Spotty Defects in Oxidized Floating-Zoned Dislocation-Free Silicon Crystals

Spotty defect images are observed in X-ray diffraction topographs of floating-zoned dislocation-free silicon crystals subjected to thermal oxidation. The strain vector of the defects is of 1/3[111] type. The defect images in the topographs disappear when the crystals are subjected to heat treatment at 1350°C in argon atmosphere. It seems that the defect images result from the extrinsic stacking faults derived from oxygen aggregates which are formed by the interaction of the strain center appearing as a shallow etch pit and the atom of dissolved oxygen. The extrinsic stacking fault is formed by the vacancy emission from surrounding dislocation loops.