oral presenation avs 2013 liwang 10-25-13

1

Surface Reactions During ALD of TiO2 on GaAs Surfaces Studied by

in situ ATR-FTIR

Liwang Ye, Theodosia Gougousi

Department of Physics, University of Maryland, Baltimore County, Baltimore, MD 21250

University of Maryland, Baltimore County

2 University of Maryland, Baltimore County

Motivation

ALD of high k on III-V has promising applications on MOSFET.

Poor native oxides are the main difficulties for the applications.

Interface self-cleaning has been widely discovered.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)

3

Si

TiO2Ti

N(CH3)C2H5(CH3)C2H5N

(CH3)C2H5N N(CH3)C2H5

TEMAT

B. Kan et al., J. Phys. Chem. A 113(16), 3946 (2009).

M. Bouman et al., ECS Transactions, 33 (2) 291-305 (2010).

Si

HfO2

TDMAH HfN(CH3)(CH3)N

(CH3)N N(CH3)

K. Li et al., J. Phys. Chem. C 114, 14061 (2010).

Y. Wang et al., and T. Gustafsson, Chem. Mater. 2007, 19, 3127-3138 3127.

K. Li et al., J. Phys. Chem. C 2011, 115, 18560–18571.

HfN(CH3)C2H5(CH3)C2H5N

(CH3)C2H5N N(CH3)C2H5

HfN(C2H5)2(C2H5)2N

(C2H5)2N N(C2H5)2

TEMAH

TDEAH M. J. Kelly et al., Chem. Mater. 2005, 17, 5305-5314.

In situ FTIR study of high k ALD on Si


4

To detector IR incidence IRE (GaAs)

IR detector

IR source

Pump

H2O

TDMAT FTIR ATR cell

Pressure gauge

N2

K. Li, S. Li, N. Li, D. A. Dixon, and T. M. Klein, J. Phys. Chem. C 114, 14061 (2010).

Experiment details: in situ ATR-FTIR setup


~12 total reflections on top surface

5

• Precursor: TDMAT and H2O 1st

TDM

AT

1st H

2O

Time (min)0 3 4 5 6 7

Pum

p an

d ta

ke sp

ectr

a

Pum

p an

d ta

ke sp

ectr

a

1st Cycle

2nd CycleReac

tor

pres

sure

Note: Y-axis only serves as a guide for understanding the procedure.

Ti

N(CH3)2(CH3)2N

(CH3)2N N(CH3)2

TDMAT

Experimental details: ALD process


6

GaAs surface preparation


Abs

orba

nce

4000 3000 2000 1000

Wavenumber (cm-1)

CO GaAs F GaAs

H2O

C-H H2O

As-O

As-O

As-O or Ga-O

free OH

“F GaAs” surface: etched in BOE

“CO GaAs” surface:“F GaAs” soaked in (30%)H2O2 at 45°C for 10~30mins.

GaAs

chemical oxide

TiO2

~3nmReference: native oxide GaAs

Reference: F GaAs

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

Abs

orba

nce

4000 3500 3000 2500 2000 1500 1000

Wavenumber (cm-1)

TiO2 / CO GaAs 100C

1st TDMAT

1st H2O

2nd TDMAT

2nd H2O

20th TDMAT

20th H2O

1598 14

6614

09

0.004

7

CH3 stretching from TDMAT

ALD of TiO2/CO GaAs(100) at 100°C


NC2 stretching from TDMAT

TiO2

8

60x10-3

40

20

0

Inte

grat

ed p

eak

area

20151050 Time(mins)

0.400.300.200.100.00

20151050

Peak areas vs deposition time

1st TD

MA

T

2nd TD

MA

T

3rd TD

MA

T

1st H

2O

2nd H

2O

3rd H

2O

CH stretching

1598 cm-1

IncreaseDecrease

ALD of TiO2/CO GaAs(100) at 100°C


9

Possible assignments of the 1598 cm-1: H-O-H bending mode of H2O. OCO stretching of formate (HCOO) . OCO stretching of carbonate (HCO3). N-H bending mode of methylamine (CH3NH2). C=N stretching of Methylmethyleneimine

(CH3N=CH2) (MMI).

Discussion: the possible assignments


10

D2O H218O D2O

Or H218O

Species Liquid H2OMMA

CH3NH2 on TiO2

Formate HCOO

Bidentate carbonateHOCOOTi

MMI(CH3N=CH2)

Modes Scissoring NH2 scissoring

Anti. Sym. OCO

stretchingOCO Sym. stretching

N=C stretching

Peak (cm-1) ~1620 1607 1607 1582 ~1590

Peak with isotope

D2O CH3ND2 HC18O18O H18OC18O18O CH3N=CH2

~1200 1205 1587 1570 ~1590

Shift (cm-1) 400 ~400 20 ~12 0

ReferencesR. Nakamura, et al.

Langmuir 17, 2298(2001)

Li. –F. Liao et al. J. Phys. Chem. B 105,

5928(2001).

L.-F. Liao et al., J. Phys. Chem. B, 106(43), 11241

(2002).

L.-F. Liao et al., J. Phys. Chem. B, 106(43), 11241

(2002).

C. M. Truong et al. J. Phys. Chem. 99,

8831(1995).

Isotope exchange experiments


11

Abs

orba

nce

4000 3500 3000 2500 2000 1500 1000

Wavenumber (cm-1)

1598 14

6614

09

10 cyc of TiO2 on CO GaAs 100C

ALD with H216O

ALD with H218O

0.001

• D2O exchange excludes the assignments of H2O and CH3NH2.• H2

18O exchange experiment excludes the possibilities of formate and carbonate species.

Abs

orba

nce

4000 3500 3000 2500 2000 1500 1000

Wavenumber (cm-1)

1598

1466

1409

10 cyc of TiO2 on CO GaAs 100C

2400

ALD with D216O

ALD with H216O

0.001

Isotope exchange experiments


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OHHO O

TiN

(CH

3) 2

N(C

H3) 2

+ N=CH2CH3-

+ O OTi

O-HO-H HN(CH3)2

O OTi

N(C

H3) 2

N(C

H3) 2

-N(CH3)2 + HN=CH2CH3- + H2

O OTi

O-HO-H

+O OTi

N(C

H3) 2

N(C

H3) 2

+

HN(CH3)2

Mechanism ?

2 -N(CH3)2+N=CH2CH3-

+

Ref. 2

1. J. P. A. M. Driessen et al., J. Electrochem. Society, 148(3), G178(2001).2. S. Salim et al., Chem. Mater. 7, 507(1995).

((CH3)2N)xE + H ((CH3)2N)x-1E + H2 + H2C=NCH3 E: As, P, Sb; x=1,2,3

Ref. 1+H2 2 + H2

Reaction scheme


OHH

OHH

13

OHHO O

TiN

(CH

3) 2

N(C

H3) 2

+ N=CH2CH3-

+O OTi

O-HO-H

HN(CH3)2

O OTi

N(C

H3) 2

N(C

H3) 2

-N(CH3)2 + HN=CH2CH3- + H2

O OTi

O-HO-H

+O OTi

N(C

H3) 2

N(C

H3) 2

+

HN(CH3)2

Mechanism ?

2 -N(CH3)2+ N=CH2CH3-+

Ref. 2

1. J. P. A. M. Driessen et al., J. Electrochem. Society, 148(3), G178(2001).2. S. Salim et al., Chem. Mater. 7, 507(1995).

((CH3)2N)xE + H ((CH3)2N)x-1E + H2 + H2C=NCH3 E: As, P, Sb; x=1,2,3

Ref. 1

+H2 2 + H2

Reaction scheme for revison


OHH

OHH

14

Effect of ALD temperature and surface preparation


Abs

orba

nce

4000 3500 3000 2500 2000 1500 1000 Wavenumber (cm-1)

20 cyc of TiO2 on GaAs

CO GaAs 100 C

CO GaAs 200 C

1598

1466

1409

0.002

F GaAs100 C

F GaAs 200 C

Abs

orba

nce

4000 3500 3000 2500 2000 1500 1000

Wavenumber (cm-1)

1st TDMAH

2nd TDMAH

30th TDMAH

1st H2O

2nd H2O

30th H2O

ALD HfO2/CO GaAs at 275C Reference: CO GaAs 1

598

146

6 1

409

0.004

• The spectrum of 30 cycles of HfO2 resembles the one from ALD of TiO2 on GaAs. A broad negative peak is growing at As-O region.

15

ALD HfO2/CO GaAs

University of Maryland, Baltimore CountyA

bsor

banc

e

1200 1100 1000 900 800

Wavenumber (cm-1)

0.004

As-O region

16

As oxide removal was observed during the deposition at 275°C but was not observed at 200°C.

GaAs oxide removal


Abs

orba

nce

1400 1300 1200 1100 1000 900 800

Wavenumber (cm-1)

As-O

B: As-prepared CO GaAs (RT)

A: After 30cyc HfO2 cooled down to RT

As-O

A-B: Difference of two spectra

0.01

ALD HfO2/CO GaAs at 275C Reference: etched GaAs surface

17

For the deposition of TiO2 on GaAs surface, Methylmethyleneimine (MMI) was produced during the H2O exposure and accumulates in the film.

As oxide removal was observed during the deposition on HfO2 on chemical oxide GaAs surface at 275°C but was insignificant at 200°C.

Conclusions


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Acknowledgements


DMR-0846445

Alex Henagar

oral presenation avs 2013 liwang 10-25-13

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