The formation of interstitial swirl defects in dislocation-free floating-zone silicon crystals

Abstract

Swirl defects in quenched dislocation-free floating-zone silicon crystals have been analyzed by transmission electron microscopy (TEM). The silicon crystals were quenched from the melt to prevent impurity clustering and precipitation and to minimize their effects on the swirl defect nucleation. The TEM analysis shows that the Type A swirl defects are perfect extrinsic dislocation loops elongated along 〈100〉 directions. The smaller B type swirl defects remained undetectable by TEM indicating that these defects cause very little lattice strain. From the present data it is concluded that the silicon self-interstitials are the dominant point defects during the crystal growth process. An impurity interstitial clustering mechanism is proposed for the swirl defect formation during the growth of floating zone silicon single crystals.