Dopant redistribution in silicide–silicon and silicide–polycrystalline silicon bilayered structures

Abstract

Dopants in any layer of the silicide–silicon or silicide–polycrystalline silicon bilayer structures are found to distribute readily throughout the bilayer affecting the electrical and the mechanical properties of the composite. In this paper the phenomenon of dopant redistribution in such structures is reviewed. The factors that influence the redistribution processes are (a) the diffusivity of dopants in the structure; (b) the solid solubility of dopants in the silicide and in the silicon; (c) the segregation coefficient of dopant at the surface and at the interfaces, and (d) the evaporative or the reactive losses of dopant to the heat-treating environment. Each of these factors is discussed. The available experimental results are reviewed in view of these considerations. It is shown that there are a large number of variables and that the available experimental results only provide a technological base for the use of dopants in the structures studied. To obtain a fundamental understanding of the process that determines the dopant redistribution, more carefully planned experiments will be necessary.