Microstructural studies of epitaxial CoSi2 layers on silicon produced by ion beam synthesis and rapid thermal annealing

Abstract

Structures of cobalt disilicide layers fabricated by ion beam synthesis on (001) silicon wafers have been studied by cross-sectional transmission electron microscopy. Implantation at 350 °C with doses of 5 and 7×1017 cm−2 of 200 keV Co+ ions was used, followed by rapid thermal annealing. For the as-implanted wafer with the lower dose, a CoSi2 layer in a parallel (A-type) epitaxial orientation was formed, and below this there were CoSi2 precipitates, some in twinned (B-type) orientations, and {113} defects. With the higher dose, polycrystalline CoSi was also present at the surface and there was substantial surface roughening. For the annealed wafers, as the annealing temperature increased from 700 to 1100 °C, the CoSi2 layer progressively increased in thickness, and the CoSi at the surface of the CoSi2 layer was eliminated. In the silicon beneath the silicide layer, the CoSi2 precipitates were greatly reduced in number and the {113} defects were eliminated.