Y. Maemura, T. Takagi*, R.Hayashi*, W. Futako*, M.Kondo*, A. Matsuda* and H. Fujiyama

Faculty of Engineering Nagasaki University 1-14 Bunkyo, Nagasaki 852-8521, Japan
*Electrotechnical Laboratory 1-1-4 Umezono, Tsukuba-shi, Ibaraki 305-8568,Japan
hazuki@ec.nagasaki-u.ac.jp

Hydrogenated amorphous silicon (a-Si:H) grown from silane (SiH4) plasma is an important material for their applications to large area,thin film devices, and it is necessary to increase the production throughput. However the powder formation due to the gas phase polymerization occurs under the high growth rate conditions of a-Si:H, which results in an overall reduction of the production throughput and a deterioration of optoelectronic properties of resulting films.

In this work, we investigated the effects of electrode distance as an important external control parameter in the SiH4 plasma for the preparation of a-Si:H in the rf plasma enhanced chemical vapor deposition (PECVD) with capacitively coupled parallel plate electrodes. The deposition rate of a-Si:H film increased with the shortening of the electrode distance. This is regarded as the result of an increase in electron temperature due to the plasma self-organization mechanism. Furthermore, shortening the distance betweent he cathode (not heated) and heated anode results in a drastic suppression of powder formation near the cathode as an influence of heated anode. Namely, when the electrode distance is reduced, SiH4 density is decreased in a discharge space near the cathode by the heat from the anode, leading to a reduction of higher silane generation rate inthe relevant space. We have also observed the optoelectronic properties of resulting films through the effects of electrode distance and substrate temperature.