Table Of ContentCONTRIBUTORS
B. R. Apple ton J. M. Poate
Pietro Baeri Emanuele Rimini
J. C. Bean T. W. Sigmon
Salvatore Ugo Campisano Frans Spaepen
A. G. Cullis David Turnbull
Gaetano Foti Martin F. von Allmen
J. F. Gibbons C. W. White
C. Hill J. S. Williams
S. S. Lau S. R. Wilson
James W. Mayer D. M. Zehner
Laser Annealing
of Semiconductors
Edited by
J. M. POATE
Bell Laboratories
Murray Hill, New Jersey
JAMES W. MAYER
Department of Materials Science
Cornell University
Ithaca, New York
1982
ACADEMIC PRESS
A Subsidiary of Harcourt Brace Jovanovich, Publishers
New York London
Paris San Diego San Francisco Sao Paulo Sydney Tokyo Toronto
COPYRIGHT © 1982, BY ACADEMIC PRESS, INC.
ALL 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.
Ill Fifth Avenue, New York, New York 10003
United Kingdom Edition published by
ACADEMIC PRESS, INC. (LONDON) LTD.
24/28 Oval Road, London NW1 7DX
Library of Congress Cataloging in Publication Data
Main entry under title:
Laser annealing of semiconductors,
Includes bibliographical references and index.
1. Semiconductor industry—Laser use in—Congresses.
2. Semiconductors. I. Poate, J. M. II. Mayer, James W.,
Date
TA1673.L34 1982 621.3815'2 82-8816
ISBN 0-12-558820-8 AACR2
PRINTED IN THE UNITED STATES OF AMERICA
82 83 84 85 9 8 7 6 5 4 3 2 1
List of Contributors
Numbers in parentheses indicate the pages on which the authors' contributions begin.
B. R. Appleton (111), Solid State Division, Oak Ridge National Labora-
tory, Oak Ridge, Tennessee 37830
Pietro Baeri (75), Istituto di Struttura della Materia, Universita di Cata-
nia, 95129 Catania, Italy
J. C. Bean (247), Bell Laboratories, Murray Hill, New Jersey 07974
Salvatore Ugo Campisano (75), Istituto di Struttura della Materia, Uni-
versita di Catania, 95129 Catania, Italy
A. G. Cullis (147), Royal Signals and Radar Establishment, Malvern,
Worcestershire WR14 3PS, England
Gaetano Foti (203), Istituto di Struttura della Materia, Universita di Cata-
nia, 95129 Catania, Italy
J. F. Gibbons (325), Stanford Electronics Laboratories, Stanford Univer-
sity, Stanford, California 94305
C. Hill (479), Plessey Research (Caswell) Limited, Allen Clark Research
Centre, Caswell, Towcester, Northamptonshire NN12 8EQ, England
S.S. Lau (439), Department of Electrical Engineering and Computer
Sciences, University of California, San Diego, La Jolla, California
92093
James W. Mayer (1), Department of Materials Science, Cornell Univer-
sity, Ithaca, New York 14853
J. M. Poate (1, 247), Bell Laboratories, Murray Hill, New Jersey 07974
Emanuele Rimini (203), Istituto di Struttura della Materia, Universita di
Catania, 95129 Catania, Italy
ix
X LIST OF CONTRIBUTORS
T. W. Sigmon (325), Stanford Electronics Laboratories, Stanford Univer-
sity, Stanford, California 94305
Frans Spaepen (15), Division of Applied Sciences, Harvard University,
Cambridge, Massachusetts 02138
David Turnbull (15), Divisison of Applied Sciences, Harvard University,
Cambridge, Massachusetts 02138
Martin F. von Allmen (43, 439), Institute of Applied Physics, University of
Bern, CH-3012 Bern, Switzerland
C. W. White (111, 281), Solid State Division, Oak Ridge National Labora-
tory, Oak Ridge, Tennessee 37830
J. S. Williams (383), Department of Communication and Electronic Engi-
neering, Royal Melbourne Institute of Technology, Melbourne, Vic-
toria 3000, Australia
S. R. Wilson (111), Semiconductor Group, Motorola, Inc., Phoenix, Ar-
izona 85008
D. M. Zehner (281), Solid State Division, Oak Ridge National Labora-
tory, Oak Ridge, Tennessee 37830
Preface
In the past five years there has been a remarkable display of interest in
the laser annealing of semiconductors. Interest in this field developed in
the period 1977-1978 with workshops in Albany, New York, and in Cata-
nia, Italy, followed by symposia at the Materials Research Society meet-
ings in Boston from 1978 to 1981. By July 1981 there were over 800 publica-
tions in this field. The contributors to this volume have been involved in
the field since its emergence in 1977.
The subject deals with the materials science of surfaces that have been
subjected to ultrafast heating by intense laser or electron beams. The time
scale is such that layers can melt and recrystallize in a few hundred nano-
seconds. This rapid resolidification of semiconductors has led us into
novel regimes of phase formation and has served as a means of removing
implantation damage. It was this latter aspect that stimulated the field.
We believe that the phenomena of not only the energy deposition and
heat flow but also of the basic crystal growth processes are sufficiently
well understood to warrant this volume. The chapters follow a logical
sequence from basic concepts to device structures.
We should like to thank our fellow contributors for their efforts. They
revised their chapters as necessary to fit within a common framework. We
especially acknowledge our friends in Catania for their efforts.
Dawn and Betty, as always, gave us unflagging support.
LASER ANNEALING OF SEMICONDUCTORS
Chapter Ί
Introduction
J. M. POATE
Bell Laboratories
Murray Hill, New Jersey
and
JAMES W. MAYER
Department of Materials Science
Cornell University
Ithaca, New York
I. Directed Energy Processing of Semiconductors 1
II. Energy Deposition and Heat Flow 4
III. Interfaces and Surfaces 7
IV. Epitaxy and Alloying 12
V. Surface Crystallization and Alloying—Perspectives 13
List of Symbols 14
I. Directed Energy Processing of Semiconductors
A new field of materials science—directed energy processing—has
emerged in the past five years for the processing and modification of the
surface layers of semiconductors. Directed energy sources such as lasers
or electron beams are used to heat the surface. The unique temporal and
spatial control exercised over the heat flow by these beams allows forma-
tion of quite novel structures and alloys. For example, surface layers can
be melted and solidified in exceedingly short times to produce metastable
alloys. The dimensions of the layers that can be modified by the incident
beams are just those required by Si integrated circuit technology.
/
Copyright © 1982 by Academic Press, Inc.
All rights of reproduction in any form reserved.
ISBN 0-12-558820-8
2 J. M. POATE AND JAMES W. MAYER
The materials and dimensions of the Si technology are beautifully illus-
trated in the transmission electron microscopy photograph in Fig. 1,
which is a cross section through an actual insulated-gate field-effect trans-
istor (IGFET) test structure. The source-drain regions were fabricated by
As implantation followed by an annealing treatment in 0 at 900°C for 35
2
min. The resulting n + junction depth (a in Fig. 1) is 1000 Ä, with the same
Fig. 1. Transmission electron microscopy photograph of a vertical section through an
IGFET structure at the edge of a gate. The parameters a and c, respectively, are the
implanted junction depths and lateral penetration of the implanted junction following the
anneal. [From T. T. Sheng and R. B. Marcus, J. Electrochem. Soc. 881, 128 (1981).]
3
1. INTRODUCTION
lateral spread (c in Fig. 1) under the gate as measured from the position of
the original implantation. The gate contact is 3500 Ä of polycrystalline Si
on a 250-Ä Si0 gate oxide. The thicknesses of the active regions are
2
LASER-
RECRYSTALLIZEDSi
SOURCE CONTACT
GATE
CONTACT
*♦ QATI WIDTH 30jim
Fig. 2. (a) Cross section of an «-MOSFET test structure fabricated on laser-recrys-
tallized poly-Si, 0.5 μπι thick, on amorphous Si0. (b) Optical micrograph of the test struc-
2
ture showing the drain and source contacts for three gate lengths of 3, 6, and 30 μπι.
(From G. K. Celler, Bell Laboratories.)
4 J. M. POATE AND JAMES W. MAYER
confined to the outer micrometer of the Si structures—a distance compat-
ible with directed energy processing.
The first demonstrations of the utility of directed energy processing
came from the annealing of implantation damage using lasers. Thus the
term "laser annealing" was coined. It is something of a misnomer, as
most of the annealing mechanisms are in fact due to liquid or solid phase
recrystallization. The field has progressed far beyond the annealing of
implantation damage, as demonstrated in Fig. 2. It is possible to recrystal-
lize amorphous or polycrystalline Si on amorphous substrates by laterally
sweeping a Si melt puddle with a moving laser or particle beam. Very
large grains or even single-crystal Si can be produced by this technique,
which may lead to a new generation of devices. Figure 2a shows a
schematic cross section of an A-channel metal-oxide-semiconductor
field-effect transistor (MOSFET) fabricated in a 0.5-^m-thick film of Si.
The Si layer was deposited in the form of small-grain (0.1 μΐη) polycrystal-
line Si on 1 μ,πι of amorphous Si0 which had been thermally grown on a
2
Si wafer. The Si layer was then heated by a scanning continuous-wave
(cw) Ar+ laser and recrystallized into grains with average lateral dimen-
sions of 5 /im. The actual test devices have gate oxides of 270-Ä thickness
with channel lengths from 100 to 0.3 μπ\ and channel widths from 120 to 20
jLtm. An optical micrograph (Fig. 2b) shows a test structure with different
channel lengths of 3, 6, and 30 /xm and constant channel widths. The
electron surface mobilities are found to increase with decreasing channel
length and approach that of devices in single-crystal Si. The success of
these devices results from the ability to produce very large grain Si layers
on an amorphous, insulating substrate. They could not be fabricated with-
out the laser recrystallization techniques.
There is little doubt that the rapid expansion of this field is due to the
driving force of the semiconductor industry. New processing techniques
are needed to produce structures on the submicrometer scale. Much of
the research interest, however, centers around the fact that the directed
energy techniques allow the exploration of new realms of materials sci-
ence. Spaepen and Turnbull in Chapter 2 present the concepts of solidifi-
cation and crystallization pertinent to the present subject.
II. Energy Deposition and Heat Flow
The facility of rapidly heating and cooling surface layers without heat-
ing the bulk depends on the pulse duration time r and the coupling depths
of the heat source. These parameters for both laser and electron-beam
