OBSERVATIONS OF SWIRL DEFECTS IN AS-GROWN DISLOCATION-FREE CZ SILICON CRYSTALS.

The swirl defects in as-grown dislocation-free CZ silicon crystals have been studied through preferentially chemical etching, infrared absorption spectrum and transmission electron microscopy. It is proved that two types of swirl defects can be observed in unannealed as-grown silicon. The type I swirl defects are dislocation loops, clusters of dislocation loops and stacking faults, and the type II defects are precipitates. After extensive TEM observations combined with IR absorption spectrum analysis, it is believed that these precipitates are alpha -cristobalite plate (SiO//2). Another kind of microdefect, type III, with dimension less than 100 A and with densities of 10**1**3-10**1**4 cm** minus **3, has been observed in some specimens.