Patent ID: 9676670
Date: 2017-06-13
CPC Classifications: C04B,H01L,Y10T

Claim:
1. A handle substrate of a composite substrate for a semiconductor: said handle substrate consisting essentially of a translucent polycrystalline alumina sintered body comprising a sintering aid comprising at least magnesium; wherein a concentration of magnesium at a bonding face of said handle substrate to a donor substrate is half or less of an average concentration of magnesium of said handle substrate; wherein a center line average surface roughness Ra in microscopic vies of said bonding face of said handle substrate is 5 nm or smaller; wherein said alumina sintered body comprises alumina crystal grains having an average grain size of 5 to 60 μm; wherein said alumina sintered body has a relative density of 98 percent or higher; wherein magnesium is present in said alumina sintered body in a concentration of less than 300 ppm in terms of magnesium oxide; and wherein an amount of an impurity excluding alumina and magnesium oxide in said sintered body is 0.2 mass percent or smaller.