The Electrical Characterization of Heteroepitaxial Semiconducting Films

Abstract

Heteroepitaxial semiconducting films (HSF) have become of considerable practical interest in the last few years, primarily because of their use in integrated circuits. Several U.S. and foreign semiconductor companies are offering products based on silicon-on-sapphire (SOS) technology. This particular combination of semiconductor and insulator has emerged as dominant mainly because silicon has the most desirable overall properties compatible with integrated circuit processing and because of all the possibly suitable insulating substrates, sapphire offers the best resistance to shattering during processing and has the lowest cost. SOS technology offers small parasitic device and interconnection capacitance and provides nearly ideal electrical isolation between devices when islands of silicon are used. Because silicon islands are involved, it is necessary to cover the steps (island edges) with different dielectrics or metals to form the circuits. This step-coverage problem is minimized by using as thin a silicon film as is practical. On the other hand, thinner films can have inferior electrical performance and may be undesirable. Typically the film thicknesses range from 0.2 to 4.0 µm, with most circuits using 0.4- to 1.0-µm films.