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 10 14 cm −3. This density is more than one order of magnitude higher than those in conventional plasma-enhanced CVD processes. (2) When SiH 4 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 SiH 4 to produce SiH 3 are also important. SiH 3 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 SiH 4, but Si 2H 6 is also produced. Si 2H 6 derived from previously deposited Si compounds deteriorates the film properties. However, this deterioration can be avoided by regular chamber cleaning using H atoms.