Dislocations in Silicon Single Crystals

Dislocations and layer structures in silicon single crystals pulled by the Czockralski method are investigated by means of copper decoration as well as of etching with Dash's etchant. In the seeding process, a dislocation network is formed in the neighborhood of the interface between the seed and the grown crystal. Some of the dislocations propagate from the network into the grown crystal, their density being reduced under a favorable circumstance of crystal growth. Two types of layer structures are observed, one in dislocation free crystals and the other in crystals containing dislocation networks. These structures are ascertained to be caused by stratified accumulation of oxygen atoms in the form of clusters for dislocation free crystals and by stratified precipitation of oxygen atoms on the nodes of dislocation network for crystals containing many dislocations. Some interesting phenomena concerning the slips of the dislocations are discussed.