Naseka V. Structural-phase transformation in solar-grade silicon and silicon-oxide films

This thesis is concerned to investigation of the influence of different regimes of thermal treatment on the recombination characteristics of low-grade crystalline silicon under gettering and passivation coatings aimed to its transformation on the solar-grade material. In the thesis, the theoretical model for gettering of recombination-active Fe impurity, taking into account its precipitates present, was developed. The theoretical results for Fe atoms gettering using aluminum layer of different thickness were obtained. To improve the the efficiency of the developed model the experiments with Fe impurity implantation as well as the corresponding gettering thermal treatments were carried out. The enhanced model of Fe distribution in the crystalline silicon wafer was developed basing on the theoretical calculations and mas-spectroscopy as well as X-ray diffractometry data. It was found, that for the silicon samples grown by Czochralski method, the Fe concentration exceeds the solubility limit, which indicates that Fe atoms are in the complexes. Therefore, Fe gettering kinetic can not be described by simple interstitial diffusion. Also, in this case it is important to take into account the release/trapping by complexes (FeSi2 precipitates). Also, the thesis includes the information regarding the passivation of the surface of crystalline silicon by the non-stoichiometric oxynitride films prepared by the PECVD method from the SiH4 and N2O precursors. The kinetic of the hydrogen effusion (release) from SiOxNy films caused by isothermal treatments was investigated using IR-spectroscopy.