Table Of ContentSpringer Series in
MATERIALS SCIENCE 24
Springer-Verlag Berlin Heidelberg GmbH
Physics and AstronOmy9:J
O.U.EU. ....
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Springer Series in
MATERIALS SCIENCE
Series Editors: R. Hull . R. M. Osgood, Ir. . H. Sakaki . A. Zunger
The Springer Series in Materials Science covers the complete spectrum of materials physics,
including fundamental principles, physical properties, materials theory and design. Recognizing
the increasing importance of materials science in future device technologies, the book tides in this
series reflect the state-of-the-art in understanding and controlling the structure and properties
of all important classes of materials.
31 Nanostructures and Quantum Effects 36 Ceramics
By H. Sakaki and H. Noge Mechanical Properties, Failure
Behaviour, Materials Selection
32 Nitride Semiconductors and Devices By D. Munz and T. Fett
ByH.Morko~
37 Technology and Applications
33 Supercarbon of Amorphous Silicon
Synthesis, Properties and Applications
Editor: R. A. Street
Editors: S. Yoshimura and R. P. H. Chang
38 Fullerene Polymers
34 . Computational Materials Design and Fullerene Polymer Composites
Editor: T. Saito
Editors: P. C. Eklund and A. M. Rao
35 Macromolecular Science 39 Semiconducting Silicides
and Engineering
Editor: V. E. Borisenko
New Aspects
Editor: Y. Tanabe 40 Reference Materials
in Analytical Chemistry:
A Guide for Selection and Use
Editor: A. Zschunke
Series homepage - http://www.springer.de/phys/books/ssms
Volumes 1-30 are listed at the end of the book.
Klaus Graff
Metallmpurities
in Silicon-Device
Fabrication
Second, Revised Edition
With 47 Figures
Springer
Dr. Klaus Graff
Telefunken Electronic Present Address:
Theresienstrasse 2 Hegelmaierstrasse 46
74072 Heilbronn, Germany 74076 Heilbronn, Germany
Series Editors:
Prof. Rohert Hull Prof. H. Sakaki
University ofVirginia Institute ofIndustrial Science
Dept. of Materials Science and Engineering University ofTokyo
Thornton Hall 7-22-1 Roppongi, Minato-ku
Charlottesville, VA 22903-2442, USA Tokyo 106, Japan
prof. R. M. Osgood, Jr. Prof. Alex Zunger
Microe1ectronics Science Laboratory NREL
Department ofElectrical Engineering National Renewable Energy Laboratory
Columbia University 1617 Cole Boulevard
Seeley W. Mudd Building Golden Colorado 80401-3393, USA
New York, NY 10027, USA
Library of Congress Cataloging-in-Publication Data.
Graff, Klaus, 1931-
Metal impurities in silicon-device fabrication I Klaus Graff.--2nd, rev. ed
p. cm. --(Springer series in materials science; 24)
Includes bibliographical references and index.
ISBN 978-3-642-62965-5 ISBN 978-3-642-57121-3 (eBook)
DOI 10.1007/978-3-642-57121-3
1. Semiconductors--Defects. 2. Silicon--Inclusions. 3. Silicon--Defects. 4.
Contamination (Technology) I. Title. 11. Springer series in materials science ; v. 24.
TK7871.852.G]3 1999
621.3815'2--dC21 99-058100
ISSN 0933-033X
ISBN 978-3-642-62965-5
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Preface
At the end of the first edition of this monograph it was mentioned that the
current data should be corrected and completed within reasonable periods
of time. Although this period was rather short, the time has come to prepare
a second edition with additional and more recent results taken from almost
100 selected papers that appeared in the meantime. In addition to a large
number of minor corrections, further details and comments have been
added.
Two main advances in knowledge and understanding have enabled us
to solve problems, on the one hand, and fill blanks, on the other hand. They
are
(i) the detection and investigation of several hydrogen complexes that form
during the etching of silicon samples and can considerably deteriorate the
detection of the characteristic deep energy levels of the impurity to be in
vestigated by means of DLTS. Only avoiding the formation of hydrogen
complexes by avoiding etching enables one to record the true DLT spectra,
for example, of palladium and platinum. Both exhibit three deep energy
levels which formerly could not be clearly detected or identified because of
the reduced concentrations.
(ii) The investigation of many rare 4d and 5d transition metals by DLTS
measurements performed after the growth of contaminated crystals. The
new results fill almost all blanks and hence enabled a systematic overview
of the behaviour of transition metals in silicon. A large number of these
transition metals can hardly be diffused into silicon because of their high
reactivity with the ambient atmosphere or their extremely low diffusivity
and solubility. As a consequence of the filled blanks a conspicuous similar
ity between the electrical properties of the metals within one group of equal
number N of s plus d electrons could be observed. This led to the tentative
conclusion that the boundary between stable interstitial and substitutional
defects might be located between the groups of N = 8 and N = 9. However,
this assumption has been proven only for the 3d metals.
New data are presented in Chap.5 in the sequence of the 3d, 4d, and
5d transition metals. In addition, all tables have been revised with respect to
recently published data. Identified complexes of the corresponding metal
are also included in the tables. The electrical properties of all metals and
v
complexes presented in the text are summarized in two appendices at the
end of the text, one in alphabetic order of the chemical symbols and the
other in numeric order of their actication energies.
In conclusion, we have tried to make this monograph even more suit
able as a reference for scientists and engineers working in laboratories or at
their desks. For convenience, we have summarized in the listing to follow
the symbols used throught the text and, in particular, in the tables.
I am deeply grateful to Prof. J. Weber, Max-Planck Institute in Stutt
gart (FRG) for providing me with several preprints and selected suitable
recent literature and to Prof. W. Schr6ter and Dr. M. Seibt, University of
G6ttingen, who spent extended time discussing various problems and re
viewing collected data. I am also grateful to Dr. H. Lemke, Technical Uni
versity of Berlin, for private telephone communications and for preprints. I
am obliged to many colleagues, meeting regularly in workshops on point
defects in silicon at the Max-Planck Institute in Stuttgart, for presenting
their recent results and sending me preprints. In addition I want to thank
my editor Dr. H.K.V. Lotsch, Springer-Verlag, Heidelberg, for giving me
the opportunity to revise this monograph. Finally, I thank my wife Ursula
for her patience during the frequent absence of her husband.
Heilbronn
August 1999 Klaus Graff
VI
Preface to the First Edition
This monograph deals with the physical principles and properties of transi
tion-metal impurities dissolved or precipitated in mono crystalline silicon. It
is intended as an introduction to the important field of defect engineering,
which is of growing interest for the fabrication of modern electronic de
vices. On the other hand, it is intended as a reference for scientists and eng
ineers actively involved in silicon device research and development, in re
search institutes and industrial laboratories. It is assumed that the reader al
ready has a basic understanding of the physics of silicon and of the tech
nological processing of silicon wafers in present device fabrication.
Since the well-known investigations performed by G.W. Ludwig and
H.H. Woodbury in the early 60's, our knowledge of the behaviour of metal
impurities in silicon, on contamination sources, their impact on device per
formance, and on detection facilities has increased tremendously. Although
this development has not yet ceased, the multitude of highly specialized
publications which appeared in the last decades calls for a critical review of
the manifold details. The present monograph provides a survey of the basic
physical processes which lead to contamination, dissolution, diffusion and
precipitation of metal impurities in silicon. It also gives an overview of
modern analytical facilities and specific data on the properties of transition
metals in silicon as far as they are known to date. Finally, gettering phe
nomena are discussed since they are directly coupled to the presence of un
wanted metal impurities. So far, gettering remains an indispensible tech
nological process in modern fabrication techniques. It is hoped that this
monograph can serve as a basis for a better understanding of the sophisti
cated reactions observed in silicon samples contaminated with metal impuri
ties, and taking place during the multitude of technological processes which
are required for manufacturing electronic devices.
I am deeply grateful to many of my former colleagues at TEMIC and
other scientific and industrial laboratories in central Europe. First of all I
am obliged to my former supervisors Drs. G. Goldbach and D. Wolff for
giving me the opportunity to write this monograph alongside my engage
ment in defect engineering, and ingot and process control at TEMIC Heil
bronn, FRG. In addition, I want to thank H. Pieper for numerous discus
sions and ideas for solving problems in measurement and preparation tech-
VII
niques and for his technical assistance over many years. I am grateful to
Mrs. C. Huger and Miss P. Heim for preparing numerous samples and
making measurements which enabled most of our own results to be
obtained. I want to thank D. Wallis for drawing all the figures and Mrs. A.
Muller for performing the photographic work. In addition, thanks are ex
pressed to all colleagues met during many workshops on "Point Defects in
Silicon" initiated by Profs. E. Sirtl and J. Schneider in 1979. Since then
these workshops have taken place twice a year at the Max-Planck Institute
in Stuttgart/FRG under the guidance of Prof. H.-J. Queisser. These meet
ings were always a source of useful information and a possibility to become
acquainted with experts from the industrial and university laboratories of
central Europe, their methods and their most recent results. Finally, I am
obliged to Dr. M. Seibt, University of G6ttingen for critically reading this
manuscript and for providing me with the TEM micrographs from precipi
tates of the main impurities in silicon. In addition, he suggested many cor
rections and improvements, as well as additional references. Last but not
least, I especially thank my wife Ursula for her understanding that writing
and its subsequent corrections require much time and patience.
Heilbronn
June 1994 Klaus Graff
VIII
Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 1
2. Common Properties of Transition Metals. . . . . . . . . . . . .. 5
2.1 General Behavior ............................ 5
2.2 Contamination of Silicon Wafers. . . . . . . . . . . . . . . . . . . 9
2.2.1 Solid Phase . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.2 Liquid Phase . . . . . . . . . . . . . . . . . . . . . . . ... . 1. 0
2.2.3 Vapor Phase . . . . . . . . . . . . . . . . . . . . . . . . . . .. 12
2.3 Impact on Device Performance. . . . . . . . . . . . . . . . . . . .. 14
2.3.1 Dissolved Transition Metals ................... 15
2.3.2 Precipitated Transition Metals . . . . . . . . . . . . . . .. 18
3. Properties of Transition Metals in Silicon. . . . . . . . . . . . .. 20
3.1 Solubilities ....................... . . . . . . . .. 21
3.2 Diffusivities ............................... 25
3.3 Dissolved Impurities . . . . . . . . . . . . . . . . . . . . . . . . .. 30
3.3.1 Point Defects. . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.3.2 Complexes ............................. 42
3.4 Precipitated Metals . . . . . . . . . . . . . . .. . .......... 51
3.4.1 Volume Precipitates ........................ 52
3.4.2 Surface Precipitates -Haze ................... 58
3.4.3 Haze Phenomena .......... . . . . . . .. 63
4. Properties of the Main Impurities . . . . . . . . . . . . . . . . . .76 .
4.1 Iron ...................................... 77
4.1.1 Solubility . . . . . . . . . . . . . . . . . . . . . . 7. 7 . . . . . . .
4.1.2 Diffusivity ................... . . . . . . . 78
4.1.3 Behavior During Heat Treatment. . . . . . . . . . . . . . . . 79
4.1.4 Electrical Activity. . . . . . . . . . . . . . . . . . . . . . . . . 80
4.1.5 Properties of the Precipitates . . . . . . . . . . . . . . . . .. 86
4.1.6 Known Impurity Sources, and Common Concentrations . 87
4.1.7 Avoidance of Contamination .................. 88
4.2 Nickel . . . . . . . . . . . . . . . . . . .. ........... 89
4.2.1 Solubility .............................. 90
4.2.2 Diffusivity ............................. 91
4.2.3 Behavior During Heat Treatment. . . .. . ......... 92
4.2.4 Electrical Activity. . . . . . . . . . . . . . . . . . . . . . 93
4.2.5 Properties of the Precipitates. . . . . . . . . . . . . . . . . . 95
IX
4.2.6 Known Impurity Sources, and Common Concentrations . 96
4.2.7 Avoidance of Contamination .................. 97
4.3 Copper. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
4.3.1 Solubility .............................. 99
4.3.2 Diffusivity ..... . . . . . . . . . . . . . . . . . . . . . . . . 99
4.3.3 Behavior During Heat Treatment. . . . . . . . . . . . . .. 100
4.3.4 Electrical Activity. . . . . . . . . . . . . . . . . . . . . . .. 101
4.3.5 Properties of the Precipitates. . . . . . . . . . . . . . . .. 103
4.3.6 Known Impurity Sources and Common Concentrations. 104
4.3.7 Avoidance of Contamination . . . . . . . . . . . . . . . .. 105
4.4 Molybdenum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 106
4.4.1 Solubility . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 107
4.4.2 Diffusivity ................ . . . . . . . . . . .. 107
4.4.3 Behavior During Heat Treatment. . . . . . . . . . . 108
4.4.4 Electrical Activity. . . . . . . . . . . . . . . . . . . . . . .. 108
4.4.5 Properties of the Precipitates. . . . . . . . . . . . . . . .. 108
4.4.6 Known Impurity Sources and Common Concentrations. 108
4.4.7 Avoidance of Contamination . . . . . . . . . . . . . . . .. 109
4.5 Palladium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 109
4.5.1 Solubility .. . . . . . . . . . . . . . . . . . . . . . . . . . .. 110
4.5.2 Diffusivity ..... . . . . . . . . . . . . . . . . . . . . . .. 111
4.5.3 Behavior During Heat Treatment. . . . . . . . . . . . . .. 112
4.5.4 Electrical Activity. . . . . . . . . . . . . . . . . . . . . . .. 113
4.5.5 Properties of the Precipitates. . . . . . . . . . . . . . . .. 115
4.5.6 Known Impurity Sources and Common Concentrations. 117
4.6 Platinum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 117
4.6.1 Solubility .. . . . . . . . . . . . . . . . . . . . . . . . . . .. 118
4.6.2 Diffusivity .... . . . . . . . . . . . . . . . . . . . . . . .. 119
4.6.3 Behavior During Heat Treatment. . . . . . . . . . . . .. . 120
4.6.4 Electrical Activity. . . . . . . . . . . . . . . . . . . . . . .. 121
4.6.5 Properties of the Precipitates. . . . . . . . . . . . . . . .. 123
4.6.6 Known Impurity Sources and Common Concentrations. 123
4.6.7 Avoidance of Contamination . . . . . . . . . . . . . . . .. 123
4.7 Gold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 124
4.7.1 Solubility . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 125
4.7.2 Diffusivity ...... . . . . . . . . . . . . . . . . . . . . .. 125
4.7.3 Behavior During Heat Treatment. . . . . . . . . . . . . .. 126
4.7.4 Electrical Activity. . . . . . . . . . . . . . . . . . .. .1 2.7 . .
4.7.5 Properties of the Precipitates . . . . . . . . . . . . . . .. 129
4.7.6 Known Impurity Sources and Common Concentrations 129
4.7. 7 Avoidance of Contamination. . . . . . . . . . . . . . . .. 130
x
