- Email: [email protected]
Metallurgy of semiconductors
558
BOOK
in the planning and editing bears full fruit. The question may be asked: who will find this Dictionary most useful? Probably not students, because the level is too high (incidentally, more references should have been given, particularly in the case of advanced topics, to elementary introductions to the subject). Teachers will certainly want to consult it, for instance to see what line of approach is followed by a specialist on a given problem, or to get information quickly in a concise way. But the main user is likely to be the narrow specialist, who wants to be reminded, again consuming as little time as possible, of what he studied a long time ago, or to find a quick explanation of concepts and terms he has found in the literature. For him it will be essential that the supplementary volumes should be completely up-to-date and that they should really include all terms, particularly those used by theorists, and names for special devices (of which there is a new crop in practically every issue of Solid-State Electronics!). In fact there is evidence that this is the kind of public at which the Editors have principally aimed. When issuing the supplementary volumes having the same users in view, they will probably find that the size they anticipate for these supplements (as indicated by their price) is insufficient, at least for the first few years, if the above requisites are to be met. Examples of terms now widely used and missing from the Dictionary, just quoting at random, are “Magnetoabsorption”, “Wannier functions”, “Propagator” and, as was inevitable, many solid-state devices. The general lay-out of the Dictionary was described in the review of the first volume and the comments then made still stand. Now that the work is finished, one may add that the Dictionary itself consists of seven volumes, page size 25 x 19 cm, with 5941 pp. in all. The 8th Volume (495 pp.) is the Index, and the 9th will be the Glossary. The price works out at about 3$d (4 cents) per page, which is on the high side. A few words on the Index may be appropriate, since it will be consulted again and again when one fails to find a particular entry immediately in the Dictionary. The Index is meant to give all reasonable variations of the terms listed in the Dictionary, as well as showing where many thousands of topics are dealt with that do not form the subject of separate articles, e.g. “Antisymmetry”, “Band
REVIEWS
Spectra”, “Band Theory”. In this respect one has the impression that it does not go far enough and it will be desirable to go through all the entries again and publish a new much enlarged edition in the future: after all, a work of this kind almost stands or falls on the ease with which it provides Referring to the above examples, information. according to the Index the concept of antisymmetry is dealt with only in the short elementary entry on the exclusion principle. It seems very probable that something more fundamental is said elsewhere. Again, while several entries are referred to under “Band theory of solids”, the most extensive (Bloch theory) is not given. r\Tophysics library can afford to be without this work. Everybody I know who has made a habit of consulting it agrees that its usefulness grows with prolonged acquaintance, and that just perusing it in a so-called idle moment can be most rewarding. Every time one finds some really outstanding contributions, models of how to convey the maximum amount of information clearly, concisely and as simply as possible. Bedford College University of London
I,. PINCIIERLE
Yr:. M. SHASHKOV(Author&d Translation from the Russian by J. E. S. BRADLEY):Metallurgy of Semiconductors. Consultants Bureau Enterprises, New York, 1960. pp. 173 $9.50. THE metallurgy of semiconductors is a subject with a short tradition. It began in 1948 with the announcement of the germanium transistor, which required the preparation of this elemental semiconductor in single crystal form with a high degree of chemical purity and structural perfection heretofore foreign to metallurgists and chemists. Today, 15 years later, this subject has broadened considerably, and is a well-defined and important branch of the rapidly growing tree of materials science. In the 173 pages of this book with its 293 references covering the period through 1957, the author attempts to survey semiconductor metallurgy by providing a compendium of metallurgical and chemical techniques applicable solely to germanium and silicon technology. The subject matter is arranged in such a manner as to take the reader essentially through a materials obstacle course in
BOOK
REVIEWS
the preparation of germanium and silicon specifically for use in transistor-like devices. This includes purification, crystal growth, techniques for outlining dislocations, incorporation of desired impurities and their diffusion and distribution coefficients, heat treatment effects, and the formation of p-n junctions. This plan is essentially a good one, but the somewhat obsolete nature of the material and the often superficial and restrictive treatment of subject matter leaves much to be desired. In reading this book, there is a constant urge to refer to the literature for significant, explanatory details. Even this is made difficult since the references, though extensive, appear not in the text but in a summary form at the beginning of each section. Hence, locating a specific contribution by a referenced author is not easy. In addition, the absence of an index in such a reference book is inexcusable. The book has 9 Chapters with 65 Figures and 16 Tables, In Chap. I, the reader is introduced to those physical, electrical and optical properties of germanium and silicon which are important to materials evaluation and to device technology. This is as it should be, but unfortunately the author does not treat this important introductory material in a satisfactory manner. First, there are no schematic diagrams illustrating phenomenologically such important concepts as electron and hole formation, injection of carriers, carrier mobility and recombination processes. Such visual aids would be most helpful to the student and beginner in this field of metallurgy. Second, the description of minority carrier lifetime is inaccurate, as are some of the density constants. These could be errors of translation which, nevertheless, are inexcusable. Finally, the optical properties are not presented in sufficient detail, being accorded only one half-page. In logical sequence Chaps. II and III discuss chemical and metallurgical methods of purifying germanium and silicon for device applications. All of the important chemical approaches are treated, and conveniently outlined by the use of flow charts. However, the text is somewhat obtuse, many statements conveying little information. It is also unfortunate that much of the data is out of date, e.g. silicon chloride reduction with hydrogen is now the standard commercial process for preparing pure silicon in this country, and not the
559
reduction of silicon tetrachloride with zinc. Also disconcerting are several errors and omissions in the referencing of chemical techniques, which again may be due in part to translation. For example, “Beketov’s process” is mentioned on several occasions, and it appears that Beketov is indeed F. M. Becket who described the zinc reduction of Sic14 in U.S. Patent 1,386,227. One also expects to find Van Arkel cited for his pioneering work in this same area, but no reference to him is found in the bibliography. Finally, the Siemens process is nowhere mentioned in connection with the author’s description of the trichlorosilane process for preparing the highest purity silicon. These errors make one cautious to accept other information with which the reader is less familiar. The metallurgical methods (Chap. III) are concerned with techniques of purification after chemical reduction. These are adequately covered by the author. They include the principles of zone refining, controlled recrystallisation by both Bridgman and Czochralski techniques, the theory of impurity distributions in solid, liquid and vapor systems, and a description of the apparatus used in these various purification techniques. In some cases the treatment is highly mathematical, and does not provide a real insight into the phenomenological processes involved. Chapter VI deals with growth of single crystals and structural defects resulting from such growth. The commonly used growth techniques, horizontal zone, Czochralski (vertical) and floating zone are presented in some detail along with the effects of such parameters as temperature gradient, growth velocity and crystal size. However, inadequate treatment is given to solution and vaporphase growth. The discussion of defects, such as twinning and dislocations, leaves much to be desired especially as regards their origin during growth, the control of their density and distribution, and their influence on properties important to both transport behavior and device fabrication. In addition, the micrographs portraying these defects are poor; and where data are presented, they are not in a definitive form. In fact, some of it is questionable. For example, it is emphasised that slip or shear is not observed on indenting germanium at temperatures up to 900°C; and indeed, there is published evidence to the contrary.
560
BOOK
REVIEWS
The effects of heat treatment on the electrical behavior of Ge and Si crystals are touched upon briefly in Chap. V, while Chaps. VI and VII are concerned with diffusion and the incorporation of impurities to produce crystals with desired electrical characteristics. Diffusion coefficients of the impurities commonly used to create electrical p-n junctions in Ge and Si are given, and methods are outlined for doping crystals both from the melt and the vapor, particularly to produce large ingots of uniform carrier concentration. So far as they go, these 3 Chapters do a fairly adequate job with the help of references which are extensive. However, it is unfortunate that the material presented is aimed too much at device applications. This tends to make the treatment too restrictive in scope as evidenced, for example, by the absence of data and discussion on solid solubility of impurities in Chaps. VI and VII. It is interesting where the two books cover the same material, HANNAY’S Semiconductors published in 1959 is both more up-to-date and technically more incisive than this book published a year later. Chapter VIII is concerned almost exclusively with techniques of creating electrical p-n junctions and regions of graded conductivity for transistorlike devices. These techniques include selective impurity additions during growth, changes in impurity distribution coefficients with growth rates, gradient melting and traveling zone involving alloying, and solid-state diffusion of impurities with different diffusion coefficients. Hence, in this Chapter, junction techniques are described which make use of principles established in earlier Chapters of the book. The same can be said of the final Chapter, which deals with etching procedures used to outline dislocations and electrical structures in devices. In summary, this work does not do justice to the broad and important science of the metallurgy of semiconductors. The book is restrictive in its scope and, as such, might more properly have been titled Metallurgy of Germanium and Silicon for Transistor Applications. But even here, the author seems to be more interested in producing a balanced history of the subject than a definitive account. Hence, it is not of general use as a text book for the student who wishes to understand the elementary aspects of a particular topic without the tedium of extensive referencing. The concept of
the book is a good one, and I only wish it had been better executed. Its chief value lies in the logical way the topics are presented. RCA Laboratories Princeton, N. J.
F. D. Rosa
J. KIIAMBATA: Introduction to Integrated Semiconductor Circuits. John Wiley, New York, 1963. pp. 219 + 8 bibliography + 5 index. $7.50.
ADI
THIS book is intended,
in the author’s own words, “to serve as an introductory guide for technical and management people in the electronics industry who are on the threshold of becoming involved in the new and fascinating field of Integrated Circuits”. Concentrating as it does on the semiconductor type of integrated circuit, only cursory attention is given the discrete component approach to microelectronics, and also relatively little attention is given to film approaches. The book is on a highly descriptive level, and appears to be written by an author highly oriented to the applications and with little or no direct experience in semiconductor integrated circuits himself. While he has learned a great deal about such circuits, the treatments do show a vagueness in certain matters which arise apparently from this lack of direct experience. On the other hand there are few if any major errors in technical matters, and the work appears to have been carefully written and edited. The work thankfully omits much of the generalized philosophy of microelectronics about which too much has already been written and said, and after an introductory section goes directly into the techniques and process of semiconductor circuits, based upon the planar technique. The treatment, while general, is adequate for the introductory purposes mentioned above, and also serves as an adequate reference for many details of the fabrication processes. The book cannot be recommended as an adequate technical survey for specialists, however, nor does the author really make any such claim. The “third section contains the meat of the book”, again to use the author’s own words, and in this section he also displays the areas of his
BOOK
in the planning and editing bears full fruit. The question may be asked: who will find this Dictionary most useful? Probably not students, because the level is too high (incidentally, more references should have been given, particularly in the case of advanced topics, to elementary introductions to the subject). Teachers will certainly want to consult it, for instance to see what line of approach is followed by a specialist on a given problem, or to get information quickly in a concise way. But the main user is likely to be the narrow specialist, who wants to be reminded, again consuming as little time as possible, of what he studied a long time ago, or to find a quick explanation of concepts and terms he has found in the literature. For him it will be essential that the supplementary volumes should be completely up-to-date and that they should really include all terms, particularly those used by theorists, and names for special devices (of which there is a new crop in practically every issue of Solid-State Electronics!). In fact there is evidence that this is the kind of public at which the Editors have principally aimed. When issuing the supplementary volumes having the same users in view, they will probably find that the size they anticipate for these supplements (as indicated by their price) is insufficient, at least for the first few years, if the above requisites are to be met. Examples of terms now widely used and missing from the Dictionary, just quoting at random, are “Magnetoabsorption”, “Wannier functions”, “Propagator” and, as was inevitable, many solid-state devices. The general lay-out of the Dictionary was described in the review of the first volume and the comments then made still stand. Now that the work is finished, one may add that the Dictionary itself consists of seven volumes, page size 25 x 19 cm, with 5941 pp. in all. The 8th Volume (495 pp.) is the Index, and the 9th will be the Glossary. The price works out at about 3$d (4 cents) per page, which is on the high side. A few words on the Index may be appropriate, since it will be consulted again and again when one fails to find a particular entry immediately in the Dictionary. The Index is meant to give all reasonable variations of the terms listed in the Dictionary, as well as showing where many thousands of topics are dealt with that do not form the subject of separate articles, e.g. “Antisymmetry”, “Band
REVIEWS
Spectra”, “Band Theory”. In this respect one has the impression that it does not go far enough and it will be desirable to go through all the entries again and publish a new much enlarged edition in the future: after all, a work of this kind almost stands or falls on the ease with which it provides Referring to the above examples, information. according to the Index the concept of antisymmetry is dealt with only in the short elementary entry on the exclusion principle. It seems very probable that something more fundamental is said elsewhere. Again, while several entries are referred to under “Band theory of solids”, the most extensive (Bloch theory) is not given. r\Tophysics library can afford to be without this work. Everybody I know who has made a habit of consulting it agrees that its usefulness grows with prolonged acquaintance, and that just perusing it in a so-called idle moment can be most rewarding. Every time one finds some really outstanding contributions, models of how to convey the maximum amount of information clearly, concisely and as simply as possible. Bedford College University of London
I,. PINCIIERLE
Yr:. M. SHASHKOV(Author&d Translation from the Russian by J. E. S. BRADLEY):Metallurgy of Semiconductors. Consultants Bureau Enterprises, New York, 1960. pp. 173 $9.50. THE metallurgy of semiconductors is a subject with a short tradition. It began in 1948 with the announcement of the germanium transistor, which required the preparation of this elemental semiconductor in single crystal form with a high degree of chemical purity and structural perfection heretofore foreign to metallurgists and chemists. Today, 15 years later, this subject has broadened considerably, and is a well-defined and important branch of the rapidly growing tree of materials science. In the 173 pages of this book with its 293 references covering the period through 1957, the author attempts to survey semiconductor metallurgy by providing a compendium of metallurgical and chemical techniques applicable solely to germanium and silicon technology. The subject matter is arranged in such a manner as to take the reader essentially through a materials obstacle course in
BOOK
REVIEWS
the preparation of germanium and silicon specifically for use in transistor-like devices. This includes purification, crystal growth, techniques for outlining dislocations, incorporation of desired impurities and their diffusion and distribution coefficients, heat treatment effects, and the formation of p-n junctions. This plan is essentially a good one, but the somewhat obsolete nature of the material and the often superficial and restrictive treatment of subject matter leaves much to be desired. In reading this book, there is a constant urge to refer to the literature for significant, explanatory details. Even this is made difficult since the references, though extensive, appear not in the text but in a summary form at the beginning of each section. Hence, locating a specific contribution by a referenced author is not easy. In addition, the absence of an index in such a reference book is inexcusable. The book has 9 Chapters with 65 Figures and 16 Tables, In Chap. I, the reader is introduced to those physical, electrical and optical properties of germanium and silicon which are important to materials evaluation and to device technology. This is as it should be, but unfortunately the author does not treat this important introductory material in a satisfactory manner. First, there are no schematic diagrams illustrating phenomenologically such important concepts as electron and hole formation, injection of carriers, carrier mobility and recombination processes. Such visual aids would be most helpful to the student and beginner in this field of metallurgy. Second, the description of minority carrier lifetime is inaccurate, as are some of the density constants. These could be errors of translation which, nevertheless, are inexcusable. Finally, the optical properties are not presented in sufficient detail, being accorded only one half-page. In logical sequence Chaps. II and III discuss chemical and metallurgical methods of purifying germanium and silicon for device applications. All of the important chemical approaches are treated, and conveniently outlined by the use of flow charts. However, the text is somewhat obtuse, many statements conveying little information. It is also unfortunate that much of the data is out of date, e.g. silicon chloride reduction with hydrogen is now the standard commercial process for preparing pure silicon in this country, and not the
559
reduction of silicon tetrachloride with zinc. Also disconcerting are several errors and omissions in the referencing of chemical techniques, which again may be due in part to translation. For example, “Beketov’s process” is mentioned on several occasions, and it appears that Beketov is indeed F. M. Becket who described the zinc reduction of Sic14 in U.S. Patent 1,386,227. One also expects to find Van Arkel cited for his pioneering work in this same area, but no reference to him is found in the bibliography. Finally, the Siemens process is nowhere mentioned in connection with the author’s description of the trichlorosilane process for preparing the highest purity silicon. These errors make one cautious to accept other information with which the reader is less familiar. The metallurgical methods (Chap. III) are concerned with techniques of purification after chemical reduction. These are adequately covered by the author. They include the principles of zone refining, controlled recrystallisation by both Bridgman and Czochralski techniques, the theory of impurity distributions in solid, liquid and vapor systems, and a description of the apparatus used in these various purification techniques. In some cases the treatment is highly mathematical, and does not provide a real insight into the phenomenological processes involved. Chapter VI deals with growth of single crystals and structural defects resulting from such growth. The commonly used growth techniques, horizontal zone, Czochralski (vertical) and floating zone are presented in some detail along with the effects of such parameters as temperature gradient, growth velocity and crystal size. However, inadequate treatment is given to solution and vaporphase growth. The discussion of defects, such as twinning and dislocations, leaves much to be desired especially as regards their origin during growth, the control of their density and distribution, and their influence on properties important to both transport behavior and device fabrication. In addition, the micrographs portraying these defects are poor; and where data are presented, they are not in a definitive form. In fact, some of it is questionable. For example, it is emphasised that slip or shear is not observed on indenting germanium at temperatures up to 900°C; and indeed, there is published evidence to the contrary.
560
BOOK
REVIEWS
The effects of heat treatment on the electrical behavior of Ge and Si crystals are touched upon briefly in Chap. V, while Chaps. VI and VII are concerned with diffusion and the incorporation of impurities to produce crystals with desired electrical characteristics. Diffusion coefficients of the impurities commonly used to create electrical p-n junctions in Ge and Si are given, and methods are outlined for doping crystals both from the melt and the vapor, particularly to produce large ingots of uniform carrier concentration. So far as they go, these 3 Chapters do a fairly adequate job with the help of references which are extensive. However, it is unfortunate that the material presented is aimed too much at device applications. This tends to make the treatment too restrictive in scope as evidenced, for example, by the absence of data and discussion on solid solubility of impurities in Chaps. VI and VII. It is interesting where the two books cover the same material, HANNAY’S Semiconductors published in 1959 is both more up-to-date and technically more incisive than this book published a year later. Chapter VIII is concerned almost exclusively with techniques of creating electrical p-n junctions and regions of graded conductivity for transistorlike devices. These techniques include selective impurity additions during growth, changes in impurity distribution coefficients with growth rates, gradient melting and traveling zone involving alloying, and solid-state diffusion of impurities with different diffusion coefficients. Hence, in this Chapter, junction techniques are described which make use of principles established in earlier Chapters of the book. The same can be said of the final Chapter, which deals with etching procedures used to outline dislocations and electrical structures in devices. In summary, this work does not do justice to the broad and important science of the metallurgy of semiconductors. The book is restrictive in its scope and, as such, might more properly have been titled Metallurgy of Germanium and Silicon for Transistor Applications. But even here, the author seems to be more interested in producing a balanced history of the subject than a definitive account. Hence, it is not of general use as a text book for the student who wishes to understand the elementary aspects of a particular topic without the tedium of extensive referencing. The concept of
the book is a good one, and I only wish it had been better executed. Its chief value lies in the logical way the topics are presented. RCA Laboratories Princeton, N. J.
F. D. Rosa
J. KIIAMBATA: Introduction to Integrated Semiconductor Circuits. John Wiley, New York, 1963. pp. 219 + 8 bibliography + 5 index. $7.50.
ADI
THIS book is intended,
in the author’s own words, “to serve as an introductory guide for technical and management people in the electronics industry who are on the threshold of becoming involved in the new and fascinating field of Integrated Circuits”. Concentrating as it does on the semiconductor type of integrated circuit, only cursory attention is given the discrete component approach to microelectronics, and also relatively little attention is given to film approaches. The book is on a highly descriptive level, and appears to be written by an author highly oriented to the applications and with little or no direct experience in semiconductor integrated circuits himself. While he has learned a great deal about such circuits, the treatments do show a vagueness in certain matters which arise apparently from this lack of direct experience. On the other hand there are few if any major errors in technical matters, and the work appears to have been carefully written and edited. The work thankfully omits much of the generalized philosophy of microelectronics about which too much has already been written and said, and after an introductory section goes directly into the techniques and process of semiconductor circuits, based upon the planar technique. The treatment, while general, is adequate for the introductory purposes mentioned above, and also serves as an adequate reference for many details of the fabrication processes. The book cannot be recommended as an adequate technical survey for specialists, however, nor does the author really make any such claim. The “third section contains the meat of the book”, again to use the author’s own words, and in this section he also displays the areas of his