Polycrystalline Si1-xGex thin film deposition by rapid thermal chemical vapor deposition

Abstract

Polycrystalline silicon germanium (poly-Si1−xGe x ) thin films on a-Si film have been deposited by rapid thermal chemical vapor deposition (RTCVD) with SiH4–GeH4–H2. Effect of GeH4/SiH4 and deposition temperature on stoichiometry (x), Si-Ge binding character, composition, hydrogen configuration, crystallinity, preferred orientation, grain size, and surface roughness of poly-Si1−xGe x films has been investigated. Poly-Si1−xGe x deposited on the substrate with amorphous silicon buffer layer on oxide shows better crystallinity and contains the less amount of oxygen than the one deposited directly on the oxide surface. At low temperature region, the Ge–H bond with the small amount of Si–H2 bond is dominant but all hydrogen bonds are desorbed at high temperature. All films have polycrystalline phase and the grain size and (111) orientation increased with increasing deposition temperature in which Ge content also increases at the fixed gas flow rate of GeH4 to total source gas. Poly-Si1−xGe x /Si thin film transistors (TFT) are fabricated and hydrogen during post-hydrogenation process preferentially is attached to Ge dangling bond and the TFT characteristics could be improved.