The locking of dislocations by O atoms in Czochralski material was investigated experimentally and theoretically. Experiments were performed at temperatures of between 700 and 850C, using various annealing times and O concentrations. These revealed 5 distinct regimes for the unlocking stress as a function of annealing time. The unlocking stress first increased almost linearly with time, and then saturated. The saturation stress, the time required to reach saturation and the duration of saturation depended upon the annealing conditions and O content. Following saturation, a rapid increase and a second saturation of the unlocking stress were observed with increasing annealing time. The locking effect was greatly reduced after long annealing times. The interaction energy between an O atom and a dislocation was deduced from the temperature dependence of the first saturation stress, and it was shown that the change in entropy which occurred when an O atom was trapped at a dislocation was significant. The transport of O to dislocations was also investigated by solving the diffusion equation numerically. Both the trapping and emission of O atoms from the dislocation core were considered in the calculations.

On the Locking of Dislocations by Oxygen in Silicon. S.Senkader, K.Jurkschat, D.Gambaro, R.J.Falster, P.R.Wilshaw: Philosophical Magazine A, 2001, 81[3], 759-75