DISORDER IN VITREOUS SIO2 - THE EFFECT OF THERMAL ANNEALING ON STRUCTURAL-PROPERTIES

SiO2-passivation layers formed by thermal oxidation and various chemical vapor deposition (CVD) processes have been investigated by infrared spectroscopy and wet chemical etching studies in ammonium hydroxide water solutions. In order to obtain effects of thermal annealing on the dislocation structure of deposited oxides, these layers have been subjected to an annealing step. Disorder and water-related features in infrared spectra, as compared to activation energies and etch rates received from the etching experiments, show mainly two effects: the annealing of deposited films is accompanied by bond strain relaxation through viscous flow and decreased porosity without a measurable decrease in thickness. Within the infrared study, further evidence was obtained for disorder-induced mechanical mode coupling in oxides with a dislocation structure. In addition, the infrared spectroscopic and etching results for thermally grown oxides are very similar to those for annealed CVD oxides. Such a similarity was also obtained for unmodified CVD oxides processed at two very different temperatures.