Gap states produced by oxygen precipitation in Czochralski silicon

Many attempts have been made to clarify how variations of temperature and time of heat treatments influence the shape, size, and density of oxide precipitates. There are, however, only a few reports on defect levels in the band gap generated by oxygen precipitation and the results of these experiments differ from article to article, so that there is no consensus about the gap-state energies. In this paper we report on a systematic study of the nature of gap states produced as a consequence of oxygen precipitation in Czochralski single crystal silicon wafers subjected to a three-step annealing sequence. Those steps were homogenization, nucleation, and two growth steps. The studies were carried out using deep level transient spectroscopy. It is shown that the amount of precipitated oxygen plays an important role in the gap state generation. However, the sequence of the annealing history is absolutely dominant in the subsequent determination of the electrical characteristics of material. (C) 2003 Elsevier Science Ltd. All rights reserved.