Patent ID: 6093648
Filing Date: 2000-07-25
Classification: C30B,Y10S

Abstract:
A diffusion method in the production of a double-structure discrete substrate comprising a diffused layer having a thickness (Xj) on one side and a non-diffused layer having a thickness (Xi) on the other side and further having an average surface dislocation density of less than 5000 pieces/cm.sup.2 on the surface of the non-diffused layer, obtained by lapping a silicon semiconductor wafer, wherein the method comprises:forming a diffused layer on both sides of a raw material wafer wherein processing distortions remain,removing the diffused layer on one side of the wafer or slicing the wafer into two pieces, each having a diffused layer and a non-diffused layer, characterized in that the raw material wafer thickness (T in .mu.m) before the diffusion is represented by the following formula:T=2Xj+Xi+.alpha., wherein .alpha. is an adjusting factor for determining the wafer thickness before processing and is a value in the range of 45 .mu.m.ltoreq..alpha..ltoreq.930 .mu.m, andadjusting the thickness of the raw material wafer before the diffusion so as to satisfy a dislocation density required on the non-diffused layer surface when the discrete substrate is finally produced.