Thickness dependence of properties of plasma-deposited amorphous SiO2 films

Amorphous SiO2 (a-SiO2) films were deposited at 300 degreesC by plasma-enha nced chemical vapor deposition using SiH4-O2 Mixtures. The [O-2]/[SiH4] rat io was maintained at 1.5, in which oxide films having a stoichiometric comp osition could be obtained. The Si-O-Si stretching mode, stress, the density of Si dangling bonds and buffered HF (BHF) etch rate were investigated as a function of film thickness. It was found that the peak frequency of Si-O- Si stretching mode centered at around 1050 cm(-1) increased from 1050 to 10 75 cm(-1) with increasing film thickness front 0.1 to 1.1 mum. By compariso n with calculations based on the effect of multiple reflections in film/sub strate system, it was found that the shift of the Si-O-Si stretching mode t o high frequencies was due not only to the effect of multiple reflections, but also to the physical effect of thermal heating and/or ion bombardment d uring film growth, which would contribute to rearrangement of the Si-O-Si b onding network. The experimental results for the stress behavior, the densi ty of Si dangling bonds and BHF etch rate confirmed this finding.