Cyclic thermal anneal for dislocation reduction

摘要

The invention provides processes for producing a very low dislocation density in heterogeneous epitaxial layers with a wide range of thicknesses, including a thickness compatible with conventional silicon CMOS processing. In a process for reducing dislocation density in a semiconductor material formed as an epitaxial layer upon a dissimilar substrate material, the epitaxial layer and the substrate are heated at a heating temperature that is less than about a characteristic temperature of melting of the epitaxial layer but greater than about a temperature above which the epitaxial layer is characterized by plasticity, for a first time duration. Then the epitaxial layer and the substrate are cooled at a cooling temperature that is lower than the about the heating temperature, for a second time duration. These heating and cooling steps are carried out a selected number of cycles to reduce the dislocation density of the epitaxial layer.