STRUCTURE AND PROPERTIES OF RAPID THERMAL CHEMICAL-VAPOR-DEPOSITED POLYCRYSTALLINE SILICON-GERMANIUM FILMS ON SIO2 USING SI2H6, GEH4, AND B2H6 GASES

Deposition of undoped and in situ boron-doped polycrystalline silicon- germanium (poly-Si1-xGex) films on oxide has been investigated at temp eratures below 625 degrees C and a pressure of 4 Torr in a rapid therm al chemical vapor deposition system. The influences of reactant gases such as Si2H6, SiH4, GeH4, and B2H6 on the nucleation behavior, and st ructural properties of poly-Si1-xGex films formed on oxide were studie d. The experimental results showed that in situ boron-doped or undoped poly-Si1-xGex films can be directly deposited on oxide without an ini tial Si predeposition layer to provide the necessary nucleation sites on the surface when using Si2H6 as the Si source gas. However, when Si H4 was used as the Si source gas, only in situ boron-doped films can b e deposited nonselectively on the oxide without the initial Si predepo sition layer, and to deposit undoped poly-Si1-xGex films, Si predeposi tion is needed, otherwise Si1-xGex islands are formed on the oxide. X- ray diffraction analysis showed that poly-Si1-xGex films deposited usi ng Si2H6, GeH4, and B2H6 gas mixture have three singular peaks corresp onding to {311}, {220}, and {111} planes, thus indicating the Si1-xGex alloy is formed. In addition, we found that B2H6 gas has a minor effe ct on the Ge incorporation into the films but reduces the overall depo sition rate. (C) 1998 American Institute of Physics.