TRANSITION-METAL SILICIDES IN SILICON TECHNOLOGY

Studies of the properties and characteristics of transition metal silicides have been stimulated by their (potential) use in integrated circuit technology. This review describes some of the most recent studies in this field of research. Formation mechanisms of silicides are discussed in some detail. A division is made between near-noble and refractory metal silicidation which aids in the understanding of differences in formation mechanisms of the various silicides. The evolution of the components of thin film stress during metal silicidation is also elucidated. In the review of the practical uses of these materials, emphasis is placed on specific processes involving laterally confined (self-aligned) silicide film formation as more advanced applications require film formation only in certain localized regions on a Si wafer. Specific attention is paid to the silicidation processes of TiSi2 and CoSi2. The electronic structure of silicides is discussed on the basis of band-structure calculations and photoemission experiments. The important electrical characteristics of films are then examined in terms of the microstructure of the films. A review of the crystallographic (epitaxial) orientation relationships between silicide films and monocrystalline Si is given. The epitaxial growth of CoSi2 and FeSi2 on and in Si is discussed thoroughly. The review of epitaxial silicide formation is used as the basis for a description of some futuristic applications of these materials. One such application utilizes the semiconducting properties of a FeSi2 phase while another employs the Schottky-barrier characteristics of silicide/Si interfaces for the formation of advanced transistors. The latest electrical results obtained from the semiconducting material and from a so-called permeable base transistor are presented.