Williams / Poate Ion Implantation and Beam Processing

1. Auflage 2014
ISBN: 978-1-4832-2064-2
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: Adobe DRM (»Systemvoraussetzungen)

E-Book, Englisch, 432 Seiten

Ion Implantation and Beam Processing covers the scientific and technological advances in the fields of ion implantation and beam processing. The book discusses the amorphization and crystallization of semiconductors; the application of the Boltzmann transport equation to ion implantation in semiconductors and multilayer targets; and the high energy density collision cascades and spike effects. The text also describes the implantation of insulators (ices and lithographic materials); the ion-bombardment-induced compositions changes in alloys and compounds; and the fundamentals and applications of ion beam and laser mixing. The high-dose implantation and the trends of ion implantation in silicon technology are also considered. The book further tackles the implantation in gaAs technology and the contacts and interconnections on semiconductors. Engineers and people involved in microelectronics will find the book invaluable.

Autoren/Hrsg.

Williams, J. S.

Poate, J. M.

Leseproben

CHAPTER 1 Introduction to Implantation and Beam Processing
J.S. WILLIAMS,     Royal Melbourne Institute of Technology, Melbourne, Australia J.M. POATE,     Bell Laboratories, Murray Hill, New Jersey, USA Publisher Summary
This chapter presents an introduction to implantation and beam processing. Beam processing offers unique possibilities for studying fundamental aspects of crystal growth from both liquid-phase and solid-phase processes. The chapter presents an overview of beams and materials. The structure and properties of solids can be affected by radiation. There is considerable current interest in the modification of surface layers using ion, electron, and laser beams. Surfaces play a vital role in many technologies, varying from the most sophisticated, such as integrated circuit fabrication, to large-scale surface coatings. The most successful and widespread surface modification technique in semiconductor technology is ion implantation. The chapter discusses the developments in ion implantation, and related beam processing techniques using laser and electron beams. It also highlights the important amorphization and crystallization regimes in semiconductors that are accessible to the various beam-processing techniques. Irradiation of semiconductors with both energetic ions and pulsed laser beams can result in a crystalline-to-amorphous transition for process times less than about 10-9 sec, despite the fact that the energy deposition processes are very different under ion and laser irradiation conditions. I Beams and Materials II Amorphization and Crystallization III Fundamental Processes IV Semiconductor Technology and Applications I BEAMS AND MATERIALS
The structure and properties of solids can be affected by radiation. There is considerable current interest in the modification of surface layers using ion, electron and laser beams. Surfaces play a vital role in many technologies, varying from the most sophisticated, such as integrated circuit fabrication, to large-scale surface coatings. The most successful and widespread surface modification technique in semiconductor technology is ion implantation. Most integrated circuits are now fabricated using this process. Electrical dopants are introduced directly into a semiconductor surface layer by bombarding it with energetic ions. Ion implantation allows excellent control over the number and distribution of atoms that can be injected, and it is undoubtedly this feature that has made the process an indispensable part of semiconductor technology. This book deals not only with recent developments in ion implantation, but also with other, related beam processing techniques using laser and electron beams. During the past five years there has been a convergence of ideas and interests regarding these disparate techniques. Fig. 1 shows schematically the various process times. The process time can be defined as the time during which either the atoms of the solid are in motion or the solid is significantly above ambient temperatures as a result of the radiation. Energetic ions with ranges of 100 atomic layers will come to rest in ~ 10-13 sec, but the excited region created by the incident ions can persist for times of the order of 10-11 sec. Pulsed lasers, however, can be used to heat and melt surface layers in the time range 10-9 to 10-6 sec. Continuous wave lasers can be scanned over the surface layer to give processing times in the range 10-5 to 10 sec. Longer processing times can be achieved using rapid bulk heating or conventional furnaces. These various beam processing and heating techniques offer a remarkable range of processing times to the experimentalist.
Fig. 1 Processing times associated with the various beam-processing or bulk-heating techniques. Strip heaters refer to the various rapid bulk-heating techniques. The lower part of the figure shows the range of solidification processes in semiconductors. II AMORPHIZATION AND CRYSTALLIZATION
The lower half of Fig. 1 illustrates the important amorphization and crystallization regimes in semiconductors which are accessible to the various beam-processing techniques. Irradiation of semiconductors with both energetic ions and pulsed laser beams can result in a crystalline-to-amorphous transition for process times less than about 10-9 sec, despite the fact that the energy deposition processes are very different under ion and laser irradiation conditions. Processing with pulsed lasers over a longer time scale (10-9 to 10-6 sec) can result in local surface melting and rapid resolidification of the crystalline phase. The series of cross-section electron micrographs in Fig. 2 provides an excellent illustration of amorphization and liquid-phase-crystallization processes in Si. Fig. 2a shows an amorphous surface layer and a deeper band of isolated defects produced by implantation with As+ ions. Subsequent irradiation with a 30-nsec ruby laser produces the following effects. Figs. 2b and 2c illustrate that, following laser irradiation at low energy densities, an amorphous-to-polycrystalline transition occurs in the outer regions of the amorphous layer. This can be attributed to localized near-surface melting, in which the melt front did not extend into the underlying crystal. Figs. 2d and 2e show an amorphous-to-single crystal transition in which the melt has just penetrated into the underlying crystal during the laser irradiation and then resolidified from the bulk seed crystal towards the surface. Irradiation at a higher energy density (Fig. 2f), which induces melting beyond the region of isolated defects, produces extended-defect-free single crystal via liquid phase epitaxial growth. The entire melting and recrystallization process occurs in a time of less than 100 nsec. Details of such rapid amorphization and crystallization processes are described in detail in Chapter 2.
Fig. 2 Transmission electron microscope (TEM) cross-sectional images of an ion-implanted (150 keV As+, 4 × 1015 cm-2) amorphous layer on (100) Si. The first image (a) shows the as-implanted layer and the following images (b–f) show deeper melt depths using a pulsed ruby laser (30 nsec); (b) 0.2 J cm-2; (c) 0.35 J cm-2; (d) 0.85 J cm-2; (e) 1.0 J cm-2; and (f) 1.2 J cm-2. In “Laser Annealing of Semiconductors” (J. M. Poate and J. W. Mayer, eds.), Academic Press, New York. From A. G. Cullis (1982). Heating by continuous wave (cw) lasers, by rapid bulk heating and by conventional furnace processes, for times greater than about 10-5 sec, can produce an amorphous-to-crystalline transition via crystal growth within the solid phase. These various amorphization-crystallization regimes have important fundamental and technological consequences for beam processing of semiconductors. In Chapter 2, Poate and Williams give an overview of the damage and amorphization processes in semiconductors which are induced by ion implantation, and they review the use of solid-phase and liquid-phase annealing methods to subsequently remove this damage. Indeed, for electronic-device applications, it is vital to follow the implantation process with an annealing step in order to reconstitute the crystal lattice and incorporate the implanted dopant atoms into electrically active lattice sites. Beam processing over the time spans illustrated in Fig. 1 offers unique possibilities for studying fundamental aspects of crystal growth from both liquid-phase and solid-phase processes. As discussed in Chapter 2, the ability of implantation to produce “clean” amorphous layers has led to recrystallization studies using a range of both beam-processing techniques and more conventional annealing techniques. These have provided new insights into the mechanisms of crystal growth and have allowed fundamental thermodynamic parameters to be measured directly. In particular, non-equilibrium conditions of crystal growth can result in the production of metastable solid solutions. III FUNDAMENTAL PROCESSES
Much of this book is concerned with the ion implantation process and, in particular, with those aspects, both fundamental and technological, which constitute current research and development. However, it is important to review briefly the fundamental ion implantation processes so that the topics of both current research interest (Chapters 2 to 8) and current applications (Chapters 5, 8 to 11) may be given a proper perspective. The four basic processes which directly result from ion bombardment are illustrated schematically in Figs. 3 and 4. As depicted by the ion trajectory in Fig. 3, a single ion of keV energies undergoes a series of energy-loss collisions with both target atoms (nuclear collisions) and electrons (electronic collisions), finally coming to rest some hundreds of atom layers below the surface. When many mono-energetic ions are implanted, the statistical nature of nuclear and...