Transition Metal Silicides

Abstract

There are several review papers written on transition metal silicides, which have attracted considerable attention in recent years because of their potential usefulness in silicon integrated circuits (SICs) (1-7). Aronsson et al (1) critically reviewed the preparation, properties, and crystal chemistry in their book Borides, Silicides and Phosphides. Wehrmann (2) emphasized the high-temperature behavior of the silicides formed by using powder metallurgical techniques. Van Gurp (3), Tu & Mayer (4), and Ottaviani (5) reviewed the thin-film silicides formed by reaction between thin films and between thin films and substrates. Murarka (6) and Mohammadi (7) considered the silicides for application in SICs. Most of the silicide research, performed from the beginning of this century through the 1960s, used powder metallurgical techniques to produce silicides. These studies revealed the silicide properties such as electrical resistivities, high-temperature stability, corrosion resistance, and, most important of all, the silicide crystal chemistry and metal-silicon phase diagrams. The possibility of using silicides as conductors [as Schottky barriers and contacts (8, 9) and as gate and interconnection metallization (10)] in SICs motivated thin-film silicide research. Besides the measure­ ments of Schottky barrier heights and resistivities, the intermetallic formation in the metal-silicon systems, reaction and interdiffusion kinetics, stability at the SIC processing and operating temperatures, mechanical stability, oxidation and etching characteristics, and epitaxial growth on silicon have all been investigated in the last two decades. In this review several silicide propcrties are examined. Only transition metal silicides of the Periodic Table groups IV A, V A, VIA, and VIII are considered. Where possible, silicides are grouped accordingly. General relationships among silicides in a group and among the groups are presented. It is hoped that a better understanding of the silicides will emerge.