Characterization of silicide formation of LPCVD-W by means of Rutherford backscattering spectrometry and x-ray diffractometry

This paper reports tungsten disilicide (WSi2) formed by annealing 185 nm and 750 nm thick LPCVD-W films deposited on left-angle 100 right-angle-Si substrates. The thickness of the formed WSi2 was observed by Rutherford backscattering measurements (RBS) to increase parabolically with the annealing time. This agrees with the behavior reported in the literature for sputter deposited or evaporated W films. However, a higher silicide growth rate was found in this work. An activation energy of 2.6 eV/atom was measured, which is smaller than those for sputter deposited or evaporated W films. The crystal structures of the formed WSi2 and the unreacted W films were analyzed using X-ray diffraction (XRD) technique. The thermal history of the samples was found to play an important role for the crystal structure of the unreacted W and formed WSi2. The as-deposited W films became more oriented to the left-angle 100 right-angle direction with increasing film thickness, while the unreacted W films on top of the formed WSi2, from the samples annealed at temperatures from 700 to 800 degrees C, became more left-angle 100 right-angle direction dominated with decreasing W film thickness