Elimination of thermal mismatch defects in epitaxially deposited films

Abstract

A concept and process is disclosed by which an epitaxially deposited film is removed from its substrate at elevated temperatures to inhibit thermal mismatch strain induced defect generation in the epitaxial layer. The process occurs by gas phase reactions of an intermediate layer purposely deposited to react with a component in the gas stream during or after epitaxial growth. While the concept of an intermediate layer has been used extensively to improve the crystal quality of the epitaxial layer this is not the purpose of this interlayer. Although this interlayer may aid in nucleation of the epitaxial layer, the objective is to separate the epitaxial material on top of the interlayer from the substrate below the interlayer at or near the growth temperature to reduce the effects of the thermal mismatch between the substrate and epitaxial layers. An application is an addition to the above invention. A thick epitaxially deposited film can now be removed from its substrate at elevated temperatures. This epitaxial layer can now be cooled without defect generation due to the difference in the thermal expansion of the substrate and epitaxy. The epitaxial layer now becomes a substrate for either further epitaxial deposition or device fabrication.