It is known that internal mechanical stresses (IMS) due to the differences in the thermal expansion coefficients between films and substrates and lattice mismatch appear in the Si-SiO2 system during the process of its formation and that point defects (PD) generation and redistribution could be used to reduce partially the surface strains. However, this process on the atomic scale is till not studied. The goal of the present report is to investigate the strain relaxation mechanism in the Si-SiO2 system and its modification by laser irradiation using EPR, IR absorption spectroscopy, scanning elektron microscopy (SEM) and samples bending measurements. PD density and stresses in the Si-SiO2 system were varied by oxidation condition (temperature, time, cooling rate, ambient) and by Si3N4 deposition on SiO2. Different sign of the thermal expansion coefficient of the SiO2 and Si3N4 on Si allow to modifay the IMS at the interface. It has been found that samples bending decreases or increases simultaneously with EPR signal intensity depending on the oxidation condition (temperature). At lower temperature (11000C) the bending of the samples decreases with the increase of the EPR signal intensity (vacancies) while at a higher oxidation temperature (12000C) the bending and EPR signal increase simultaneously. These allows to suggest that at lower oxidation temperature PD reduce the IMS, while at higher oxidation temperature IMS created PD. It has been shown that after laser irradiation the samples bending decrease or increase depending on the laser irradiation intensity.A possible reason for that can be the change of the IMS under laser irradiation and compressive or tensil stresses formation at the interface.
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