Compliant substrate technology: Status and prospects

Compliant substrates offer a new approach to strain management in lattice-mismatched structures. The role of the compliant substrate is to reduce the strain in a mismatched overlayer by sharing the strain via deformation of the substrate, or by nucleating and confining defects in the substrate. This can be accomplished by using a thin, “free-standing” substrate. Current efforts are primarily focused on the specification, design, and fabrication of an “ideal” compliant substrate. Key processing issues include the etching of the substrate and the bonding of the substrate to a mechanical handle wafer. Dramatically reduced dislocation densities, as well as reduced relaxation rates, have been observed for the growth of mismatched overlayers on compliant substrates.