POLYCRYSTALLINE SILICON-GERMANIUM FILMS ON OXIDE USING PLASMA-ENHANCED VERY-LOW-PRESSURE CHEMICAL-VAPOR-DEPOSITION

Si1-xGex thin films on oxide-coated Si substrates have been formed by plasma-enhanced very-low-pressure chemical vapor deposition. Two modes of deposition, thermal and plasma enhanced, were studied using SiH4 and GeH4 at temperatures ≤600°C. In both cases, growth rates and grain sizes increase with Ge content, and the polycrystalline-to-amorphous transition temperature is lower for Si1-xGex than Si. Compared to thermal growth of polycrystalline Si1-xGex, plasma-enhanced deposition of poly-Si1-xGex promotes higher growth rates, smaller grain sizes, and direct deposition onto oxide, as well as improved structural properties such as a smoother surface and a more columnar grain texture. Plasma deposition of amorphous-Si1-xGex films followed by a crystallization anneal at 600°C results in an even smoother surface morphology with grain sizes enhanced by an order of magnitude compared to plasma-deposited poly-Si1-xGex films.© 1995 American Institute of Physics.