Effects of Film Quality of Hydrogenated Amorphous Silicon Grown by Thermal Chemical-Vapor-Depositon on Subsequent in-situHydrogenation Processes

In-situhydrogenation which is performed in a thermal chemical-vapor-deposition (CVD) chamber by interrupting film growth and by introducing atomic hydrogen is known to be effective for decreasing the defect density in thermal CVD hydrogenated amorphous silicon (a-Si:H). In this study we have experimentally examined the validity of a previous implicit assumption that the film properties after in-situhydrogenation process could be insensitive to the quality of starting CVD films. This assumption has been proved to be invalid and it has been clarified that one must start with high quality CVD samples in order to obtain high quality samples after in-situhydrogenation. We explain the present results by assuming that the film structure of the thermal CVD a-Si:H, which affects the hydrogen penetration into the lattice during hydrogen plasma treatment and consequently the defect passivation, can vary with CVD growth conditions.