Phase Transformation and Microstructural Properties in Sputtered Vs. CVD WSi, Films

CVD WSi, films produced by dichlorosilane reduction at 570°C and WSi, films sputter deposited at 50°C were characterized by in situ x-ray diffraction (IS-XRD), in situ resistivity (ISRes), in situ stress (IS-stress), ex situ/in situ transmission electron microscopy (EX/IS-TEM) and ex situ Auger electron spectrometry (EX-AES) over the temperature range 25–1100°C. The CVD films were crystalline after deposition, with columnar grains in the hexagonal phase and a Si:W atomic ratio of 2.6:1. The CVD films exhibited a sharp hexagonal to tetragonal phase transformation near 750°C. The final grain size was greater than the film thickness, with no evidence of voiding. Avrami analyses gave traditional curves with n values of 2 for the phase transition in the CVD films. In comparison, the sputtered films were amorphous as deposited (Si:W atomic ratio of 2.8:1 ) and crystallized to a different hexagonal phase microstructure than did the CVD films. The sputtered films showed a broad hexagonal to tetragonal phase transformation near 800°C, and a final grain size that was less than the fihn thickness with much voiding. A low Avrami exponent of 0.2 to 0.4 was obtained for the transformation of the sputtered films.