Arthur Sherman - Chemical Vapor Deposition for Microelectronics

CHEMICAL VAPOR DEPOSITIONFOR MICROELECTRONICSMATERIALS SCIENCE AND PROCESS TECHNOLOGY SERIESEditorsRointan F. Bunshah, University of California, Los Angeles (MaterialsScience and Technology)Gary E. McGuire, Microelectronics Center of North Carolina (Electronic Materials and Processing)DEPOSITION TECHNOLOGIES FOR FILMS AND COATINGS; Developments and Applications: by Rointan F. Bunshah et alCHEMICAL VAPOR DEPOSITION FOR MICROELECTRONICS; Principles,Technology, and Applications: by Arthur ShermanSEMICONDUCTOR MATERIALS AND PROCESS TECHNOLOGY HANDBOOK; Very Large Scale Integrated Circuits (VLSIC) and Ultra Large ScaleIntegrated Circuits (ULSIC): edited by Gary E.

McGuireSOL-GEL TECHNOLOGY;edited by Lisa C. KleinPrinciples,DevelopmentsandApplications:HYBRID MICROCIRCUIT TECHNOLOGY HANDBOOK; Materials, Processes, Design, Testing and Production: by James J. Licari and Leonard R.EnlowHANDBOOK OF THIN FILM DEPOSITION PROCESSES AND TECHN IOU ES; Principles, Methods, Equipment and Applications: edited byKlaus K. SchuegrafRelated TitlesADHESIVES TECHNOLOGY HANDBOOK: by Arthur H. LandrockHANDBOOK OF THERMOSEl PLASTICS: edited by Sidney H.

GoodmanHANDBOOK OF CONTAMINATION CONTROL IN MICROELECTRONICS;Principles, Applications and Technology: edited by Donald L. TolliverCHEMICAL VAPORDEPOSITIONFOR MICROELECTRONICSPrinciples, Technology, and ApplicationsbyArthur ShermanVarian Research CenterPalo Alto, CaliforniaReprint Edition~NOYES PUBLICATIONSnp -Westwood, New Jersey, U.S.A.Copyright © 1987 by Arthur ShermanNo part of this book may be reproduced in any formwithout permission in writing from the Publisher.Library of Congress Catalog Card Number: 87-11277ISBN: 0-8155-1136-1Printed in the United StatesPublished in the United States of America byNoyes PublicationsFairview Avenue, Westwood, New Jersey 0767510 9Library of Congress Cataloging-in-Publication DataSherman, Arthur.Chemical vapor deposition for microelectronics.Bibliography: p.Includes index.1.

Vapor-plating. 2. Integrated circuits--Designand construction. I. Title.TS695.S54 1987621.381'787-11277ISBN 0-8155-1136-1PrefaceThe objective of the present text on Chemical Vapor Deposition (CVD)is to present a unified picture of an interdiscipl inary field. There are many references that deal in great detail with limited aspects of the subject, but nonethat encompass all elements. For example, early CVD reactors tended to operate at atmospheric pressures, and many researchers studied the fluid dynamicnature of such systems (recirculating flows, buoyancy effects, etc.).

Recently,low pressure systems have become of interest, and by and large, the fluid dynamic character of the reactor flow is not studied in detail. Such an approachis acceptable for initial operation of these systems. However, as demands onthem continue to grow, it becomes necessary to again consider the fluid dynamics. Similarly, many cold-wall as well as hot-wall reactor systems have beenused commercially. Again, as these systems are pushed to their limits, it becomes apparent that there are fundamental differences in their operation.It is doubtful that such differences will be clarified until researchers includefluid dynamics with gas phase kinetics and with surface kinetics in their studies.To summarize, CVD is the study of the flow of reactive gas mixtures withheterogeneous surface reactions.

Because of the inordinate complexity of theproblem, most studies of the subject have been empirical. It is the author'shope that the present text will encourage more studies of CVD phenomenafrom first principles.In the first chapter, we consider the fundamental nature of the thermallyinduced CVD. Initially, we consider the behavior of CVD reactions under theassumption of chemical equilibrium. Much useful information can be derivedby this technique, especially for very complex chemical systems where severaldifferent solid phases can be deposited. In order to extend our understandingof CVD, it is necessary to consider reacting gas flows where the rates of chemical reactions are finite. Therefore, the next subject considered is the modelingof CVD flows, including chemical kinetics.

Depending on processing conditions, the film being deposited may be amorphous, polycrystalline, or epitaxial,vviPrefaceso the morphology of deposited films is discussed briefly. Finally, the thermalCVD reactor configurations that have been typically used in research and development are reviewed.In addition to thermally-created CVD films, much work has been doneusing glow discharges to modify the deposition. Therefore, Chapter 2 reviewsthe fundamentals of plasma-enhanced CVD (PECVD). Initially, the basic character of a plasma is covered.

Then we discuss the influence of the reactor configuration on the plasma behavior and PECVD deposition. The two majorPECVD reactor systems are reviewed, and then several new concepts are considered.The next three chapters review the deposition of thermally-induced dielectric films (Chapter 3) and metallic conducting films (Chapter 4), as wellas plasma-enhanced films of either type (Chapter 5). The many chemical systems employed to create these films are considered, and the nature of theresulting films is presented.

Films studied are silicon dioxide, silicon nitride,polysilicon, epitaxial silicon, the refractory metal silicides, tungsten and aluminum.Chapter 6 is devoted to typical commercially-available CVD reactor systems, including cold-wall and hot-wall systems. Several new commercial reactors are also reviewed.Finally, Chapter 7 covers methods commonly used for film evaluation.The first portion covers techniques for assessing the physical nature of thefilms produced, while the latter portion reviews methods of chemical analysisof thin films.The author wishes to express his gratitude to Varian Associates for providing the necessary facil ities for the preparation of the manuscript, and toMrs. Nancy Anderson for her patient and careful typing of the text.

Finally,I must thank Drs. G.J. Reynolds, C.B. Cooper III, J.A. Fair and S.B. Felch fortheir assistance in reviewing the manuscript.Palo Alto, CaliforniaJuly, 1987Arthur ShermanNOTICETo the best of the Publisher's knowledge theinformation contained in this publication isaccurate; however, the Publisher assumes noliability for errors or any consequences arising from the use of the information contained herein. Final determination of thesuitability of any information, procedure,or product for use contemplated by anyuser, and the manner of that use, is the soleresponsibility of the user.The book is intended for information only.The reader is warned that caution mustalways be exercised when dealing withhazardous materials, and expert adviceshould be obtained at all times when implementation is being considered.viiiContents1.

FUNDAMENTALS OF THERMAL CVD1.1 Introduction1.2 Chemical Equilibrium1.2.1 Law of Mass Action1.2.2 Reactions with Multiple Species1.2.3 Minimization of Gibbs Free Energy1.3 Modeling of Flow and Chemical Kinetics1.3.1 Diffusion vs. Surface Controlled Deposition1.3.2 Effects of Gas Phase Kinetics1.4 Film Morphology1.5 Laboratory Thermal CVD Reactors1.5.1 Cold Wall Systems-Single Wafer1.5.1.1 Tube Reactor, Parallel Flow1.5.1.2 Tube Reactor, Normal Flow1.5.1.3 Heating Systems1.5.2 Cold Wall Systems-Multiple Wafers1.5.2.1 Tube Reactor1.5.2.2 Bell Jar Reactor, Barrel Susceptor1.5.2.3 Bell Jar Reactor, Barrel Susceptor, Radial Flow1.5.2.4 Pancake Reactor1.5.3 Cold Wall Systems-Continuous Belt1.5.4 Hot Wall SystemsReferences113371013141728313131323333343435363637382.

FUNDAMENTALS OF PLASMA-ASSISTED CVD2.1 Introduction2.2 Plasmas2.2.1 Elevated Electron Temperatures in Plasmas2.2.2 Characteristic Parameters in Plasmasix4040414143xContents2.2.3 Electron Cyclotron Resonance in Plasmas2.3 Reactor Influence on Plasma Behavior2.3.1 DC/AC Glow Discharges2.3.2 AC Discharges with Unequal Area Electrodes2.3.3 Frequency Effects on RF Plasma Reactor Behavior2.3.4 Influence of Applied Magnetic Fields on RF PlasmaReactors2.4 Plasma-Enhanced CVD (PECVD) Reactors2.4.1 Cold-Wall, Parallel-Plate PECVD Reactors2.4.2 Hot-Wall, Parallel-Plate PECVD Reactors2.5 Novel Plasma-Enhanced CVD Reactors2.5.1 Electron Cyclotron Resonance (ECR) CVD Reactor2.5.2 Parallel Electrode, Hot-Wall PECVD Reactor2.5.3 Ionic Systems ConceptReferences46484850535456575960606364643.

THERMAL CVD of Dielectrics and Semiconductors3.1 Introduction3.2 Silicon Dioxide3.2.1 Atmospheric Pressure3.2.2 Low-Pressure3.2.3 Reflow Phenomena3.2.4 Tetraethylorthosilicate (TEOS) Source3.2.5 Diacetoxyditertiarybutoxysilane (DADBS) Source3.3 Silicon Nitride3.4 Polysilicon3.4.1 Deposition Behavior.3.4.2 Electrical Resistivity of Doped Films3.5 Epitaxial Silicon3.5.1 The CVD Process for Epi Silicon3.5.2 Surface Effects3.5.3 Defects .