Oxygen precipitate precursors and low temperature gettering processes.: I.: Segregation of oxygen and thermal donor generation in the 600-850°C range

We report in this paper the results of a systematic investigation on the segregation of oxygen in Czochralsky silicon wafers submitted to a two-step annealing sequence, the first of which is carried out at 470 degrees C and the second at temperatures ranging from 600 to 800 degrees C. The oxygen content evolution and the segregation of oxide phases was followed using Infra Red absorption measurements at room temperature, while the generation of thermal donors was detected by electrical conductivity measurements. It was found that a close correlation exists between the old thermal donors (OTD) decomposition and the generation of new thermal donors (NTD). Furthermore, the role of preannealing time at 470 degrees C was investigated, and some interesting correlations were found between preannealing time and annealing temperature and the process of oxygen segregation as an amorphous oxide and as NTD. It was found that a temperature as low as 700 degrees C is sufficient, after a proper preannealing step, for segregating all the oxygen in solution as an amorphous oxide. Finally, we show that a model recently proposed by Pantelides for the atomic dynamics during silicon oxidation can also be used to describe oxide segregation in a silicon matrix. (C) 1999 Elsevier Science Ltd. All rights reserved.