The role of prismatic dislocation loops in the generation of glide dislocations in Cz-silicon

The aim of this work is to understand the mechanisms that lead to warpage of Czochralski silicon wafers. We propose that under sufficiently large stresses, the prismatic loops which are punched-out from oxide precipitates during precipitation can initially grow as long dipoles until they cross-slip. Subsequently, dislocation multiplication can occur at the sites where cross-slip takes place, by creation of Frank–Read sources. A model describing the movement of dipoles has been developed to calculate the time needed for the source to be operative. Calculated curves are found to be in agreement with experimental results. During high temperature treatments oxygen atoms can diffuse to the core of prismatic dislocation loops and consequently hinder the dislocation motion, or completely lock them. A model has been developed to predict the amount of oxygen at the dislocation core (and then the “unlocking” stress for a loop) by taking into account the background oxygen concentration, thermal history and position of prismatic loops. It has been shown that the model is capable of simulating the experiments.