Formation of Grown-in Defects during Czochralski Silicon Crystal Growth

Abstract

The formation behavior of grown-in defects in Czochralski silicon (CZ-Si) crystals was investigated using two crystals that were quenched during growth but in one case after crystal growth had been halted for 5 h. The distributions of grown-in defect density and size, and their micro-structures were analyzed as a function of temperature during crystal growth just before quenching by means of an optical precipitate profiler (OPP) and an atomic force microscope (AFM) coupled with a laser particle counter. The formation of grown-in defects, which are considered to be octahedral voids, was found to consist of two dominant processes. The first step involves rapid void growth in a narrow temperature range of about 30° C below 1100° C and the subsequent step consists of an oxide film growth on the inner surface of the void during the cooling process to about 900° C after void formation. It was also found that the growth of the oxide film in the voids is rate-limited by the diffusion rate of oxygen atoms in silicon. In addition, it is strongly suggested that void formation in such a narrow temperature range is due to a rapid agglomeration of vacancies.