The swirl formation of defects in Czochralski-grown silicon crystals

Abstract

Swirl defects in dislocation-free Czochralski silicon were studied by means of X-ray topography cooperated with two annealing processes. After the first annealing in N 2 for 2 h, the Pendellösung fringes of the section topographs were clearly observed as if the crystals were perfect. The second annealing in steam at 1200°C decorated the defects so as to reveal the configuration in the stage of the first annealing. When the temperature of the first annealing was sufficiently high (above ca. 800°C), some of the grown-in defects migrated and aligned along the growth layers. When the temperature was below ca. 800°C, they could not migrate so much that they remained along the crystal pulling direction as observed in as-grown crystal. The configuration of the decorated defects corresponded to the swirl pattern revealed by the Sirtl etching.