Structural Change of Oxidation-Induced Frank Sessile Dislocation Loops in Silicon

Abstract

The conversion of Frank sessile loops to perfect dislocation loops in silicon during successive thermal oxidation has been studied by X-ray topography, chemical etching and transmission electron microscopy. Frank loops generated on any one of four {111} planes during the first oxidation are changed into perfect loops in the second oxidation process in three different ways. The temperature dependence of the conversion rate seems to follow a thermal activation process, the activation energy being about 2.4 eV. The rate is accelerated by deterioration in cleanliness of wafers and oxidizing atmosphere. According to the view that the conversion is caused by the nucleation and expansion of a pair of loops of Shockley partials inside a Frank loop, the generation of the Shockley partials is presumably attributable to the localized stress around impurity precipitates at the Frank partial.