Effects of atomic hydrogen in gas phase on a-Si:H and poly-Si growth by catalytic CVD

Abstract The effects of H atoms on the hydrogenated amorphous silicon and poly-Si film-growth in catalytic CVD processes were examined. The following results were obtained: (1) The H atom concentration in the gas phase can be as high as 1014 cm−3. This density is more than one order of magnitude higher than those in conventional plasma-enhanced CVD processes. (2) When SiH4 is introduced, the H atom density decreases sharply. This decrease is mainly caused by the loss processes on chamber walls, but gas phase reactions with SiH4 to produce SiH3 are also important. SiH3 thus produced should be one of the dominant deposition precursors for Si film-growth. (3) Atomic H etches not only amorphous but also crystalline Si, including single-crystalline one. (4) The main etching product is SiH4, but Si2H6 is also produced. Si2H6 derived from previously deposited Si compounds deteriorates the film properties. However, this deterioration can be avoided by regular chamber cleaning using H atoms.