Line Defect/Dislocation

· Two general categories of dislocations are screw and line. Fig. 6 shows a schematic representation of a line distortion in a cubic lattice; it can be seen as an extra plane of atoms AB inserted into the lattice.

· Dislocations in a lattice are dynamic defects; that is, they can move under applied stress, dissociate into two or more dislocations, or combine with other dislocations.

· Crystals to be used in IC fabrication are generally grown free of edge dislocations, but may contain small dislocation loops from excess point defect condensation. These defects act as nuclei for the precipitation of impurities such as oxygen and are responsible for a swirl pattern seen in wafers.

· Dislocations in devices are generally undesirable, because they act as sinks for metallic impurities and alter diffusion profiles.

Fig. 6 An edge dislocation in a cubic lattice created by an extra plane of atoms. The line of the dislocation is perpendicular to the page. [2]