Rapid thermal processing induced vacancy-oxygen complexes in Czochralski-grown Si1−xGex

Abstract

Rapid thermal processing (RTP) induced vacancy-oxygen (VOm m ≥ 2) complexes can act as the precursors for oxide precipitate nucleation thus enhancing oxygen precipitation (OP) in Czochralski silicon (Cz-Si). In our preceding work, we have reported that 1020 cm−3 germanium (Ge)-doping in Cz-Si facilitates the formation of VOm complexes during the high temperature RTP. Then, how the even higher Ge-doping at 1021 cm−3 in Cz-Si affects the formation of VOm complexes during the RTP is an interesting issue to be addressed. Actually, such high Ge-doping in Cz-Si forms Cz-Si1−xGex alloys. In the present work, we have investigated the formation of VOm complexes in Cz-Si1−xGex (x = 0.035–0.038) wafers subjected to the high temperature RTP. The Cz-Si1−xGex wafers are found to exhibit much weaker OP than Cz-Si counterparts when subjected to the same two-step (nucleation-growth) anneal following the high temperature RTP, indicating that the formation of VOm complexes during the RTP is suppressed in Cz-Si1−xGex wafers. The ‘gold-marker method’ in combination with deep level spectroscopy further confirms the suppressed formation of VOm complexes in Cz-Si1−xGex wafers during the RTP. Besides, the characterization of the oxygen out-diffusion depth profiles in Cz-Si1−xGex and Cz-Si wafers annealed at different temperatures in the range 650–1000 °C indicates that the oxygen diffusivity in Cz-Si1−xGex is a little smaller. The calculations based on density functional theory reveal that in Cz-Si1−xGex the vacancies incline to locate at the first nearest neighboring sites of the Ge atoms and the capture of Oi atoms by the vacancies is less energetically favorable. The aforementioned adverse conditions are believed to be responsible for the suppressed formation of VOm complexes in Cz-Si1−xGex.