SLOW POSITRON-ANNIHILATION SPECTROSCOPY AND ELECTRON-MICROSCOPY OF ELECTRON-BEAM EVAPORATED COBALT AND NICKEL SILICIDES

Metal silicide thin films on single-crystal silicon substrates are the subject of much research, due to their applications as electrical contacts and interconnects, diffusion barriers, low resistance gates, and field-assisted positron moderators, among others. Defects within the silicide layer and/or at the silicide/silicon interface are detrimental to device performance, since they can act as traps for charge carriers, as well as positrons. Pinholes penetrating the film are another detriment particularly for cobalt silicide films, since they allow electrons to permeate the film, rather than travel ballistically, in addition to greatly increasing surface area for recombination events. A series of epitaxial cobalt and nickel silicide thin films, deposited via electron-beam evaporation and annealed at various temperatures, have been grown on single-crystal silicon (111) substrates, in an effort to establish a relationship between deposition and processing parameters and film quality. The films have been analyzed by transmission and scanning electron microscopy, sputter depth profile Auger, and slow positron annihilation spectroscopy. The latter has been shown to both correlate and complement the traditional electron microscopy results. © 1990, American Vacuum Society. All rights reserved.