Patent ID: 9673282
Date: 2017-06-06
CPC Classifications: C04B,C30B,H01L,Y10T

Claim:
1. A composite substrate for a semiconductor: said composite substrate comprising a handle substrate and a donor substrate, said handle substrate comprising polycrystalline alumina; wherein said handle substrate comprises an outer peripheral edge part and a central part, wherein said outer peripheral edge part has an average grain size of 20 to 55 μm; and wherein said central part has an average grain size of 10 to 50 μm; wherein said average grain size of said outer peripheral edge part of said handle substrate is 1.1 times or more and 3.0 times or less of said average grain size of said central part of said handle substrate, and wherein said handle substrate further comprises a single bonding face comprising a central face part on said central part and an outer peripheral edge face part on said outer peripheral edge part, and wherein said central face part and said outer peripheral edge face part of said bonding face of said handle substrate are bonded to said donor substrate.