Reduction of dislocation density in Si by thermal cyclic annealing

The thermal cyclic annealing technique is applied to Si single crystals. X-ray topography is used to determine the nature of the individual dislocations. Comparison of the dislocation structures before and after the thermal cyclic annealing reveals that the degree of crystal perfection is improved substantially by the thermal cyclic annealing. The density of the pure screw and 60° dislocations decreases very rapidly, while that of Lomer dislocations remains practically unchanged during the annealing. Thus, it is concluded that the effectiveness of the thermal cyclic annealing in improving the degree of crystal perfection is limited by the occurrence of Lomer dislocations.