Crystallographic control of microcrystalline silicon films in a SiF/sub 4//SiH/sub 4//H/sub 2/ plasma by VHF-PECVD

摘要

The effects upon the crystallographic properties of silicon films prepared from SiF/sub 4//SiH/sub 4//H/sub 2/ gas mixtures by varying the flow rate of SiF/sub 4/, input power, and the distance between parallel plate electrodes of capacitively coupled very high frequency plasma enhanced (VHF-PECVD) reactor are systematically studied. The results show that at low powers an appropriate electrode distance for best crystallinity is about 15 mm. The appropriate power for best crystallinity with a highest Bragg reflection peak of Si (220) is about 60 W. The SiF/sub 4/ addition suppresses the formation of crystallographic texture (111). Noticeably, the addition of SiF/sub 4/ significantly effects upon (311) oriented texture as the peak-intensity ratio of (311)/(111) is directly proportional to SiF/sub 4/ flow rate. Increasingly added SiF/sub 4/ causes the increased internal strain, grain size, and crystallinity evidenced by the results of apparent grain sizes and the D-spacing.