CHARACTERIZATION OF SI-RICH WSIX ON SI

The structural change of CVD WSi2.6 by annealing in vacuum and in oxygen atmosphere has been studied. By annealing in vacuum, the first phenomenon, which occurs at 400°C, is crystallization of the amorphous film to a metastable semiconducting hexagonal WSi2. Excess Si in WSi2.6 has already precipitated at the WSi2/Si interface. The second phenomenon, which occurs at 600°C, is the phase transformation of the hexagonal structure to the tetragonal one. Above 1000°C, the precipitated excess Si grows epitaxially on the Si(100) substrate, while a SiO2 layer is formed by oxidizing above 700°C. The film thickness of the SiO2 layer increases with the increase of the oxidation temperature. Owing to the increment of the film thickness, the interface between WSi2 and Si moves into the Si substrate. Moreover, there are some circular parts crystallized as a tetragonal SiO2 (α-cristobalite) of about 5 μm in diameter. © 1989.