VLSI electronics microstructure science

212 Pages·1990·21.491 MB·English

by  Anant G Sabnis

VLSI Electronics
Microstructure Science
A Treatise Edited by
Norman G. Einspruch
College of Engineering
University of Miami
Coral Gables, Florida
VLSI Electronics
Microstructure Science
Volume 22
VLSI Reliability
Anant G. Sabnis
AT&T Bell Laboratories
Allentown, Pennsylvania
AKT
Published by arrangement ACADEMIC PRESS, INC.
with AT&T Harcourt Brace Jovanovich, Publishers
San Diego New York Boston
London Sydney Tokyo Toronto
This book is printed on acid-free paper. @
Copyright © 1990 by Bell Telephone Laboratories, Incorporated.
Ail Rights Reserved.
No part of this publication may be reproduced or transmitted in any form or
by any means, electronic or mechanical, including photocopy, recording, or
any information storage and retrieval system, without permission in writing
from the publisher.
Academic Press, Inc.
San Diego, California 92101
United Kingdom Edition published by
Academic Press Limited
24-28 Oval Road, London NWl 7DX
Library of Congress Cataloging-in-Publication Data
Sabnis, Anant G.
VLSI reliability / by Anant G. Sabnis.
p. cm. ~ (VLSI electronics ; v. 22)
Includes bibliographical references.
ISBN 0-12-234122-8 (alk. paper)
1. Integrated circuits-Very large scale integration-Reliability.
I. Title. II. Series.
TK7874.V56 vol. 22
621.39'5 s-dc20
[621.39'5] 89-17892
CIP
Printed in the United States of America
90 91 92 93 9 8 7 6 5 4 3 2 1
This book is dedicated to
Animesh, Nilaya, Jyoti, and to many
fond memories of my parents.
Foreword
Integrated circuits have become crucial to the safety, welfare, and en­
joyment of life in modern civilization. We have become dependent on
these devices for transportation, communications, business, and leisure.
In the past, the consequence of failure was usually inconvenience and
some expense. Now, failure of ICs in many applications can have dire and
even fatal results. Thus, it is imperative that the producer of these devices
understands what can cause them to fail so that weak ICs are not shipped
to the customer. If you make integrated circuits or manufacture systems
which use them, poor reliability can jeopardize your customer, your com­
pany, and maybe your own future.
By and large, the reliability of modern integrated circuits is very good
indeed. Typically, less than one percent fail in ten years of service. But
this can lead to a false sense of security since failure rates can be much
higher if appropriate precautions are not observed. As this book empha­
sizes, device failure can be caused by a wide variety of mechanisms,
ranging from electrical overstress to nuclear radiation. In-depth under­
standing of all IC failure mechanisms discussed herein requires the disci­
plines of electrical, mechanical, and metallurgical engineering, chemistry,
and solid state physics. However, Dr. Sabnis avoids much of the gibber­
ish and presents pertinent information in a clear and lucid style. Few of
these failure mechanisms are new; most have been observed in various
forms throughout the history of semiconductors. However, they continue
to reappear in each new generation of devices, often in subtle and insidi­
ous ways.
As devices become more complex and geometries more dense, more
care must be taken to avoid reliability problems. This means that the
designers and process specialists must be aware of potential failure mech­
anisms, how to detect them, and how to avoid them. As evidenced by the
extensive literature, this is neither simple nor easy. A comprehensive
xii Foreword
treatment would occupy many volumes. However, this book is an excel­
lent place to start. Dr. Sabnis has provided a broad overview of the major
failure mechanisms afflicting modern semiconductor devices, and he has
compiled a carefully selected list of references for each subject. He has
also summarized many of the methods developed over time to evaluate
the reliability of these devices. I strongly recommend this book to all
those—both neophytes and experts—involved in the design, fabrication,
and application of integrated circuits.
Carl W. Green
Head, IC Test Technology
AT&T Bell Laboratories
Preface
VLSI Reliability covers a broad spectrum of reliability issues. The
reader is presented with major topics in IC reliability—from basic con­
cepts to packaging issues. Also included in this book are chapters on
failure analysis techniques, radiation effects, and reliability assurance and
qualification. Each topic has been discussed in detail, and an extensive
list of references is provided at the end of each chapter. This book is
written for the benefit of both experts and beginners in the field of IC
reliability. It also has great potential to serve as a textbook for undergrad­
uate and graduate students.
Quite a few books have appeared in the literature on the subject of IC
reliability, but they typically emphasize theoretical aspects. However, to
be successful in IC business, managers and engineers require insights into
the practical aspects of VLSI reliability. This book is intended to serve
that puφose.
I am indebted to Messrs. G. T. Cheney, G. L. Mowery, J. T. Nelson,
and P. T. Panousis for providing the necessary resources and encourage­
ment to write this book. I am grateful to Messrs. C. W. Green, Y. Na-
kada, J. T. Nelson, and S. K. Tewksbury for reading the manuscript and
providing many valuable suggestions and comments that helped improve
the quality of this book. Many sincere thanks to Ms. Natalie Kaminski,
Ms. Nancy Co vis, and their co-workers for flawless typing of the manu­
script. I also thank Ms. Judy BuUard and her co-workers for providing the
artwork, and Mr. A. J. Masessa and Mr. J. M. Szabo, Jr. for their help in
taking SEM pictures.
This book would not have been possible without the help and under­
standing of my wife, Jyoti, and our children, Animesh and Nilaya. They
were not only patient during the preparation of the manuscript but also
helped to edit it.
XIII
Chapter 1
Introduction
Since the discovery of the point-contact transistor by Bell Laboratories
some 40 years ago, myriads of semiconductor integrated circuits (ICs) and
electronic equipment have evolved worldwide. No other single invention
has had such a phenomenal impact on the lifestyle and culture of human­
kind in such a short period of time. People in all walks of life in this
electronics generation are becoming increasingly dependent on semicon­
ductor products for communication, data transmission, transportation,
banking, and many other daily activities that are important for their liveli­
hoods. Furthermore, the ceaseless upheaval of the electronics revolution
has injected a new definition of the military might of a nation that is
measured in terms of its abiUty to attack or defend from space with
sophisticated electronic remote controls. Simply stated, the reliability of
these advanced electronic ICs and the systems that use them is not merely
a matter of survival for the electronic industry in the face of fierce interna­
tional competition but may be a matter of life and death for the human
race.
The electronics industry, from its humble beginning of manufacturing
discrete transistors in the late 1940s and early 1950s, has evolved into the
largest manufacturing segment of U.S. business.* Beginning with the his­
torical breakthrough invention of the first IC by Jack Kilby^ in 1958 came
the first commercial monolithic IC in 1961, the metal oxide semiconductor
(MOS) IC in 1962, and the CMOS IC in 1963. The path of continued
advancement of ICs is marked by distinct periods of small-scale integra­
tion (SSI), medium-scale integration (MSI), large-scale integration (LSI),
and the present, very large-scale integration (VLSI) leading to the future
ultra-large scale integration (ULSI).
1
2 1. introduction
Designers of ICs are being challenged to satisfy demands for high
switching speeds, reduced power consumption, and increased packing
density while meeting high reliability objectives. In response, silicon ICs
designed with sophisticated Computer Aided Design (CAD) tools and
fabricated with state-of-the-art VLSI technology are being demonstrated
to meet the challenges. An excellent example is the IC that facilitates
transmission and reception of speech, data, and video information at
speeds beyond 420 MHz at room temperature over a single fiber.An­
other example is the recent 64K CMOS SRAM (complementary MOS
static random-access memory) with access times of 3-5 ns at liquid nitro­
gen temperature and below 10 ns at room temperature.^ As the perfor­
mance of ICs is being pushed to the Hmits of mature technologies by
incoφorating novel design concepts,^ the conventional hard-wired elec­
trical testers supplying digital data up to 200 MHz with timing accuracies
of about ±250 ps and resolutions to about 20 ps are rapidly becoming
outdated. The challenges in testing the modern VLSI circuits are bringing
forward new measurement concepts that employ a phenomenon of nonin­
vasive light beam interacting with an electric field with reduced pin load­
ing (<1 pF) effects.^
The ability to test the VLSI circuits is crucial in assuring their reUabil-
ity. The test methods and systems intended for discovering weaknesses
must not themselves become the reliability hazards.^ While employing
beams of electrons and photons to measure VLSI circuit performance,
the designer must consider their interaction with materials and the reli­
ability consequences. Most of the IC failure mechanisms known today
were first discovered in the ICs and were later studied in discrete devices
to enhance the understanding needed to prevent or eliminate them. Many
of the same mechanisms discovered during the discrete and SSI days still
exist in today's VLSI age. With every next generation of device scaling,
the sensitivity of ICs to the known mechanisms has increased severalfold.
For example, the hot carriers existed in MSI, but their damaging magni­
tudes were revealed in LSI, and the effects continue to threaten the VLSI
and ULSI developments. There is an endless need to develop finer under­
standing of reliability issues as we continue to stay on a course of reaching
new heights in technological excellence.
This book is written in an attempt to compile the past and recent infor­
mation of reliability issues applicable to the present VLSI circuits. For
any reliability engineer, mastering an art of analyzing a mass of reliability
data by statistical methods is necessary but not sufficient. That art must
be complemented by a great deal of understanding of the various mecha­
nisms that cause those failures so that a proper sense can be put into the
data analysis and a meaningful feedback can be provided to circuit and
1. Introduction 3
system designers and processing engineers. Although no one person can
master all aspects of reliability, with the growing complexity of the VLSI,
it is essential for a statistician to grasp the extent of the influence of
physics and chemistry of the mechanisms on the mathematical estima­
tions of reliability measures. By the same token, the students of mecha­
nisms must appreciate the limits of statistical methods that put a practical
sense into the observed variabilities of reliability information. With this in
view, this book is organized to cover a wide spectrum of the VLSI reli­
ability discipline.
The focus of this book is specifically on VLSI reliability. The ICs are
basic components of many electronic instruments and systems. The sys­
tems are designed to meet well-defined reliability objectives. To meet
those objectives, system level reUability models are developed and, on
the basis of the models, the reliability objectives are apportioned to the
subsystems and individual components. When, in a multicomponent sys­
tem, failures occur statistically independent of each other, the system is
modeled as a series system in a reliability sense. The series model implies
that the failure of any one component can lead to system malfunction. A
series model illustrated in Fig. 1.1 indicates division of components in two
categories: the critical and noncritical components. Typically, the critical
components contribute to the early failures. The ICs fall into this cate­
gory. The noncritical components are those that, by experience, are
known to contribute very little to system failures, for example, resistors
and capacitors. In such systems, if one component fails, the whole system
becomes inoperable. In the systems that have to continue working despite
failure of individual components, failure rates must be reduced by design­
ing in redundancy for the critical parts. Such systems are described by
parallel or redundant models illustrated in Fig. 1.2. Each box may be a
discrete component or a subassembly. In any case, the reliability objec­
tives of ICs are dictated by the system designers on the basis of the model
used for apportioning the reliabiUty. In general, the systems contain com­
plex combinations of series and parallel models.
The subject of VLSI reliability is science, art, and technology combined
in one discipline. The main function of this discipline is to develop models
CRITICAL NONCRITICAL
COMPONENTS COMPONENTS
— 2 —T] [ñ^2J—[n^]— η
Fig. 1.1. A system-level series model for component reliability; components are divided
into critical and noncritical categories.