Patent ID: 6855620
Filing Date: 2005-02-15
Classification: H01L

Abstract:
1. A method for fabricating a Group-III nitride compound semiconductor substrate through epitaxial growth of a Group-III nitride compound semiconductor layer on a substrate base, and removal of the substrate base, said method comprising: forming an underlying layer on a substrate base, the underlying layer comprising at least one Group-III nitride compound semiconductor layer, and the uppermost layer of the underlying layer being a first Group-III nitride compound semiconductor layer; forming a first trench/mesa structure in which at least a portion of the first Group-III nitride compound semiconductor layer, at least a portion of the underlying layer and at least a portion of the surface of the substrate base are removed through etching so as to form an island-like structure, thereby providing said first trench/mesa structure including mesas formed on the underlying layer and trenches whose bottoms sink into the surface of the substrate base; performing a first lateral epitaxial growth in which a second Group-III nitride compound semiconductor layer is epitaxially grown, vertically and laterally, with top surfaces of the mesas and sidewalls of the trenches serving as nuclei for crystal growth, thereby filling upper portions of the trenches and covering the mesas; forming a second trench/mesa structure in which the entire underlying layer that has not undergone etching in the formation of the first trench/mesa structure, excepting a peripheral portion of the underlying layer, is removed by etching, a portion of the second Group-III nitride compound semiconductor layer formed on the underlying layer and at least a portion of the surface of the substrate base are also removed by etching, so as to provide said second trench/mesa structure including mesas formed on the remaining second Group-III nitride compound semiconductor layer and trenches whose bottoms sink into the surface of the substrate base; performing a second lateral epitaxial growth in which a third Group-III nitride compound semiconductor layer is epitaxially grown, vertically and laterally, with top surfaces of the mesas and sidewalls of the trenches in the second trench/mesa structure serving as nuclei for crystal growth, thereby filling upper portions of the trenches and covering the mesas in the second trench/mesa structure; and removing the substrate base and the remaining underlying layer which has not been removed in the formation of the second trench/mesa structure, to thereby produce a substrate comprising the remaining second Group-III nitride compound semiconductor layer and the third Group-III nitride compound semiconductor layer.