Ultraviolet bleaching and regeneration of ⋅Si≡Si3 centers at the Si/SiO2 interface of thinly oxidized silicon wafers

The ⋅Si≡Si3 defect revealed by electron spin resonance (ESR) at the Si/SiO2 interface has been found to be very sensitive to ultraviolet (UV) radiation at 2537 A. With native oxides or very thin thermal oxides, UV bleached the signal, which then recovered slowly in room temperature air, or rapidly upon water immersion. Details of the bleaching suggest outer-oxide surface trapping by adsorbed oxygen, rather than bulk oxide traps. In HF-stripped silicon, an opposite uv effect was observed, i.e., an accelerated growth of ⋅Si≡Si3 centers. The physico-chemical responses of ⋅Si≡Si3 reflected several stages in the development of nascent oxides on silicon wafers. The uv trapping phenomenon further offers a potential method for determination of the energy levels of the ⋅Si≡Si3 defect, and thus for clarification of its role in interface trapping.