The motion of energetic charged particles inside a monocrystalline solid can be strongly influenced by channeling and blocking effects. The present article reviews the theory, the experimental studies, and some of the applications of these effects. The coverage of the published literature extends through June 1973.

Channeling and related effects in the motion of charged particles through crystals

Publisher Summary A refractive index can be increased by ion implantation by changes in density and structure, by the addition of high-polarizability impurity ions, by a reduction of the plasma effect that increases the index and that is most important in the wavelength region far from the energy gap, and by absorption changing in the index in the region of the gap, that is, via the Kramers–Kronig relation. This chapter discusses the optical properties of implanted semiconductors, electrooptic components formed by ion implantation, general principles that determine most luminescent systems, effects of implantation temperature, luminescence centers in LiF-Mg-Ti radiation dosimeters, and use of line spectra in defect studies. In the LiF system, the luminescence bands are broad, and if alternative versions of the same complex exist, they cannot be resolved from the spectra. The addition, by implantation, of ions with incomplete inner electron shells opens up new possibilities as the lattice distortions of the free-ion energy levels are strongly perturbed by the defects in the neighborhood of the ion.

Optical Effects of Ion Implantation

Radiation damage is produced in a crystalline target whenever a moving ion transfers sufficient energy to a target atom to displace it from its lattice site. For conditions of practical importance in ion implantation, the radiation damage produced by the injected ions is severe, and the crystal must be carefully Annealed if the chemical effects of the implanted ions are to dominate the residual damage. The purpose of this paper is to review work that has been performed over the past several years in an effort to understand implantation-produced damage and its annealing characteristics, especially in silicon. The subject is developed as follows. A qualitative description of the damage produced by an implanted ion is presented in Section I, followed by a partial inventory of the basic defects that are found in ion-implanted silicon (Section II). The structure of individual damage clusters produced by both heavy and light ions is then described in Section III, where theoretical predictions are compared to a variety of experimental data. This is followed with a section on the depth distribution of defects and damage clusters (Section IV); and the paper is then concluded with a section on the annealing characteristics of implantation-produced damage (Section V). The development is organized to give primary emphasis to those facts and ideas that are essential for applications of ion implantation in the fabrication of MOS and junction devices in silicon. A future paper will review the state of the art in compound semiconductors.

Ion implantation in semiconductors&#8212;Part II: Damage production and annealing

The spatial distribution of sputter-etch effects is analysed theoretically under the assumption of random slowing-down of the bombarding ions. When a surface is bombarded at locally oblique incidence the most pronounced sputtering effect is likely to be observed not at the very point of impact, but further “downstream”. This effect may cause a significant reduction of the local sputtering yield on top of a spike or a ridge, and an increase on the bottom of a groove or a crater. As a consequence, small irregularities on a relatively smooth surface may be enhanced during bombardment. It is concluded that a microscopically flat surface is unstable under high-dose ion bombardment unless atom migration acts as a dominating smoothing effect. Conversely, sharp cones appear to be surprisingly stable under bombardment. Even on a clean surface, cones erode more slowly than a plane surface, provided that their dimensions are of the order of, or less than, the penetration depth of the ions.

A mechanism of surface micro-roughening by ion bombardment

Sputtering by ion bombardment theoretical concepts

Channeling effects on the yield of large angle backscattered energetic H+ or He+ were used to investigate properties of the disorder in Si samples previously implanted with B11 ions at substrate temperatures of -150°C to -50°C. Exposure of the implanted samples to the analyzing beam at room temperature caused a large reduction in the amount of disorder measured. A successive layer removal technique by anodic oxidation and stripping was used to obtain a depth scale for 1.8 MeVHe+ analyses of lightly disordered samples. The results of additional experiments indicate that for 1 MeV He+ in Si the aligned stopping power is about 80 per cent of the random stopping power. Measured and calculated values of the minimum yield X R for the substrate underlying amorphous layers suggested a plural scattering treatment of dechanneling of the analyzing beam using previously measured values of the critical angle. The scattering center distributions calculated from this treatment of dechanneling are presented for ...

Analysis of disorder distributions in boron implanted silicon

Simple depth distribution functions of ion bombardment damage predict the spatial extension of the cumulative damage caused by a beam of ions. Correlation functions need to be considered when more detailed information is desirable, such as the average size or depth of individual damage clusters, the average location of an ion within its damage cluster, and the fluctuations of these quantities. In this paper we establish an integral equation for the pair correlation function, coupling the individual ion range with the deposited energy. This pair correlation function determines the damage caused by all those ions that come to rest at a specific penetration depth. Solutions of the integral equation are found by standard methods. Explicit results are presented for elastic scattering governed by power cross sections. The depth distribution of damage clusters turns out to be significantly narrower than the gross damage distribution at all mass ratios except for M 1 ≪ M 2, and the size distribution appe...

Correlation functions in the theory of atomic collision cascades: Ion location and the distribution in depth and size of damage clusters

We have investigated the lattice disorder produced in Si by 200‐keV B implantations using the standard channeling technique. We found the disorder production strongly temperature‐dependent from about −85°C to room temperature. The annealing of the residual disorder present after such a B implantation takes place at higher temperatures. Our results indicate that the nature of the lattice disorder produced in Si by low dose ion implantation depends on the mass of the ion implanted.

Production and Annealing of Lattice Disorder in Silicon by 200-keV Boron Ions

We have used the standard channeling technique with a 1.0 MeV He+ analyzing beam to investigate the lattice disorder produced in GaAs by 60 keV Cd and 70 keV Zn ion implantations made at room temperature. The amount of disorder produced increases linearly with dose and saturates at a dose of approximately 1–2 × 1013 Cd ions/cm2. The disorder present in low dose implants (∼5 × 1012 Cd ions/cm2) anneals appreciably by 150 °C. With increasing doses of Cd or Zn the samples show a continuous increase in the anneal temperature required to remove a substantial amount of lattice disorder. There is no apparent difference between the anneal of Zn and Cd implants. The rate at which lattice disorder is produced in GaAs by heavy ion implantations and the doses of heavy ions required to saturate the lattice disorder observed are significantly different from the values of the corresponding quantities for Si and Ge.

J. E. Westmoreland

Papers

Analysis of disorder distributions in boron implanted silicon

Correlation functions in the theory of atomic collision cascades: Ion location and the distribution in depth and size of damage clusters

Production and Annealing of Lattice Disorder in Silicon by 200-keV Boron Ions

LATTICE DISORDER PRODUCED IN GaAs BY 60-keV Cd IONS AND 70-keV Zn IONS.

Lattice disorder produced in silicon by boron-ion implantation.