oxydized Ti and Ti satellite

2.20

2.15

2.10

2.05

2.00

1.95

1.90

Inci

denc

e A

ngle

[deg

.]

534 532 530 528Binding Energy [eV]

Standing wave : 100A TiN/ native SiO2/ MoSix mirror

Christian Papp at al.;See poster

TiN:• without cap layer• not annealed

22


Suggested stack layer structure by H-AR-XPS and by standing wave

analysis

Summary

HfON 19Å

SiO2 16 Å

Poly-Si ~30Å

HfO2Si substrate

TiNO 80Å

Ti

2010 20 30 40 50 60 70 80 90

take off angle

AU

Ti2S dataSessa Sim. Int.

TiN-Hf interface

TEM

Si substrate

HfOx

TiN

Film stack was annealed at T=1000C for mimicking Gate First device

23


Conclusions:

•The chemical characterization of Si, O, Ti and Hf shows that our film does not have sharp interfaces between each layer.

•The presence on O in the TiN layer could explain the higher than expected resistivity.

•The intermixing of TiN with HfO2 explains the large leakage current of this sample.

•For the first time the diffusion of N into the HfO2 layer has been demonstrated.

•The intermixing layer of N-Hf-O is about 19Å

•This work shows that HAXPES, including standing wave excitation, is a powerful technique providing useful information for advanced semiconductor film development.

•Collaborations between industry and universities may greatly help in developing advanced devices.

24


Gate

Source Drain

Base

Oxide

carrierschannel

20ÅHfOx/SiO2

100Å TiN

Poly-SiT>500Å

1. Metal gate characterization: New films under investigations.

2. High K dielectric with K > HfO2 and EOT < HfO2 .

3. Ultra shallow junction As and B dopants distribution and chemical state

Outlook : HAXPES applications

Si based- Photovoltaic cells: 1. AZO characterization: Zn-O atomic distribution. Where is Al?

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