Papers by Keyword: Dissociative Mechanism

Abstract: Elemental semiconductors play an important role in high-technology equipment used in industry and everyday life. The first transistors were made in the 1950ies of germanium. Later silicon took over because its electronic band-gap is larger. Nowadays, germanium is the base material mainly for γ-radiation detectors. Silicon is the most important semiconductor for the fabrication of solid-state electronic devices (memory chips, processors chips, ...) in computers, cellphones, smartphones. Silicon is also important for photovoltaic devices of energy production.Diffusion is a key process in the fabrication of semiconductor devices. This chapter deals with diffusion and point defects in silicon and germanium. It aims at making the reader familiar with the present understanding rather than painstakingly presenting all diffusion data available a good deal of which may be found in a data collection by Stolwijk and Bracht [1], in the author’s textbook [2], and in recent review papers by Bracht [3, 4]. We mainly review self-diffusion, diffusion of doping elements, oxygen diffusion, and diffusion modes of hybrid foreign elements in elemental semiconductors.Self-diffusion in elemental semiconductors is a very slow process compared to metals. One of the reasons is that the equilibrium concentrations of vacancies and self-interstitials are low. In contrast to metals, point defects in semiconductors exist in neutral and in charged states. The concentrations of charged point defects are therefore affected by doping [2 - 4].

Abstract: The study of fast diffusion processes in materials requires short isothermal annealing treatments combined with an accurate temperature measurement. The paper discusses the special demands on rapid thermal annealing (RTA) devices in diffusion research and how these can be met in practice. The scientific impact of RTA for diffusion research in semiconductors is demonstrated by several examples dealing with fast impurities in Ge and Si.

Abstract: The analytical treatment of dissociative diffusion by using the matched perturbation method given in the literature deals with a virtually infinite foreign-atom source producing a constant^concentration at the boundary. In this paper, a new mathematical model is developed for analysing the dissociative diffusion of the solute atoms in the case of finite-source conditions. The mathematical model combines the reaction-diffusion equations which govern solute atom diffusion by the dissociative mechanism and the boundary condition expressing the fact that the rate at which solute leaves the source is always equal to that at which it enters the sheet over the surface x=0. Solutions obtained by applying the matched perturbation method and their comparison with those of the numerical study are also presented in this paper.

Abstract: In this work we develop an analytical method for resolution of the reaction-diffusion equations which govern impurity diffusion by the dissociative mechanism in a finite-thickness sample and from a deposit of solute atoms on the surface. This method is based upon the perturbation of basic solutions corresponding to limiting cases and the choice of suitable small parameters. The solutions obtained and their comparison to those of numerical studies are also presented in this paper.