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

This work deals with the structural properties of microcrystalline silicon (mu c-Si:H) films grown at low temperatures (90-220 degrees C) with high rates in atmospheric-pressure He/H(2)/SiH(4) 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 mu c-Si:H films are studied in detail as functions of film thickness and substrate temperature (T(sub)). The results show that the mu c-Si:H film deposited with 50 (SCCM) (SCCM denotes standard cubic centimeters per minute at STP) SiH(4) 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 T(sub) dependence of Raman crystallinity of the mu c-Si:H films indicates that a highly crystallized mu c-Si:H film grows even when T(sub) is reduced to 90 degrees C. Further systematic studies are needed for both device applications and deposition on thermally sensitive plastic materials.