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Thermally oxidized SiO 2 formation on 4H-SiC substrate by considering the 4H SiC substrate by considering the interface reaction kinetics Shun Nakatsubo, Tomonori Nishimura, Koji Kita, Shun Nakatsubo, Tomonori Nishimura, Koji Kita, Kosuke

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SLIDE 1

Thermally oxidized SiO2 formation on 4H-SiC substrate by considering the 4H SiC substrate by considering the interface reaction kinetics

Shun Nakatsubo, Tomonori Nishimura, Koji Kita, Shun Nakatsubo, Tomonori Nishimura, Koji Kita, Kosuke Nagashio and Akira Toriumi Department of Materials Engineering Department of Materials Engineering The University of Tokyo 7-3-1 Hongo, Tokyo 113-8656, Japan This work was partly presented at SSDM 2011 (Nagoya).

2012/1/30 IEEE EDS MQ WMNACT31 (TIT) 1

p y p ( g y )

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SLIDE 2

Outline Outline

1 Background and Objective 1.Background and Objective 2 Sample Preparation

  • 2. Sample Preparation

3 Experimental Results

  • 3. Experimental Results

4 Discussion

  • 4. Discussion

5 Conclusion

  • 5. Conclusion

2012/1/30 IEEE EDS MQ WMNACT31 (TIT) 2

slide-3
SLIDE 3

Effective WF vs. Vacuum WF

Ge Si

eV) Vacuum level

Ge

▲n-type

Si

▼p-type ▲n type

V) Vacuum level 4 CB unction (e

M

▲n-type

4 unction (e

S = 0.02

CB

S=0.27

W

Ti

Sc Zr

CNL ve work fu

Er Y

Al Ni

Mg

Yb Er Zr CNL ve work fu Pt Y Al Ni Au Sc La Hf Ti

S 0.02

VB 3 4 5 6 5

W

VB Effectiv Pt Al Au

CNL 4.58eV

3 4 5 6 5 Effectiv 3 4 5 6 Vacuum work function m (eV) 3 4 5 6 Vacuumwork function m (eV)

2012/1/30 IEEE EDS MQ WMNACT31 (TIT) 3

slide-4
SLIDE 4

Interface Science of SiC

1) (S     

S M B

Schottky Barrier

1

B

S   

M

S   

Ge Si SiC Ge Si SiC

2012/1/30 IEEE EDS MQ WMNACT31 (TIT) 4

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SLIDE 5

Si Oxidation

Bt t 2 A X

A 2 2

2 

       2

B 4 A

 

O2 O2 SiO2

 

   t A B X

Si Si Deal‐Grove Model

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Deal Grove Model

slide-6
SLIDE 6

Objective

To demonstrate high quality SiO2/SiC interface i h l id i f SiC in thermal oxidation process of SiC

SiO

SiC

in O2

SiC

SiO2

SiC SiC

2012/1/30 IEEE EDS MQ WMNACT31 (TIT) 6

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SLIDE 7

Outline Outline

1 Background and Objective

  • 1. Background and Objective

2 Sample Preparation 2.Sample Preparation 3 Experimental Results

  • 3. Experimental Results

4 Discussion

  • 4. Discussion

5 Conclusion

  • 5. Conclusion

2012/1/30 IEEE EDS MQ WMNACT31 (TIT) 7

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SLIDE 8

Kinetic Consideration of SiC Oxidation

1000

T (゜C)

1200 1100 1000 900 800

Deal & Grove, JAP 36 (1965)3770.

  • ur)

Si (Deal & Grove)

, ( )

100

  • (nm/h

C-face

10

Si-face

/A ratio

  • T. Yamamoto et al., JJAP 47 (2008)7803.

0.7 0.8 0.9 1.0 1

B/

Because oxidation process is reaction‐limited,

1000/T (1/K)

2012/1/30 IEEE EDS MQ WMNACT31 (TIT) 8

its rate is Si > C‐face SiC >> Si‐face SiC.

slide-9
SLIDE 9

Kinetic Consideration of SiC Oxidation

O2 O2 SiO O2 O2 COn

2

Si

SiO2 SiO2

COn

SiO2

Si SiC SiC SiC

Reaction No Reaction

1200ºC 800ºC

2012/1/30 IEEE EDS MQ WMNACT31 (TIT) 9

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SLIDE 10

APL 70 (1997) 2280 APL 70 (1997) 2280. A uniform oxidation on nonplanar SiC Si 70 nm by depositing Si prior to SiC oxidation

SiC

Si 70 nm

SiC

Si Oxidation at 1050ºC in Wet O Si Oxidation at 1050 C in Wet O2

Oxidation of deposited thick Si on SiC in high temperature also causes oxidation of SiC.

2012/1/30 IEEE EDS MQ WMNACT31 (TIT) 10

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SLIDE 11

Sample Preparation

Wafers Si and C face 4H SiC Si d iti (~3 ) Main process flow 5~6m epi layer N‐dope ~1E16cm‐3 Si‐ and C‐face 4H‐SiC Si deposition(~3 nm) Thermal oxidation / 800゜C, dry O2

5, 15, 50 min

k lli i ( i) Back metallization (Ni) PMA / 940゜C, N2, 5 min HfO2 deposition(~10 nm)

HfO

PDA / 500゜C, 0.1% O2, 30 sec Au electrode

Si SiO2 HfO2 NiSix

4H-SiC

NiSix

2012/1/30 IEEE EDS MQ WMNACT31 (TIT) 11

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SLIDE 12

Why HfO2 ?

10

1x10-10 8x10-11

HfO2/SiO2/Si

C (F)

1 kH

6x10-11

10

1 kHz 10 kHz 100 kHz

1x10-10 8x10-11

  • 2
  • 1

1 2 V (V)

1 MHz

Vg (V)

No frequency dispersion nor hysteresis

2012/1/30 IEEE EDS MQ WMNACT31 (TIT) 12

No frequency dispersion, nor hysteresis

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SLIDE 13

Outline Outline

1 Background and Objective

  • 1. Background and Objective

2 Sample Preparation

  • 2. Sample Preparation

3.Experimental Results 3.Experimental Results 4 Discussion

  • 4. Discussion

5 Conclusion

  • 5. Conclusion

2012/1/30 IEEE EDS MQ WMNACT31 (TIT) 13

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SLIDE 14

Comparison betw een Si-face and C-face SiC O id ti R t

Oxidized at 800ºC

  • Oxidation Rate -

1

︶

Oxidized at 800ºC O2

8

e s s ︵ n m

  • n

C

  • f

a c e S i C

Si

SiO2

6

  • n

S i

  • f

a c e S i C

O

2

T h i c k n

Si SiC SiC

1 2 3 4 5

S i O O x i d a t i

  • n

T i m e ︵ m i n ︶

Si‐C: 0.189 nm Si O 0 162 nm

SiC

Si‐O: 0.162 nm

Just a monolayer SiO2 if any.

  • Fig. 3

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Just a monolayer SiO2 if any.

slide-15
SLIDE 15

Comparison betw een Si-face and C-face SiC Bi di ti l C V Ch t i ti

  • Bi-directional C-V Characteristics -

Si‐face C‐face

4 x 1

  • 7

5 x 1

  • 7

1 M H z

3 x 1

  • 7

4 x 1

  • 7

1 M H z

2 x 1

  • 7

3 x 1

  • 7

︵ F / c m

2

︶

1 K H z 1 K H z 1 K H z

2 x 1

  • 7

3 x 1

︵ F / c m

2

︶

1 K H z 1 K H z 1 K H z

1 x 1

  • 7

2 x 1 C 1 x 1

  • 7

C

  • 2
  • 1

1 2 3 4 V g ︵ V ︶

  • 2

2 4 6 8 1

V g ︵ V ︶

Dry oxidation at 800ºC for 50 min

Ideal VFB

Dry oxidation at 800ºC for 50 min

On Si‐face, there are little frequency dependence and hysteresis,

2012/1/30 IEEE EDS MQ WMNACT31 (TIT) 15

and VFB is close to the ideal value.

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SLIDE 16

Outline Outline

1 Background and Objective

  • 1. Background and Objective

2 Sample Preparation

  • 2. Sample Preparation

3 Experimental Results

  • 3. Experimental Results

4.Discussion 4.Discussion 5 Conclusion

  • 5. Conclusion

2012/1/30 IEEE EDS MQ WMNACT31 (TIT) 16

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SLIDE 17

A big difference betw een Si-face and C-face SiC

1

This work

8

s ︵ n m ︶

  • n

C

  • f

a c e S i C

6

  • n

S i

  • f

a c e S i C

T h i c k n e s s

  • T. Yamamoto et al., JJAP 47 (2008)7803.

1 2 3 4 5 6

S i O

2

O x i d a t i

  • n

T i m e ︵ m i n ︶

  • T. Yamamoto et al., JJAP 47 (2008)7803.

Although oxidation rate is significantly different, a same amount of C should be introduced into O x i d a t i

  • n

T i m e ︵ m i n ︶ On Si‐face, no carbon will be introduced Into SiO2, because of negligible oxidation of Si‐face SiC. a given thickness of SiO2. g g

We can make a carbon‐free SiO2 on Si‐face SiC

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by low temperature oxidation of Si/SiC.

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SLIDE 18

Conclusion and Future Outlook

  • Good C V characteristics in SiC MOS capacitors have been demonstrated
  • Good C‐V characteristics in SiC MOS capacitors have been demonstrated

simply by oxidation in dry O2 at 800ºC, on the basis of thermodynamic and kinetic consideration.

  • High‐k dielectric films will be applicable for SiC gate stacks by using stable

interfacial SiO2 layer.

  • SiC interface research is old but will be a hot topic.
  • Si‐face is much better than C‐face due to a considerably lower oxidation

rate in the present method.

  • MOSFET fabrication and characterization will be the next challenge.

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