Fluorine and hydrogen effects on the growth and transport properties of microcrystalline silicon from SiF4 precursor

Structural and electrical properties of microcrystalline silicon (μc-Si:H) films grown at 200 °C from SiF4 precursor have been studied. A particular growth mechanism in which the material is completely crystallised from the initial stages of deposition is revealed by in situ ellipsometry measurements. Time resolved microwave conductivity (TRMC) measurements were performed on samples deposited at various conditions and an optimum in the total pressure and the hydrogen dilution which maximise the crystalline fraction and the transport properties was found. A mobility as high as 7 cm2/V s was measured for a 0.14 μm thick sample. The nature of the substrate (a-SiN:H and SiO2) and its deposition temperature were found to affect the composition of the μc-Si:H deposited on it.