Effects of substrate temperature on properties of silicon dioxide thin-film deposited by direct photochemical vapor deposition

The direct photo-CVD SiO2 thin films are deposited by using the SiH4 and O2 as the reaction gas and the low pressure Xe excited vacuum ultra-violet (VUV) as the optical source. With ellipsometry, Fourier transform infrared spectrometer (FTIR), capacitance-voltage (C-V) measurements, the properties of the thin films deposited at different substrate temperatures are studied. The result indicates that at the range of substrate temperature from 40 to 200°C, the refractive index of the deposited films is 1.40-1.46. There are no infrared absorption peaks related to the Si-H bonding and Si-OH bonding in the thin films. The substrate temperature has great influence on the properties of both the SiO2 films and the SiO2/Si interface. The fixed charge density of the SiO2-Si system is estimated from the C-V curve, the minimum value is about 1.73×1010 cm-2.