Identification of Growth Precursors In Hot Wire CVD of Amorphous Silicon Films

Abstract

ABSTRACTA soft ionization laser-based technique using 10.5 eV photon energy has been used to probe radical growth precursors in the hot wire chemical vapor deposition (HW-CVD) of a-Si:H. Using a Re filament, it is shown that Si, SiH3, and Si2H6are the major silicon-containing species formed from the hot wire dissociation of silane, and SiH2is at most a very minor product. However, chamber history is found to influence the radical species produced; i.e. SiH3 and Si2H6are largely related to the chamber wall and filament conditions. The gas species produced by W and Re filaments at wire temperatures between 1000oC and 2000oC have been studied and compared. Heating the filament to higher temperatures increases the flux of Si, SiH3 and Si2H6 in a similar fashion for both filament materials. Above 1800oC, the Si intensity saturates, while SiH3 and Si2H6show monotonic increase without saturation up to 2000oC.