PREVENTION OF OXYGEN INCORPORATION IN POLY-SI1-XGEX DEPOSITION WITH INTERFACIAL AMORPHOUS-SILICON LAYER

Polycrystalline silicon germanium (poly-Si1-xGex) thin films have been deposited on thermal oxide and a-Si surfaces by rapid thermal chemica l vapor deposition (RTCVD) from SiH4-GeH4-H-2. The effect of oxygen in corporation on the initial surface of poly-Si1-xGex/SiO2 has been inve stigated. Poly-Si1-xGex films deposited on the substrate with an amorp hous silicon buffer layer on the oxide (poly-Si1-xGex/a-Si/SiO2) show better crystallinity and contain less oxygen than those deposited dire ctly on the oxide surface (poly-Si1-xGex/SiO2). Poly-Si1-xGex films de posited directly on the oxide contain 5-23.5 at% oxygen due to the etc hing effect on the SiO2 surface by decomposed GeHx during the initial stages of the deposition. All films have mixed amorphous and crystalli ne phases and the grain size and crystallinity increased when the film s were deposited on a thin a-Si layer.