In-situ stress changes of WSi/sub x/ film during polycide process sequence

In-situ stress changes of capped and uncapped sputtered tungsten silicide films were studied. In addition, film resistivity, grain size and film morphology as a function of temperature were examined. Rutherford backscattering (RBS), X-ray diffraction (XRD), and transmission electron microscopy (TEM) were used to determine film composition, morphology, and grain size. The stress characteristics were used to calculate activation energies for the phase change induced by high-temperature processing of these films. The activation energies for the transformation from the amorphous to the metastable hexagonal phase and from that to the stable tetragonal phase were determined to be 2.04 eV and 3.66 eV, respectively. The coefficient of thermal expansion was found to be identical for both the phases of tungsten silicide and was calculated to be 15.45E-6/ degrees C. The information reported in this study can be used to calculate the stress in the tungsten silicide film at every step of the polycide process sequence and to optimize the process conditions to minimize the stress in the film. The importance of the temperature of deposition of the cap oxide film is shown.<
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