Transmission electron microscope study of ion beam induced interfacial reactions in molybdenum thin films on silicon

Abstract

Transmission electron microscopy has been applied to study molybdenum thin films on silicon. Polycrystalline molybdenum films, 500 Å in thickness and 500–1500 Å in grain size, were chemical vapor deposited on (001) oriented, n-type silicon substrate heated to 650–700°C in hydrogen ambient. The samples were then implanted with 150 keV Ar + to fluences 3×10 15-1×10 16/ cm 3 with the dose rate about 6×10 12/cm 2·s. Hexagonal MoSi 2, tetragonal MoSi 2 and hexagonal Mo 5Si 3 were found to form mainly along grain boundaries. Silicide formation along grain boundaries was also found for in-situ annealing of the thin foil at 700°C for 2 h in the electron microscope. The observations provide direct evidence of the important role of grain boundary diffusion in the formation of silicides.