Composite semiconductor substrate and a fabrication process thereof

Claim 1

A method for fabricating as semiconductor-on-insulator structure that includes a single crystal layer of a group III-V first compound semiconductor material formed on a single crystal substrate of sapphire, said method comprising the steps of: growing a plurality of epitaxial layers consecutively on a second substrate of a second compound semiconductor material to form a layered structure, wherein said single crystal layer is formed at one end of said layered structure and has an exposed first principal surface, said layered structure comprising an etching stopping layer such that said etching stopping layer has an etching rate different from those of the other ones of said plurality of epitaxial layers; contacting the single crystal layer to the single crystal substrate of sapphire such that the first principal surface of said single crystal layer establishes an intimate contact with a second principal surface of said single crystal substrate; bonding said single crystal layer and said single crystal substrate with each other at said mutually contacting first and second principal surfaces by elevating a temperature of said single crystal layer and said single crystal substrate such that a rearrangement of atoms occurs in said single crystal layer and in said single crystal substrate at least in correspondence to said mutually contacting first and second principal surfaces; removing said second substrate and at least one of said plurality of epitaxial layers formed between said second substrate and said etching stopping layer by a first etching process; and removing said etching stopping layer by a second etching process.

Claim 2

A method for fabricating as semiconductor-on-insulator structure that includes a single crystal layer of a group III-V first compound semiconductor material formed on a single crystal substrate of sapphire, said method comprising the steps of: growing a plurality of epitaxial layers consecutively on a second substrate of a second compound semiconductor material to form a layered structure, wherein said single crystal layer is formed at one end of said layered structure and has an exposed first principal surface, said layered structure comprising an etching stopping layer such that said etching stopping layer has an etching rate different from those of the other ones of said plurality of epitaxial layers; contacting the single crystal layer to the single crystal substrate of sapphire such that the first principal surface of said single crystal layer establishes an intimate contact with a second principal surface of said single crystal substrate; bonding said single crystal layer and said single crystal substrate with each other at said mutually contacting first and second principal surfaces by elevating a temperature of said single crystal layer and said single crystal substrate such that a rearrangement of atoms occurs in said single crystal layer and in said single crystal substrate at least in correspondence to said mutually contacting first and second principal surfaces; removing said second substrate and at least one of said plurality of epitaxial layers formed between said second substrate and said etching stopping layer by a first etching process; and removing said etching stopping layer by a second etching process.