The migration of O2 molecules in amorphous thin films, at temperatures of between 1073 and 1273K, was studied via the thermal oxidation of Si substrates. The SiO2 films were prepared by using thermal oxidation, sputtering, chemical vapor deposition, or spin-on glass methods. It was found that the nature of the preparation method affected the diffusivities (table 118). The activation energies were estimated to be 113kJ/mol for thermally grown or sputtered films, 83kJ/mol for chemical vapor deposited films, and 59kJ/mol for spin-on films. Fourier transform infra-red spectroscopy revealed that, before and after oxidation, the Si-H bond was present in the chemical vapor deposited films. In the case of spun-on films, Si-(CH3)3 bonds were observed. The thermally grown or sputtered films consisted of a continuous random network of SiO2. In the case of the chemical vapor deposited or spun-on films, the random structure was partially terminated by Si-H and Si-(CH3)3 bonds, respectively. This increased the mean dimensions of the unit cell of the network.

M.Susa, H.Shinohara, K.Nagata, K.S.Goto: Journal of the Japan Institute of Metals, 1990, 54[2], 193-200

Table 118

Diffusivity of O2 Molecules in Silica Films