Microdevices – serie

GaAs devices and integrated circuits have emerged as leading contenders for ultra-high-speed applications. This book is intended to be a reference for a rapidly growing GaAs community of researchers and graduate students. It was written over several years and parts of it were used for courses on GaAs devices and integrated circuits and on heterojunction GaAs devices developed and taught at the University of Minnesota. Many people helped me in writing this book. I would like to express my deep gratitude to Professor Lester Eastman of Cornell University, whose ideas and thoughts inspired me and helped to determine the direction of my research work for many years. I also benefited from numerous discussions with his students and associates and from the very atmosphere of the pursuit of excellence which exists in his group. I would like to thank my former and present co-workers and colleagues-Drs. Levinstein and Gelmont of the A. F. Ioffe Institute of Physics and Technology, Professor Melvin Shaw of Wayne State University, Dr. Kastalsky of Bell Communi­ cations, Professor Gary Robinson of Colorado State University, Professor Tony Valois, and Dr. Tim Drummond of Sandia Labs-for their contributions to our joint research and for valuable discussions. My special thanks to Professor Morko.;, for his help, his ideas, and the example set by his pioneering work. Since 1978 I have been working with engineers from Honeywell, Inc.-Drs.

Present-day scienceand technology have become increasingly based on studies and applications of thin films. This is especiallytrue of solid-state physics, semiconduc­ tor electronics, integrated optics, computer science, and the like. In these fields, it is necessary to use filmswith an ordered structure, especiallysingle-crystallinefilms, because physical phenomena and effects in such films are most reproducible. Also, active parts of semiconductor and other devices and circuits are created, as a rule, in single-crystal bodies. To date, single-crystallinefilms have been mainly epitaxial (or heteroepitaxial); i.e., they have been grown on a single-crystalline substrate, and principal trends, e.g., in the evolution of integrated circuits (lCs), have been based on continuing reduction in feature size and increase in the number of components per chip. However, as the size decreases into the submicrometer range, technological and physical limitations in integrated electronics become more and more severe. It is generally believed that a feature size of about 0.1um will have a crucial character. In other words, the present two-dimensional ICs are anticipated to reach their limit of minimization in the near future, and it is realized that further increase of packing density and/or functions might depend on three-dimensional integration. To solve the problem, techniques for preparation of single-crystalline films on arbitrary (including amorphous) substrates are essential.

This book is devoted to the physics of electron-beam, ion-beam, optical, and x-ray lithography. The need for this book results from the following considerations. The astonishing achievements in microelectronics are in large part connected with successfully applying the relatively new technology of processing (changing the prop­ erties of) a material into a device whose component dimensions are submicron, called photolithography. In this method the device is imaged as a pattern on a metal film that has been deposited onto a transparent substrate and by means of a broad stream of light is transferred to a semiconductor wafer within which the physical structure of the devices and the integrated circuit connections are formed layer by layer. The smallest dimensions of the device components are limited by the diffraction of the light when the pattern is transferred and are approximately the same as the wavelength of the light. Photolithography by light having a wavelength of A ~ 0.4 flm has made it possible to serially produce integrated circuits having devices whose minimal size is 2-3 flm in the 4 pattern and having 10-105 transistors per circuit.

In this revised and expanded edition, the authors provide a comprehensive overview of the tools, technologies, and physical models needed to understand, build, and analyze microdevices. Students, specialists within the field, and researchers in related fields will appreciate their unified presentation and extensive references.

Although exploratory and developmental activity in electron beam testing (EBT) 25 years, it was not had already been in existence in research laboratories for over until the beginning of the 1980s that it was taken up seriously as a technique for integrated circuit (IC) testing. While ICs were being fabricated on design rules of several microns, the mechanical ne edle probe served quite adequately for internal chip probing. This scenario changed with growing device complexity and shrinking geometries, prompting IC manufacturers to take note ofthis new testing technology. It required several more years and considerable investment by electron beam tester manufacturers, however, to co me up with user-friendly automated systems that were acceptable to IC test engineers. These intervening years witnessed intense activity in the development of instrumentation, testing techniques, and system automation, as evidenced by the proliferation of technical papers presented at conferences. With the shift of interest toward applications, the technology may now be considered as having come of age.

In recent years, III-V devices, integrated circuits, and superconducting integrated circuits have emerged as leading contenders for high-frequency and ultrahigh­ speed applications. GaAs MESFETs have been applied in microwave systems as low-noise and high-power amplifiers since the early 1970s, replacing silicon devices. The heterojunction high-electron-mobility transistor (HEMT), invented in 1980, has become a key component for satellite broadcasting receiver systems, serving as the ultra-low-noise device at 12 GHz. Furthermore, the heterojunction bipolar transistor (HBT) has been considered as having the highest switching speed and cutoff frequency in the semiconductor device field. Initially most of these devices were used for analog high-frequency applications, but there is also a strong need to develop high-speed III-V digital devices for computer, telecom­ munication, and instrumentation systems, to replace silicon high-speed devices, because of the switching-speed and power-dissipation limitations of silicon. The potential high speed and low power dissipation of digital integrated circuits using GaAs MESFET, HEMT, HBT, and superconducting Josephson junction devices has evoked tremendous competition in the race to develop such technology. A technology review shows that Japanese research institutes and companies have taken the lead in the development of these devices, and some integrated circuits have already been applied to supercomputers in Japan. The activities of Japanese research institutes and companies in the III-V and superconducting device fields have been superior for three reasons. First, bulk crystal growth, epitaxial growth, process, and design technology were developed at the same time.

This book examines the physical principles behind the operation of high-speed transistors operating at frequencies above 10 GHz and having switching times less than 100 psec. If the 1970s cannot be remembered for the opportunities for creating and extensively using transistors operating at such high speeds, then, the situation has changed radically because of rapid progress in sub micrometer technology for manufacturing transistors and integrated circuits from GaAs and other semiconductor materials and the powerful influx of new physical concepts. Not only have transistors having switching speeds of 50-100 psec operating in the 10-20 GHz region been created in recent years, but the possibilities for manufacturing transistors operating one to two orders of magnitude faster have been revealed. As superhigh-speed transistors have been created, many of the most important areas of technology such as communications, computing technology, television, radar, and the manufacture of scientific, industrial, and medical equipment have qualitatively changed. Microwave transistors operating at millimeter wavelengths make it possible to produce compact and highly efficient equipment for communications and radar technology. Transistors with switching speeds better than 10-100 psec make it possible to increase the speed of microprocessors and other computer components to tens of billions of operations per second and thereby solve one of the most pressing problems of modern electronics - increasing the speed of digital information processing.

Rapid thermal processing has contributed to the development of single wafer cluster processing tools and other innovations in integrated circuit manufacturing environments. Borisenko and Hesketh review theoretical and experimental progress in the field, discussing a wide range of materials, processes, and conditions. They thoroughly cover the work of international investigators in the field.

The advent of the microelectronics technology has made ever-increasing numbers of small devices on a same chip. The rapid emergence of ultra-large-scaled-integrated (ULSI) technology has moved device dimension into the sub-quarter-micron regime and put more than 10 million transistors on a single chip. While traditional closed-form analytical models furnish useful intuition into how semiconductor devices behave, they no longer provide consistently accurate results for all modes of operation of these very small devices. The reason is that, in such devices, various physical mechanisms affect the device performance in a complex manner, and the conventional assumptions (i. e. , one-dimensional treatment, low-level injection, quasi-static approximation, etc. ) em­ ployed in developing analytical models become questionable. Thus, the use of numerical device simulation becomes important in device modeling. Researchers and engineers will rely even more on device simulation for device design and analysis in the future. This book provides comprehensive coverage of device simulation and analysis for various modem semiconductor devices. It will serve as a reference for researchers, engineers, and students who require in-depth, up-to-date information and understanding of semiconductor device physics and characteristics. The materials of the book are limited to conventional and mainstream semiconductor devices; photonic devices such as light­ emitting and laser diodes are not included, nor does the book cover device modeling, device fabrication, and circuit applications.

Field emission is a phenomenon described by quantum mechanics. Its emission capability is millions times higher than that of any other known types of electron emission. Nowadays this phenomenon is experiencing a new life due to wonderful applications in the atomic resolution microscopy, in electronic holography, and in the vacuum micro- and nanoelectronics in general. The main field emission properties, and some most remarkable experimental facts and applications, are described in this book.

Narrow gap semiconductors obey the general rules of semiconductor science, but often exhibit extreme features of these rules because of the same properties that produce their narrow gaps. Consequently, these materials provide sensitive tests of theory, and the opportunity for the design of innovative devices. For example, narrow gap semiconductors are the most important materials for the preparation of advanced modern infrared systems. In this book, the authors offer clear descriptions of crystal growth and the fundamental structure and properties of these unique materials. Topics covered include band structure, optical and transport properties, and lattice vibrations and spectra. A thorough treatment of the properties of low-dimensional systems and their relation to infrared applications is provided. In addition to covering the technology of photoconductive detectors, photovoltaic detectors, metal-insulator-semiconductor devices, quantum well infrared photodetectors, infrared lasers, and single photon detectors, Physics and Properties of Narrow Gap Semiconductors helps readers to understand semiconductor physics and related areas of materials science and how they relate to advanced opto-electronic devices.

Narrow gap semiconductors obey the general rules of semiconductor science, but often exhibit extreme features of these rules because of the same properties that produce their narrow gaps. Consequently these materials provide sensitive tests of theory, and the opportunity for the design of innovative devices. Narrow gap semiconductors are the most important materials for the preparation of advanced modern infrared systems.Device Physics of Narrow Gap Semiconductors, a forthcoming second book, offers descriptions of the materials science and device physics of these unique materials. Topics covered include impurities and defects, recombination mechanisms, surface and interface properties, and the properties of low dimensional systems for infrared applications. This book will help readers to understand not only semiconductor physics and materials science, but also how they relate to advanced opto-electronic devices. The final chapter describes the device physics of photoconductive detectors, photovoltaic infrared detectors, super lattices and quantum wells, infrared lasers, and single photon infrared detectors.

Narrow gap semiconductors obey the general rules of semiconductor science, but often exhibit extreme features of these rules because of the same properties that produce their narrow gaps. Consequently, these materials provide sensitive tests of theory, and the opportunity for the design of innovative devices. For example, narrow gap semiconductors are the most important materials for the preparation of advanced modern infrared systems. In this book, the authors offer clear descriptions of crystal growth and the fundamental structure and properties of these unique materials. Topics covered include band structure, optical and transport properties, and lattice vibrations and spectra. A thorough treatment of the properties of low-dimensional systems and their relation to infrared applications is provided. In addition to covering the technology of photoconductive detectors, photovoltaic detectors, metal-insulator-semiconductor devices, quantum well infrared photodetectors, infrared lasers, and single photon detectors, Physics and Properties of Narrow Gap Semiconductors helps readers to understand semiconductor physics and related areas of materials science and how they relate to advanced opto-electronic devices.

In this revised and expanded edition, the authors provide a comprehensive overview of the tools, technologies, and physical models needed to understand, build, and analyze microdevices. Students, specialists within the field, and researchers in related fields will appreciate their unified presentation and extensive references.

Field emission is a phenomenon described by quantum mechanics. Its emission capability is millions times higher than that of any other known types of electron emission. Nowadays this phenomenon is experiencing a new life due to wonderful applications in the atomic resolution microscopy, in electronic holography, and in the vacuum micro- and nanoelectronics in general. The main field emission properties, and some most remarkable experimental facts and applications, are described in this book.

The purpose of this book is to provide the reader with a self-contained treatment of fundamen­ tal solid state and semiconductor device physics. The material presented in the text is based upon the lecture notes of a one-year graduate course sequence taught by this author for many years in the ·Department of Electrical Engineering of the University of Florida. It is intended as an introductory textbook for graduate students in electrical engineering. However, many students from other disciplines and backgrounds such as chemical engineering, materials science, and physics have also taken this course sequence, and will be interested in the material presented herein. This book may also serve as a general reference for device engineers in the semiconductor industry. The present volume covers a wide variety of topics on basic solid state physics and physical principles of various semiconductor devices. The main subjects covered include crystal structures, lattice dynamics, semiconductor statistics, energy band theory, excess carrier phenomena and recombination mechanisms, carrier transport and scattering mechanisms, optical properties, photoelectric effects, metal-semiconductor devices, the p--n junction diode, bipolar junction transistor, MOS devices, photonic devices, quantum effect devices, and high­ speed III-V semiconductor devices. The text presents a unified and balanced treatment of the physics of semiconductor materials and devices. It is intended to provide physicists and mat­ erials scientists with more device backgrounds, and device engineers with a broader knowledge of fundamental solid state physics.

Semiconductor lithography is one of the key steps in the manufacturing of integrated silicon-based circuits. In fabricating a semiconductor device such as a transistor, a series of hot processes consisting of vacuum film deposition, oxidations, and dopant implantation are all patterned into microscopic circuits by the wet processes of lithography. Lithography, as adopted by the semiconductor industry, is the process of drawing or printing the pattern of an integrated circuit in a resist material. The pattern is formed and overlayed to a previous circuit layer as many as 30 times in the manufacture of logic and memory devices. With the resist pattern acting as a mask, a permanent device structure is formed by subtractive (removal) etching or by additive deposition of metals or insulators. Each process step in lithography uses inorganic or organic materials to physically transform semiconductors of silicon, insulators of oxides, nitrides, and organic polymers, and metals, into useful electronic devices. All forms of electromagnetic radiation are used in the processing. Lithography is a mUltidisciplinary science of materials, processes, and equipment, interacting to produce three-dimensional structures. Many aspects of chemistry, electrical engineering, materials science, and physics are involved. The purpose of this book is to bring together the work of many scientists and engineers over the last 10 years and focus upon the basic resist materials, the lithographic processes, and the fundamental principles behind each lithographic process.

The field of electron and ion optics is based on the analogy between geometrical light optics and the motion of charged particles in electromagnetic fields. The spectacular development of the electron microscope clearly shows the possibilities of image formation by charged particles of wavelength much shorter than that of visible light. As new applications such as particle accelerators, cathode ray tubes, mass and energy spectrometers, microwave tubes, scanning-type analytical instruments, heavy beam technologies, etc. emerged, the scope of particle beam optics has been exten­ ded to the formation of fine probes. The goal is to concentrate as many particles as possible in as small a volume as possible. Fabrication of microcircuits is a good example of the growing importance of this field. The current trend is towards increased circuit complexity and pattern density. Because of the diffraction limitation of processes using optical photons and the technological difficulties connected with x-ray processes, charged particle beams are becoming popular. With them it is possible to write directly on a wafer under computer control, without using a mask. Focused ion beams offer especially great possibilities in the submicron region. Therefore, electron and ion beam technologies will most probably playa very important role in the next twenty years or so.

The purposes of this book are many. First, we must point out that it is not a device book, as a proper treatment of the range of important devices would require a much larger volume even without treating the important physics for submicron devices. Rather, the book is written principally to pull together and present in a single place, and in a (hopefully) uniform treatment, much of the understanding on relevant physics for submicron devices. Indeed, the understand­ ing that we are trying to convey through this work has existed in the literature for quite some time, but has not been brought to the full attention of those whose business is the making of submicron devices. It should be remarked that much of the important physics that is discussed here may not be found readily in devices at the 1.0-JLm level, but will be found to be dominant at the O.I-JLm level. The range between these two is rapidly being covered as technology moves from the 256K RAM to the 16M RAM chips.

This book is devoted to the physics of electron-beam, ion-beam, optical, and x-ray lithography. The need for this book results from the following considerations. The astonishing achievements in microelectronics are in large part connected with successfully applying the relatively new technology of processing (changing the prop­ erties of) a material into a device whose component dimensions are submicron, called photolithography. In this method the device is imaged as a pattern on a metal film that has been deposited onto a transparent substrate and by means of a broad stream of light is transferred to a semiconductor wafer within which the physical structure of the devices and the integrated circuit connections are formed layer by layer. The smallest dimensions of the device components are limited by the diffraction of the light when the pattern is transferred and are approximately the same as the wavelength of the light. Photolithography by light having a wavelength of A ~ 0.4 flm has made it possible to serially produce integrated circuits having devices whose minimal size is 2-3 flm in the 4 pattern and having 10-105 transistors per circuit.

In the first comprehensive treatment of these technologically important materials, the authors provide theories linking the properties of semiconductor alloys to their constituent compounds. Topics include crystal structures, bonding, elastic properties, phase diagrams, band structures, transport, ab-initio theories, and semi-empirical theories. Each chapter includes extensive tables and figures as well as problem sets.

Narrow gap semiconductors obey the general rules of semiconductor science, but often exhibit extreme features of these rules because of the same properties that produce their narrow gaps. Consequently these materials provide sensitive tests of theory, and the opportunity for the design of innovative devices. Narrow gap semiconductors are the most important materials for the preparation of advanced modern infrared systems.Device Physics of Narrow Gap Semiconductors, a forthcoming second book, offers descriptions of the materials science and device physics of these unique materials. Topics covered include impurities and defects, recombination mechanisms, surface and interface properties, and the properties of low dimensional systems for infrared applications. This book will help readers to understand not only semiconductor physics and materials science, but also how they relate to advanced opto-electronic devices. The final chapter describes the device physics of photoconductive detectors, photovoltaic infrared detectors, super lattices and quantum wells, infrared lasers, and single photon infrared detectors.

The technological progress is closely related to the developments of various materials and tools made of those materials. Even the different ages have been defined in relation to the materials used. Some of the major attributes of the present-day age (i.e., the electronic materials’ age) are such common tools as computers and fiber-optic telecommunication systems, in which semiconductor materials provide vital components for various mic- electronic and optoelectronic devices in applications such as computing, memory storage, and communication. The field of semiconductors encompasses a variety of disciplines. This book is not intended to provide a comprehensive description of a wide range of semiconductor properties or of a continually increasing number of the semiconductor device applications. Rather, the main purpose of this book is to provide an introductory perspective on the basic principles of semiconductor materials and their applications that are described in a relatively concise format in a single volume. Thus, this book should especially be suitable as an introductory text for a single course on semiconductor materials that may be taken by both undergraduate and graduate engineering students. This book should also be useful, as a concise reference on semiconductor materials, for researchers working in a wide variety of fields in physical and engineering sciences.

In recent years, III-V devices, integrated circuits, and superconducting integrated circuits have emerged as leading contenders for high-frequency and ultrahigh­ speed applications. GaAs MESFETs have been applied in microwave systems as low-noise and high-power amplifiers since the early 1970s, replacing silicon devices. The heterojunction high-electron-mobility transistor (HEMT), invented in 1980, has become a key component for satellite broadcasting receiver systems, serving as the ultra-low-noise device at 12 GHz. Furthermore, the heterojunction bipolar transistor (HBT) has been considered as having the highest switching speed and cutoff frequency in the semiconductor device field. Initially most of these devices were used for analog high-frequency applications, but there is also a strong need to develop high-speed III-V digital devices for computer, telecom­ munication, and instrumentation systems, to replace silicon high-speed devices, because of the switching-speed and power-dissipation limitations of silicon. The potential high speed and low power dissipation of digital integrated circuits using GaAs MESFET, HEMT, HBT, and superconducting Josephson junction devices has evoked tremendous competition in the race to develop such technology. A technology review shows that Japanese research institutes and companies have taken the lead in the development of these devices, and some integrated circuits have already been applied to supercomputers in Japan. The activities of Japanese research institutes and companies in the III-V and superconducting device fields have been superior for three reasons. First, bulk crystal growth, epitaxial growth, process, and design technology were developed at the same time.

This book examines the physical principles behind the operation of high-speed transistors operating at frequencies above 10 GHz and having switching times less than 100 psec. If the 1970s cannot be remembered for the opportunities for creating and extensively using transistors operating at such high speeds, then, the situation has changed radically because of rapid progress in sub micrometer technology for manufacturing transistors and integrated circuits from GaAs and other semiconductor materials and the powerful influx of new physical concepts. Not only have transistors having switching speeds of 50-100 psec operating in the 10-20 GHz region been created in recent years, but the possibilities for manufacturing transistors operating one to two orders of magnitude faster have been revealed. As superhigh-speed transistors have been created, many of the most important areas of technology such as communications, computing technology, television, radar, and the manufacture of scientific, industrial, and medical equipment have qualitatively changed. Microwave transistors operating at millimeter wavelengths make it possible to produce compact and highly efficient equipment for communications and radar technology. Transistors with switching speeds better than 10-100 psec make it possible to increase the speed of microprocessors and other computer components to tens of billions of operations per second and thereby solve one of the most pressing problems of modern electronics - increasing the speed of digital information processing.

Although exploratory and developmental activity in electron beam testing (EBT) 25 years, it was not had already been in existence in research laboratories for over until the beginning of the 1980s that it was taken up seriously as a technique for integrated circuit (IC) testing. While ICs were being fabricated on design rules of several microns, the mechanical ne edle probe served quite adequately for internal chip probing. This scenario changed with growing device complexity and shrinking geometries, prompting IC manufacturers to take note ofthis new testing technology. It required several more years and considerable investment by electron beam tester manufacturers, however, to co me up with user-friendly automated systems that were acceptable to IC test engineers. These intervening years witnessed intense activity in the development of instrumentation, testing techniques, and system automation, as evidenced by the proliferation of technical papers presented at conferences. With the shift of interest toward applications, the technology may now be considered as having come of age.

Rapid thermal processing has contributed to the development of single wafer cluster processing tools and other innovations in integrated circuit manufacturing environments. Borisenko and Hesketh review theoretical and experimental progress in the field, discussing a wide range of materials, processes, and conditions. They thoroughly cover the work of international investigators in the field.

The advent of the microelectronics technology has made ever-increasing numbers of small devices on a same chip. The rapid emergence of ultra-large-scaled-integrated (ULSI) technology has moved device dimension into the sub-quarter-micron regime and put more than 10 million transistors on a single chip. While traditional closed-form analytical models furnish useful intuition into how semiconductor devices behave, they no longer provide consistently accurate results for all modes of operation of these very small devices. The reason is that, in such devices, various physical mechanisms affect the device performance in a complex manner, and the conventional assumptions (i. e. , one-dimensional treatment, low-level injection, quasi-static approximation, etc. ) em­ ployed in developing analytical models become questionable. Thus, the use of numerical device simulation becomes important in device modeling. Researchers and engineers will rely even more on device simulation for device design and analysis in the future. This book provides comprehensive coverage of device simulation and analysis for various modem semiconductor devices. It will serve as a reference for researchers, engineers, and students who require in-depth, up-to-date information and understanding of semiconductor device physics and characteristics. The materials of the book are limited to conventional and mainstream semiconductor devices; photonic devices such as light­ emitting and laser diodes are not included, nor does the book cover device modeling, device fabrication, and circuit applications.

GaAs devices and integrated circuits have emerged as leading contenders for ultra-high-speed applications. This book is intended to be a reference for a rapidly growing GaAs community of researchers and graduate students. It was written over several years and parts of it were used for courses on GaAs devices and integrated circuits and on heterojunction GaAs devices developed and taught at the University of Minnesota. Many people helped me in writing this book. I would like to express my deep gratitude to Professor Lester Eastman of Cornell University, whose ideas and thoughts inspired me and helped to determine the direction of my research work for many years. I also benefited from numerous discussions with his students and associates and from the very atmosphere of the pursuit of excellence which exists in his group. I would like to thank my former and present co-workers and colleagues-Drs. Levinstein and Gelmont of the A. F. Ioffe Institute of Physics and Technology, Professor Melvin Shaw of Wayne State University, Dr. Kastalsky of Bell Communi­ cations, Professor Gary Robinson of Colorado State University, Professor Tony Valois, and Dr. Tim Drummond of Sandia Labs-for their contributions to our joint research and for valuable discussions. My special thanks to Professor Morko.;, for his help, his ideas, and the example set by his pioneering work. Since 1978 I have been working with engineers from Honeywell, Inc.-Drs.