Microcrystalline Si films grown at low temperatures (90–220 °C) with high rates in atmospheric-pressure VHF plasma

Abstract

This work deals with the structural properties of microcrystalline silicon (μc-Si:H) films grown at low temperatures (90–220 °C) with high rates in atmospheric-pressure He/H2/SiH4 plasma, which is excited by a 150 MHz very high frequency power using a porous carbon electrode. This plasma permits to enhance the chemical reactions both in gas phase and on the film-growing surface, while suppressing ion impingement upon the surface. Raman crystalline volume fractions of the μc-Si:H films are studied in detail as functions of film thickness and substrate temperature (Tsub). The results show that the μc-Si:H film deposited with 50 (SCCM) (SCCM denotes standard cubic centimeters per minute at STP) SiH4 has no amorphous transition layers at the film/substrate interface in spite of the high deposition rate of 6.4 nm/s, which is verified by the cross sectional observations with a transmission electron microscope. In addition, the Tsub dependence of Raman crystallinity of the μc-Si:H films indicates that a highly crystallized μc-Si:H film grows even when Tsub is reduced to 90 °C. Further systematic studies are needed for both device applications and deposition on thermally sensitive plastic materials.