The diffusivities of O
2 molecules in amorphous SiO
2 thin films were determined over the temperature range of 1073 to 1273 K by means of the thermal oxidation of Si substrates. The SiO
2 films were synthesized on Si substrates with the four different methods, i.e., thermal oxidation, sputtering, chemical vapor deposition (CVD) and spin-on glass (SOG) methods.
The difference of the manufacturing methods changed the diffusivities and the activation energies. The diffusivity in the thermally-grown SiO
2 films was determined to be 6.4×10
−13 m
2/s at 1273 K, which was the same with that in the sputtered SiO
2 films. On the other hand, the diffusivities in the CVD- and the SOG-SiO
2 films were determined to be 9.1×10
−13 and 1.1×10
−12 m
2/s, respectively. The activation energies were calculated to be 113 kJ /mol for the thermally-grown and the sputtered films, 83 kJ /mol for the CVD films and 59 kJ/mol for the SOG films.
FT-IR (Fourier-transform infrared spectroscopy) spectra revealed the following. Both before and after the oxidation Si-H bond was observed in the CVD films. On the other hand, in the SOG films Si-(CH
3)
3 bond was observed.
The difference of the structures of the four SiO
2 films was estimated as follows. The thermally-grown and the sputtered films are consisted of the continuous random network of SiO
2. But in the CVD- and SOG-SiO
2 films the random network structure is partially terminated with Si-H and Si-(CH
3)
3 bonds, respectively, which increases the mean dimensions of the unit cell of the network.
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