Extremely High-Rate Deposition of High-Quality Amorphous Silicon Carbide Films

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Using the atmospheric pressure plasma chemical vapor deposition (CVD) technique, hydrogenated amorphous Si_<1-x>C_x(a-Si_<1-x>C_x : H) films deposited at extremely high rates. The films were prepared on Si(001) wafers at atmospheric pressure in a very high frequency (VHF) plasma of gas mixtures containing He, H_2, SiH_4 and CH_4. First, deposition rate and film properties (structure, density and composition) were studied by transmission electron microscope (TEM), Auger electron spectroscopy (AES) and infrared (IR) absorption spectroscopy as a function of CH_4 concentration. It was found that the maximum deposition rate was 5Onm/s, which was more than 10 times faster than that achieved by the conventional plasma CVD technique, although the deposited films had sparse atomic structures. In order to improve the structure of the a-Si_<1-x>C_x : H films, further investigations were performed. Structure (C-H and Si-H bond densities) and composition of the a-Si_<1-x>C_x:H films were studied as functions of VHF power, CH_4/SiH_4 ratio and the substrate temperature by IR absorption spectroscopy and AES. Surface morphology of the films was observed by scanning electron microscope (SEM). It was implied that particles generated in gas phase deteriorated the film morphology and caused excessive incorporation of hydrogen atoms in the film. Both suppressing particle formation in gas phase and elimination of excessive hydrogen atoms bonded to C and Si atoms at the film-growing surface were important factors to enhance Si-C network formation. As.a result of optimising the deposition parameters, a stoichiometric a-SiC:H film could be deposited at the substrate temperature of 550℃.