Effect of microstructural and interface modifications on electrical properties of molybdenum silicide thin films formed by rapid thermal annealing

The microstructural and interface modifications associated with the formation of the most stable molybdenum silicide phase from as-deposited thin films of composition Mo25Si75, Mo30Si70, Mo36Si64 and Mo42Si58 and their effects on electrical properties were studied. The interface modifications formed upon silicidation between silicide and silicon substrate were observed to depend on the silicon content in the starting composition. Large interface depths of the order of 150-600 Angstrom were observed in the silicide-silicon thin films. The changes in the interface and microstructure were observed to be due to the out-diffusion of the excess silicon available after the formation of the most stable silicide phase towards the interface at higher annealing temperatures and its distribution within the matrix of the silicide thin film at lower annealing temperatures. The effects of these microstructural modifications were clearly reflected in the electrical properties of the silicide thin films such as sudden drop in resistivity, large ideality factor of Schottky diodes and significant change in Schottky barrier heights.