1

Surface reactions and interface evolution during the ALD of HfO2 on GaAs surfaces

studied by in situ ATR-FTIR

Liwang Ye, Theodosia Gougousi

Department of Physics University of Maryland, Baltimore County (UMBC),

Baltimore, MD 21250

University of Maryland, Baltimore County

2 University of Maryland, Baltimore County

Motivation

Atomic layer deposition (ALD) of high-κ on III-V has promising applications in MOSFET.

Poor quality native oxides are detrimental to MOSFET applications.

Interface self-cleaning has been widely observed.1

1. P. D. Ye et al. APL 83, 180 (2003), M. M. Frank et al. APL 86, 152904 (2005), D. Shahrjerdi et al. APL 92, 223501 (2008), L. Huang et al. APL 87, 252104 (2005), C.-H. Chang et al. APL 89, 242911 (2006),C. L. Hinkle et al. APL 92, 071901 (2008), Hackley et al. APL 92(16), 162902 (2008) , Suri et al. APL 96, 112905 (2010).

Gougousi et al. TSF 518, 2006 (2010)Gougousi et al. JES, 157(5), H551 (2010)

III-V semiconductor

Metal oxideNative oxide

III-V semiconductor

Before ALD After ALD

ALD

Motivation: understanding the “interface self-cleaning”

3

(1) Ligand exchange 3 HfL4 + 2 A2O3 → 3 HfO2 + 4 AL3L

(2) Precursor decomposition

N

CH 3

CH3

(3) Oxide conversion 4 GaAs + 3 As2O5 → 2 Ga2O3 + 3 As2O3 + 4 As

GaAsNative oxide

M

L

L L

L

GaAsNative oxide

DecompositionByproducts

M: Metal atom

L

N

CH 3

CH3

A= As or Ga or In

S. Klejna and S. D. Elliott, Chem. Mater. 26, 2427 (2014).

C. H. Chang et al. APL 89, 242911 (2006).

R. P. Vasquez et al. APL 42, 293 (1983).

University of Maryland, Baltimore County

4

Internal reflection element (IRE) (GaAs)

IR detector

IR source

Rotary vane pump

H2O

 

TDMAH FTIR Attenuated total reflection (ATR) cell

Pressure gauge

N2

In situ ATR-FTIR setup

.

Computer

  

D2O/H2

18O 

Fixed volume

University of Maryland, Baltimore County

K. Li et al., JVSTA 25, 1389 (2007), K. Li et al., JPCC 114, 14061 (2010).

5

• Precursor: TDMAH and H2O

Experimental details: ALD process

University of Maryland, Baltimore County

1st T

DM

AH

1st H

2O

Time (min)0 3 4 5

N2 p

urge

and

sp

ectra

take

n1st Cycle

2nd CycleRea

ctor

pr

essu

re

N2 p

urge

and

sp

ectra

take

n

1 2

HfN

CH3

CH3

N

CH 3

CH3

N CH3

CH3

N

CH3

CH3

[Hf(N(CH3)2)4]

TDMAH

6

Abs

orba

nce

4000 3000 2000 1000

Wavenumber (cm-1)

2920& 2851

1630

1067

843

As-OH2O

CH

0.01

Abs

orba

nce

1000 700

Wavenumber (cm-1)

1067

843

As-O

0.01

Characterization of the GaAs starting surface

GaAs

Native oxide

GaAs

chemical oxide

Chemical oxide GaAs(100)

Native oxide GaAs(100)

Reference of the spectra are the HF etched GaAs surface. As-O region

University of Maryland, Baltimore County

M. Rei Vilar et al. Surf. Interface Anal. 37, 673 (2005).

Abs

orba

nce

4000 3500 3000 2500 2000 1500 1000

Wavenumber (cm-1)

147

0 1

410

157

2

277

7 2

855

363

0

324

0

8600.002

1st TDMAH

2nd H2O

20th TDMAH

20th H2O

1st H2O

2nd TDMAH

120

0 1

046

7

ALD of HfO2/CO GaAs(100) at 275°C

GaAs

chemical oxide

HfN(CH3)2(CH3)2N

H

O

H

O

HfN(CH3)2(CH3)2N

(CH3)2N N(CH3)2

CH3 stretch

OH

H

TDMAH

OH

H

chemical oxide

HfO2HfO2

CH3 -N=CH

2 (MMI)

Hf-OH

As-O removal

University of Maryland, Baltimore County

8

1200 1100 1000 900 800

HfO2/CO GaAs HfO2/HF GaAs

0.003

1 cycle

2 cycles

3 cycles

10 cycles

20 cycles

Interface self-cleaning during the ALD of HfO2 at 275 °C

The references for these spectra are their respective starting surfaces.

0.5

0.4

0.3

0.2

0.1

0.0

Are

a of

rem

oved

As-

O

20181614121086420

No. of cycles

As-O region As oxide removal during the deposition at 275 °C

Gradual removal of the arsenic oxide has been observed during the deposition

L. Ye and T. Gougousi, APL, 105, 121604 (2014).

Removed As-O

III-V semiconductor

HfO2chemical oxide

GaAs

ALD

University of Maryland, Baltimore County

Abs

orba

nce

Wavenumber (cm-1)

9

Interface self-cleaning during the ALD of HfO2 at 275°CA

bsor

banc

e

Wavenumber (cm-1)

The references for these spectra are their respective starting surfaces.

As-O region

L. Ye and T. Gougousi, APL, 105, 121604 (2014).

As-O-HfL : N(CH3)2

HfL

L L

L

As-O-As AsOHfL

L L

AsL

+

HfL

L L

L

As AsOHfL

L L H-L +

OH

(1)

(2)

Two possible reaction schemes.

University of Maryland, Baltimore County

1200 1100 1000 900 800

HfO2/CO GaAs HfO2/HF GaAs

0.003

1 cyc

2 cyc

3 cyc

10 cyc

20 cyc 1046

10

Effect of the deposition temperature on the interface self-cleaning

Abs

orba

nce

1200 1100 1000 900 800

Wavenumber (cm-1)

275 °C

200 °C

0.003 100 °C

250 °C

20 cycles of HfO2 ALD on “CO GaAs” (100) surface. The spectra have been referenced to the respective starting surfaces.

The arsenic oxide removal is enhanced at higher deposition temperatures.

Deposition temperature

Removed As oxides

Suri et al. APL 96, 112905 (2010).

University of Maryland, Baltimore County

11

1500 1000

860

0.002

157

2 1

470

141

0

104

6

Abs

orba

nce

Wavenumber (cm-1)

Interface self-cleaning during the ALD of HfO2 at 275 °C

HfO2/CO GaAsCH3-N=CH2

(MMI)

TDM

AH TD

MA

H TDM

AHTD

MA

HH 2O H 2O H 2O H 2O

0.20

0.15

0.10

0.05

0.00Pe

ak a

rea

20151050 Time (mins)

CH Stretch 1572 cm-1

University of Maryland, Baltimore County

1st TDMAH

2nd TDMAH1st H2O

2nd H2O3rd H2O

10th H2O

20th H2O

The reference for these spectra is the starting surface.

12

Possible reaction schemes for the production of MMI

Hf

N(C

H3) 2

N(C

H3) 2

+ OH

H2

Hf

OH

OH

+ HN(CH3)22(a)

Hf

OH

OH+ HN(CH3)2 + + H2N=CH2CH3 -

(b)

Hf

OH

OH

+ + HHN=CH2CH3-2 2(c)

Surface reaction schemes at H2O half cycle during the ALD of HO2 on GaAs surfaces.

University of Maryland, Baltimore County

J. P. A. M. Driessen et al. J. Electrochem. Soc., 148, G178 (2001),S. Salim et al. Chem. Mater. 7, 507 (1995).

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Continuous removal of arsenic oxide during the first 20 ALD cycles has been observed.

Temperature dependence of the arsenic oxide removal has been confirmed.

Methylmethyleneimine (MMI) is produced during the H2O exposure and accumulates in the film.

Conclusions

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