Fundamentals of Electrochemical Deposition, Second Edition

374 Pages·2006·5.524 MB·English

by  Milan Paunovic, Mordechay Schlesinger(auth.)

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FUNDAMENTALS OF
ELECTROCHEMICAL
DEPOSITION
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A complete list of the titles in this series appears at the end of this volume.
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FUNDAMENTALS OF
ELECTROCHEMICAL
DEPOSITION
SECOND EDITION
MILAN PAUNOVIC
Formerly with IBM Research Division
Yorktown Heights, NY
MORDECHAY SCHLESINGER
University of Windsor
Windsor, Ontario, Canada
A JOHN WILEY & SONS, INC., PUBLICATION
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Copyright © 2006 by John Wiley & Sons, Inc. All rights reserved
Published by John Wiley & Sons, Inc., Hoboken, New Jersey
Published simultaneously in Canada
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Library of Congress Cataloging-in-Publication Data:
Paunovic, Milan.
Fundamentals of electrochemical deposition / Milan Paunovic, Mordechay
Schlesinger. — 2nd ed.
p. cm.
Includes bibliographical references and index.
ISBN-13: 978-0-471-71221-3
ISBN-10: 0-471-71221-3
1. Electroplating. I. Schlesinger, Mordechay. II. Title.
TS6 70.P29 2006
671.7(cid:1)32—dc22
2005058421
Printed in the United States of America
10 9 8 7 6 5 4 3 2 1
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CONTENTS
Preface to the Second Edition vii
Preface to the First Edition ix
1. Overview 1
2. Water and Ionic Solutions 7
3. Metals and Metal Surfaces 25
4. Metal–Solution Interphase 41
5. Equilibrium Electrode Potential 55
6. Kinetics and Mechanism of Electrodeposition 77
7. Nucleation and Growth Models 113
8. Electroless Deposition 139
9. Displacement Deposition 169
10. Effect of Additives 177
11. Electrodeposition of Alloys 199
12. Metal Deposit and Current Distribution 209
13. Characterization of Metallic Surfaces and Thin Films 221
14. In Situ Characterization of Deposition 237
15. Mathematical Modeling in Electrochemistry 249
16. Structure and Properties of Deposits 273
17. Electrodeposited Multilayers 289
18. Interdiffusion in Thin Films 307
19. Applications in Semiconductor Technology 321
20. Applications in the Fields of Magnetism and Microelectronics 333
21. Frontiers in Applications: The Field of Medicine 345
Index 355
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PREFACE TO THE
SECOND EDITION
The first edition of this book was published some eight years ago. During this period
of time, a number of new significant developments have taken place in the field of
electrochemical deposition. It is this progress that makes the second edition desirable
and indeed, necessary.
Specifically, in this edition we have made updatesto most chapters. We have also
added three new chaptersdealing with important applications of electrochemical dep-
osition in the areas of semiconductor technology (Chapter 19), magnetism and micro-
electronics (Chapter 20), and medicine (Chapter 21). In Chapter 19 we describe
development of electrodeposition of copper interconnects on chips as one major
advance in microelectronics. In Chapter 20, applications relevant to magnetic infor-
mation/data storage are highlighted. In Chapter 21 we discuss applications relating to
issues of electrochemical deposition of medical devices, highlighting surface electro-
chemistry. In this context it is noted that in the last decade or so, a number of first-tier
universities have been introducing courses dealing with electrochemical deposition
and its many practical applications.
Last, but not least, we have added problemsfor the benefit of those who intend to
use this book as a text in an appropriate university course at the graduate or senior
undergraduate level.
We are indebted to a number of people, probably too many to be mentioned, with
one exception. M.S. thanks his wife, Sarah, for always being there, and M.P. thanks
his grandchildren, Nicole, Alexander, Daniel, and Isabel, for constant encouragement.
MILANPAUNOVIC
Port Washington, New York
MORDECHAYSCHLESINGER
Windsor, Ontario, Canada
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PREFACE TO THE
FIRST EDITION
Electrochemical deposition has, over recent decades, evolved from an art to an exact
science. This development is seen as responsible for the ever-increasing number and
widening types of applications of this branch of practical science and engineering.
Some of the technological areas in which means and methods of electrochemical
deposition constitute an essential component are all aspects of electronics—macro
and micro, optics, optoelectronics, and sensors of most types, to name only a few. In
addition, a number of key industries, such as the automobile industry, adopt the
methods even when other methods, such as evaporation, sputtering, chemical vapor
deposition (CVD), and the like, are an option. That is so for reasons of economy
and/or convenience.
By way of illustration, it should be noted that modern electrodeposition equips the
practitioner with the ability to predesign the properties of surfaces, and in the case of
electroforming, those of the whole part. Furthermore, the ability to deposit multilay-
ers of thicknesses in the nanometer region, via electrochemical methods, represents
yet a new avenue of producing new materials.
This book, whose title and subject matter are fundamental to the science of electro-
chemical deposition, is intended for readers who are newcomers to the field as well as to
those practitioners who wish to broaden and sharpen their skills in using this technology.
It may be considered a fortunate coincidence that this book is published at the
time of the introduction of copper interconnection technology in the microelectron-
ics industry. In 1998 the major electronic manufacturers of integrated circuits (ICs)
are switching from aluminum conductors produced by physical methods (evapora-
tion) to copper conductors manufactured by electrochemical methods (electrodepo-
sition). This revolutionary change from physical to electrochemical techniques in the
production of microconductors on silicon is bound to generate an increased interest
and an urgent need for familiarity with the fundamentals of electrochemical deposi-
tion. This book should be of great help in this crucial time.
The book is divided into 18 chapters, presented in a logical and practical order as
follows. After a brief introduction (Chapter 1) comes the discussion of ionic solu-
tions (Chapter 2), followed by the subjects of metal surfaces (Chapter 3) and metal
solution interphases (Chapter 4). Electrode potential, deposition kinetics, and thin-
film nucleation are the themes of the next three chapters (5–7). Next come electroless
and displacement-type depositions (Chapter 8 and 9), followed by the chapters dealing
with the effects of additives and the science and technology of alloy deposition
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x PREFACE TO THE FIRST EDITION
(Chapters 10 and 11). Current distribution during deposition and both in situ and
ex situ deposit characterization are the focus of Chapters 12–14. Electronic design
(mathematical modeling) is the subject of Chapter 15, followed by the issues of
structure, properties of deposits, multilayers, and interdiffusion (Chapters 16–18).
Each chapter is self-contained and independent of the other chapters; thus the
chapters do not have to be read in consecutive order or as a continuum, and readers
who are familiar with the material in certain chapters may skip those chapters and
still derive maximum benefit from the chapters they read.
As the title page indicates, the two of us, the authors, come from different and at
the same time complementing environments. One of us (M.P.) has been with indus-
try and the other (M.S.), with academia for most of our respective carriers. This gave
rise to the unique style and flavor of the book hereby presented to the reader.
To sum up, this book may and should be viewed as either a textbook for advanced
science and engineering students, a reference book for the practitioners of deposition,
or as a resource book for the science-minded individuals who desire to familiarize
themselves with a modern, exciting, and ever-evolving field of practical knowledge.
It is a pleasure to gratefully acknowledge the professional help and support of the
staff at John Wiley & Sons.
Finally, we would like to express our heartfelt gratitude to many individuals in
The Electrochemical Society and in particular to members of the Electrodeposition
Division as well as to our respective families for support and encouragement.
MILANPAUNOVIC
Yorktown Heights, New York
MORDECHAYSCHLESINGER
Windsor, Ontario, Canada
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1
Overview
1.1. INTRODUCTION
Electrochemical deposition of metals and alloys involves the reduction of metal ions
from aqueous, organic, and fused-salt electrolytes. In this book we treat deposition
from aqueous solutions only. The reduction of metal ions Mz(cid:1)in aqueous solution is
represented by
Mz(cid:1) (cid:1)ze→ M (1.1)
solution lattice
This can be accomplished by means of two different processes: (1) an electrodeposi-
tion process in which zelectrons (e) are provided by an external power supply, and
(2) an electroless (autocatalytic) deposition process in which a reducing agent in the
solution is the electron source (no external power supply is involved). These two
processes, electrodeposition and electroless deposition, constitute the electrochemi-
cal deposition. In this book we treat both of these processes. In either case our inter-
est is in a metal electrode in contact with an aqueous ionic solution. Deposition
reaction presented by Eq. (1.1) is a reaction of charged particles at the interface between
a solid metal electrode and a liquid solution. The two types of charged particles, a metal
ion and an electron, can cross the interface.
Four types of fundamental subjects are involved in the process represented by
Eq. (1.1): (1) metal–solution interface as the locus of the deposition process, (2)
kinetics and mechanism of the deposition process, (3) nucleation and growth
processes of the metal lattice (M ), and (4) structure and properties of the
lattice
deposits. The material in this book is arranged according to these four fundamental
issues. We start by considering in the first three chapters the basic components of an
electrochemical cell for deposition. Chapter 2 treats water and ionic solutions;
Chapter 3, metal and metal surfaces; and Chapter 4, the metal–solution interface. In
Chapter 5 we discuss the potential difference across an interface, and in Chapter 6,
Fundamentals of Electrochemical Deposition, Second Edition.
By Milan Paunovic and Mordechay Schlesinger
Copyright © 2006 John Wiley & Sons, Inc.
1
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2 OVERVIEW
the kinetics and mechanisms of electrodeposition. Nucleation and growth of thin
films and formation of the bulk phase are treated in Chapter 7. Electroless deposition
and deposition by displacement are the subject of Chapters 8 and 9, respectively. In
Chapter 10 we discuss the effects of additives in the deposition and nucleation and
growth processes. Simultaneous deposition of two or more metals, alloy deposition,
is discussed in Chapter 11. The manner in which current and metal are distributed on
the substrate is the subject of Chapter 12. Characterization of metal surfaces before
and/or after deposition and during the deposition process is treated in Chapters 13
and 14. Chapter 15 treats modeling of the deposition process. Structure and proper-
ties of deposits are treated in Chapters 16 to 18.
It is seen from the above that the present book contains a number of different types
of material, and it is likely that on first reading, some readers, will want to use some
chapters, whereas others may want to use different ones. For this reason the chapters
and their various sections have been made independent of each other as far as pos-
sible. Certain chapters can be omitted without causing difficulties in reading suc-
ceeding chapters. For example, Chapters 3 (on metals and metal surfaces), 7 (on
nucleation and growth models), 14 (on in situ characterization of deposition
processes), and 15 (mathematical modeling in electrochemistry) can be omitted on
first reading. Thus, the book can be used in a variety of ways to serve the needs of dif-
ferent readers.
1.2. RELATION OF ELECTROCHEMICAL DEPOSITION TO
OTHER SCIENCES
The relation of electrochemical deposition to other sciences may be appreciated by
considering the above-mentioned four types of fundamental problems associated
with Eq. (1.1).
1. The metal–solution interface as the locus of the deposition processes. This
interface has two components: a metal and an aqueous ionic solution. To understand
this interface, it is necessary to have a basic knowledge of the structure and electronic
properties of metals, the molecular structure of water, and the structure and proper-
ties of ionic solutions. The structure and electronic properties of metals are the sub-
ject matter of solid-state physics. The structure and properties of water and ionic
solutions are (mainly) subjects related to chemical physics (and physical chemistry).
Thus, to study and understand the structure of the metal–solution interface, it is nec-
essary to have some knowledge of solid-state physics as well as of chemical physics.
Relevant presentations of these subjects are given in Chapters 2 and 3.
2. Kinetics and mechanism of the deposition process.The rate of the deposition
reactionn[Eq. (1.1)] is defined as the number of moles of Mz(cid:1)depositing per second
and per unit area of the electrode surface:
n(cid:2)k[Mz(cid:1)] (1.2)