Stress-induced rearrangement of oxygen atoms in Si investigated by a monoenergetic positron beam

Abstract

A monoenergetic positron beam has been used to investigate the state of interstitial oxygen in Czochralski-grown Si with coverage of SiO2 (100 nm) and poly-Si (200 nm)/SiO2 (100 nm), respectively. It was found that (i) the growth of SiO2 gives rise to a strong Doppler broadening of positrons in the bulk of Si and (ii) such a broadening can be recovered to the original level by annealing at 450 °C, by the removal of overlayers using chemical etching and by long-term aging at room temperature. This broadening was assigned to arise from the positron trapping by oxygen interstitial clusters. It was concluded that film stress is responsible for the rearrangement of oxygen atoms in Czochralski-grown Si.