Structural and surface properties of Si1−xGex thin films obtained by reduced pressure CVD

This paper investigates the structure and surface characteristics, and electrical properties of the polycrystalline silicon-germanium (poly-Si1−xGex) alloy thin films, deposited by vertical reduced pressure CVD (RPCVD) in the temperature range between 500 and 750 °C and a total pressure of 5 or 10 Torr. The samples exhibited a very uniform good quality films formation, with smooth surface with rms roughness as low as 7 nm for all temperature range, Ge mole fraction up to 32% (at 600 °C), textures of 〈2 2 0〉 preferred orientation at lower temperatures and strong 〈1 1 1〉 at 750 °C, for both 5 and 10 Torr deposition pressures. The 31P+ and 11B+ doped poly-Si1−xGex films exhibited always lower electrical resistivity values in comparison to similar poly-Si films, regardless of the employed anneal temperature or implantat dose. The results indicated also that poly-Si1−xGex films require much lower temperature and ion implant dose than poly-Si to achieve the same film resistivity. These characteristics indicate a high quality of obtained poly-Si1−xGex films, suitable as a gate electrode material for submicron CMOS devices.