Prevention of oxygen incorporation in poly-Si1-xGex deposition with interfacial amorphous silicon layer

Abstract

Polycrystalline silicon germanium (poly-Si1-xGex) thin films have been deposited on thermal oxide and a-Si surfaces by rapid thermal chemical vapor deposition (RTCVD) from SiH4-GeH4-H-2. The effect of oxygen incorporation on the initial surface of poly-Si1-xGex/SiO2 has been investigated. Poly-Si1-xGex films deposited on the substrate with an amorphous silicon buffer layer on the oxide (poly-Si1-xGex/a-Si/SiO2) show better crystallinity and contain less oxygen than those deposited directly on the oxide surface (poly-Si1-xGex/SiO2). Poly-Si1-xGex films deposited directly on the oxide contain 5-23.5 at% oxygen due to the etching effect on the SiO2 surface by decomposed GeHx during the initial stages of the deposition. All films have mixed amorphous and crystalline phases and the grain size and crystallinity increased when the films were deposited on a thin a-Si layer.