SILICON NUCLEATION AND FILM EVOLUTION ON SILICON DIOXIDE USING DISILANE - RAPID THERMAL CHEMICAL-VAPOR-DEPOSITION OF VERY SMOOTH SILICON ATHIGH DEPOSITION RATES

An investigation of Si2H6 and H-2 for rapid thermal chemical vapor dep osition (RTCVD) of silicon on SiO2 has been performed at temperatures ranging from 590 to 900 degrees C and pressures ranging from 0.1 to 1. 5 Torr. Deposition at 590 degrees C yields amorphous silicon films wit h the corresponding ultramooth surface with a deposition rate of 68 nm /min. Cross-sectional transmission electron microscopy of a sample dep osited at 625 degrees C and 1 Torr reveals a bilayer structure which i s amorphous at the growth surface and crystallized at the oxide interf ace. Higher temperatures yield polycrystalline films where the surface roughness depends strongly on both deposition pressure and temperatur e. Silane-based amorphous silicon deposition in conventional systems y ields the expected ultrasmooth surfaces, but at greatly reduced deposi tion rates unsuitable for single-wafer processing. However, disilane, over the process window considered here, yields growth rates high enou gh to be appropriate for single-wafer manufacturing, thus providing a viable means for deposition of very smooth silicon films on SiO2 in a single-wafer environment.