Raman study of the formation of tungsten silicide thin films

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Abstract
Raman scattering has been used to study the formation of tungsten silicide thin films. The tungsten films were sputter deposited on p-type <100≳ and <111≳ silicon substrates and the tungsten silicide formed by either rapid thermal annealing or laser annealing. Raman data were correlated with sheet resistance measurements and scanning electron micrographs to demonstrate that rapid thermal annealing at high temperatures for short times results in low resistance tungsten silicide thin films. All of the annealed samples forming tetragonal tungsten silicide display a sharp Raman peak around 333 cm−1 and a less intense peak around 450 cm−1. X-ray diffraction studies confirmed the formation of tetragonal tungsten silicide. Samples laser annealed at low laser powers show additional Raman peaks which suggest the formation of an intermediate WSix state. Finally, an estimate of the microcrystallite size of the tungsten silicide thin films was obtained from the Raman data for both rapid thermally annealed and laser annealed samples.