大気圧プラズマＣＶＤ法による太陽電池用アモルファスＳｉの超高速成膜

Abstract

Further investigations to improve the quality of the amorphous silicon (a-Si) films fabricated at extremely high deposition rate by atmospheric pressure plasma CVD were performed. The electrical and optical properties of the films were investigated with the measurements of photo and dark conductivity and optical absorption, and the relationship between each deposition parameter and the film properties was studied. It became clear that the optimum input power and the deposition gap existed for both of increasing the deposition rate and improving the film properties. Furthermore, the optical gap (E opt) could be controlled by the hydrogen concentration in the plasma and the substrate temperature. As a result of optimizing the deposition parameters, it became possible to improve the film quality under the ultrahigh-rate deposition condition. The maximum deposition rate of the device-quality a-Si film was 0.28μm/s. At this deposition condition, it might be possible by scanning substrate to form a-Si film of the thickness of 0.3μm on the substrate of 1m×1m area in 200 seconds, which was more than 10 times faster than the conventional plasma CVD process. E opt of the device-quality film was in the range of 1.58≤E opt≤1/68V, , which was similar to that of a-Si film fabricated by the conventional plasma CVD at low deposition rate.