Properties of Aluminum Oxide and Aluminum Oxide Alloys and their Interfaces with Silicon and ...

104 Pages·2002·1.59 MB·English

Abstract
ROBERT SHAWN JOHNSON. Properties of Aluminum Oxide and Aluminum
Oxide Alloys and their Interfaces with Silicon and Silicon Dioxide. (Under the
direction of Gerald Lucovsky.)

A remote plasma enhanced chemical vapor deposition method, RPECVD,
was utilized to deposit thin films of aluminum oxide, tantalum oxide, tantalum
aluminates, and hafnium aluminates. These films were analyzed using auger
electron spectroscopy, AES, Fourier transform infrared spectroscopy, FTIR, X-
ray diffraction, XRD, nuclear resonance profiling, NRP, capacitance versus
voltage, C-V, and current versus voltage, J-V.
FTIR indicated the alloys were homogeneous and pseudobinary in
character. Combined with XRD the crystallization temperatures for films >100 nm
were measured. The alloys displayed an increased temperature stability with the
crystallization points being raise by >100ºC above the end point values.
In-situ AES analysis provided a study of the initial formation of the films'
interface with the silicon substrate. For Al O these results were correlated to
2 3
NRP results and indicated a thin, ~0.6 nm, interfacial layer formed during
deposition.
C-V characteristics indicated a layer of fixed negative charge associated
with Al O . For Ta O the C-V and J-V results displayed high levels of leakage
2 3 2 5
current, due to a low conduction band offset with silicon. Both aluminates were
dominated by electron trapping states. These states were determined to be due
to (i) a network "break-up" component and (ii) localized atomic d-states of
hafnium and tantalum atoms.
PROPERTIES OF ALUMINUM OXIDE AND ALUMINUM OXIDE ALLOYS AND
THEIR INTERFACES WITH SILICON AND SILICON DIOXIDE

by
ROBERT SHAWN JOHNSON

A dissertation submitted to the Graduate Faculty of
North Carolina State University
in partial fulfillment of the
requirements for the Degree of
Doctor of Philosophy

PHYSICS

Raleigh, North Carolina
2001
Biography
Robert Shawn Johnson was born in Saranac Lake, NY on April 1st, 1974.
He attended the AuSable Valley Central School system and received his high
school diploma in June of 1992. From there he enrolled in the State University of
New York College at Geneseo. He majored in physics with a minor in
mathematics. While at Geneseo he contributed the operation and maintenance of
a 2 MeV Vande Graff accelerator, on which he performed Rutherford
backscattering experiments. He received his Bachelor of Arts in Physics in May
of 1996.
After graduating he moved to Raleigh, NC where he attended North
Carolina State University. At NC State he studied Physics and worked as a
research assistant for Dr. Gerald Lucovsky. While under the direction of Dr.
Lucovsky he studied replacement materials for silicon dioxide in CMOS
applications. In December of 2001, he received his Ph.D. from NC State.
ii
Acknowledgements
I would like to thank all the members of my committee, Dr. Aspnes, Dr.
Lucovsky, Dr. Misra, and Dr. Parsons, for their insightful views and comments
during my tenure at NC State.
Thank you to my advisor, Dr. Lucovsky, whose experience and guidance
has provided a wonderful path to this degree. In addition to his knowledge in the
field of semiconductors, I would like to thank him for his in-sights into the subtle
area of life.
To the members of the Lucovsky research group, Dr. Doug Stephens, Dr.,
Bruce Hinds, Dr. Dave Wolfe, Dr. Fuchao Wang, Dr. Kwangok Koh, Dr. Hanyang
Yang, Dr. Yider Wu, Dr. Bruce Claflin, Brian Solazo, Dr. Hiroaki Niimi, Bruce
Rayner, Dr. Robert Therrien, Dr. Donghun Kang, Michael Schultz, Klaus Flock,
Yi-Mu Lee, Choelhwyi Bae, Joon Goo Hong and Christopher Hinkle, it has been
an interesting and enjoyable experience. Thank you all for the many times you
placed your research to the side and aided in mine.
I am grateful to all the members of the cleanroom. Thank you for all the
hours you spent trying to educate me in the ways of device processing.
Finally, I would like to thank my family. Especially my wife, Christine, and
daughter, Irene, two best reasons to complete this degree and move forward.
And a big thank you to the New York fan base, the Johnson's and the Phillips'
(sometimes called the Case's).
iii
Table of Contents
Page
LIST OF TABLES. vi
LIST OF FIGURES. vii
1 INTRODUCTION. 1
1.1 The Need for High Dielectric Constant Materials. 1
1.2 General Properties of High Dielectric Constant
Materials. 2
1.3 Objective. 4
1.4 Overview of the Dissertation. 4
1.5 References. 6
2 EXPERIMENTAL METHODS. 11
2.1 Materials Deposition. 11
2.1.1 Remote Plasma Enchanced Chemical Vapor
Deposition, RPECVD. 11
2.1.2 Metal Organic Bubbler. 12
2.2 Auger Electron Spectroscopy, AES. 13
2.3 Nuclear Resonance Profiling, NRP. 14
2.4 Fourier Transform Infrared Spectroscopy, FTIR. 15
2.5 X-Ray Diffraction, XRD. 15
2.6 Electrical Characterization - Capacitance and
Current versus Voltage, C-V and J-V. 16
2.7 References. 17
3 PROPERTIES OF RPECVD ALUMINUM OXIDE. 21
3.1 Introduction. 21
3.2 Interface with silicon and silicon dioxide. 22
3.3 Bulk properties, FTIR and XRD. 24
3.4 Electrical Characterization. 25
3.5 Conclusions. 30
3.6 References. 31
iv
Page
4 PROPERTIES OF RPECVD TANTALUM OXIDE. 45
4.1 Introduction. 45
4.2 Interfacial Formation on HF-Last Silicon and
Preoxidized Silicon. 45
4.3 FTIR Results. 47
4.4 Electrical Characterization. 47
4.5 Conclusions. 49
4.6 References. 50
5 PROPERTIES OF TANTALUM AND HAFNIUM
ALUMINATES. 59
5.1 Introduction. 59
5.2 Bulk Composition and Properties by AES, RBS, and
FTIR. 60
5.3 Interface Formation by AES. 61
5.4 Electrical Characterization. 62
5.5 Discussion. 64
5.6 Conclusions. 69
5.7 References. 71
6 SUMMARY AND FUTURE WORK. 91
6.1 Aluminum and Tantalum Oxide. 91
6.1.1 Aluminum Oxide, Al O . 91
2 3
6.1.2 Tantalum Oxide, Ta O . 92
2 5
6.2 Tantalum and Hafnium Aluminates. 92
6.3 Future Work. 93
v
List Of Tables
Page
Table 1.1 Local electronic and physical properties of selected
high-k materials. 8
Table 2.1 Remote plasma process conditions. 18
vi
List Of Figures
Page
Figure 1.1 General molecular orbital diagram for oxides of
transition metals. 9
Figure 1.2 Plot of oxygen coordination as a function of average
bond ionicity, I . 10
b
Figure 2.1 RPECVD glas flow and bubbler assembly for all
depositions. 19
Figure 2.2 RPECVD chamber for depositions. 20
Figure 3.1 AES of aluminum oxide deposition on HF-last silicon
and 0.6nm of silicon dioxide on HF-last silicon. 33
Figure 3.2 NRP for Al O on HF-last silicon. 34
2 3
Figure 3.3 NRP for Al O on 2.2nm of silicon dioxide deposited
2 3
on HF-last silicon. 35
Figure 3.4 FTIR for >100nm of aluminum oxide on silicon before
and after a 900ºC anneal. 36
Figure 3.5 X-Ray Diffraction, XRD, for aluminum oxide on
Si(100). 37
Figure 3.6 C-V data for aluminum oxide on HF-last silicon. 38
Figure 3.7 Flatband voltage for Al O on HF-last silicon as a
2 3
function of the aluminum oxide EOT. 39
Figure 3.8 Flatband voltage for stacked Al O and SiO
2 3 2
MOSCAP’s as a function of the aluminum oxide EOT. 40
Figure 3.9 Leakage current density versus V -V . 41
G FB
Figure 3.10 Ideal band bending for n- and p-MOS devices. 42
Figure 3.11 Temperature Dependence of C-V for n-MOS Al O
2 3
and SiO . 43
2
vii
Page
Figure 3.12 Temperature dependence of J-V for Al O on HF-last
2 3
silicon. 44
Figure 4.1 AES of tantalum oxide deposition on HF-last silicon
and 0.6nm of silicon dioxide on HF-last silicon. 52
Figure 4.2 FTIR for >100nm of tantalum oxide on silicon before
and after an 800°C anneal. 53
Figure 4.3 Room temperature C-V for Ta O on pre-oxidized
2 5
silicon. 54
Figure 4.4 1 MHz Temperature Dependence C-V for n-MOS
Ta O and SiO . 55
2 5 2
Figure 4.5 J-V for Ta O on pre-oxidized silicon. 56
2 5
Figure 4.6 Temperature dependence of J-V for Ta O on
2 5
pre-oxidized silicon. 57
Figure 4.7 J vs. 1/T for n-MOS Ta O device at V -V = 0.4 V. 58
2 5 G FB
Figure 5.1 Differential AES spectra for the Al O -Ta O alloy
2 3 2 5
system. 73
Figure 5.2 Fourier transform infrared spectroscopy, FTIR, for as-
deposited Ta-aluminates and their end-members,
Al O and Ta O . 74
2 3 2 5
Figure 5.3 FTIR spectra of crystalline Al O -Ta O alloy films. 75
2 3 2 5
Figure 5.4 Fourier transform infrared spectroscopy, FTIR, for as-
deposited Hf-aluminates and their end-members,
Al O and HfO . 76
2 3 2
Figure 5.5 FTIR spectra of crystalline Al O -HfO alloy films. 77
2 3 2
Figure 5.6 RBS compositional calibration of AES signal levels of
Al-O and Ta-O peaks. 78
Figure 5.7 RBS compositional calibration of AES signal levels of
Al-O and Hf-O peaks. 79
viii
Page
Figure 5.8 AES of interface formation for x=0.43,
(Ta O ) (Al O ) . 80
2 5 x 2 3 (1-x)
Figure 5.9 AES of the initial stages of deposition
of Hf-aluminates. 81
Figure 5.10. Room temperature, 1 Mhz, C-V plots for Al O , Ta O ,
2 3 2 5
and Ta-aluminates on (a) p-silicon and (b) n-silicon
with aluminum gates. 82
Figure 5.11. Room temperature, 1 Mhz, C-V plots for Al O , HfO ,
2 3 2
and Hf-aluminates on (a) p-silicon and (b) n-silicon
with aluminum gates. 83
Figure 5.12. Temperature dependent C-V for SiO , Al O , Ta O ,
2 2 3 2 5
and HfO on p-silicon with aluminum gates. 84
2
Figure 5.13. Temperature dependence of (a) C-V and (b) J-V for
43% Ta O Ta-aluminate on p-silicon with aluminum
2 5
gates. 85
Figure 5.14. Temperature dependence of (a) C-V and (b) J-V for
38% HfO Hf-aluminate on p-silicon with aluminum
2
gates. 86
Figure 5.15. Temperature dependence of (a) C-V and (b) J-V for
48% HfO Hf-aluminate on n-silicon with aluminum
2
gates. 87
Figure 5.16. J vs. 1/T for 43% Ta O Ta-aluminate on p-silicon. 88
2 5
Figure 5.17. J vs. 1/T for both 38% and 48% HfO Hf-aluminates
2
on p- and n-silicon, respectively. 89
Figure 5.18. Localized bonding, b., and anti-bonding, a.b.*,
states in Ta- and Hf-aluminates. 90
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