Patent ID: 8338269

Claim:
A method of forming a semiconductor-on-insulator (SOI) structure, comprising: subjecting an implantation surface of a donor semiconductor wafer to an ion implantation step to create a weakened slice in cross-section defining an exfoliation layer of the donor semiconductor wafer, where the donor semiconductor wafer has a width, a depth and a height, the width and depth defining X- and Y- axial directions, and the height defining a longitudinal axis; and wherein the ion implantation step includes spatially varying the implantation of ions in at least one of the X- and Y- axial directions such that ions are implanted at a maximum depth below the implantation surface one of (a) along an initial edge, (b) at an initial point, or (c) in an initial region of the weakened slice of the donor semiconductor wafer and at comparatively shallower depths below the implantation surface at successively further distances for the one of (a) the initial edge, (b) the initial point, or (c) the initial region in the at least one of the X- and Y- axial directions, such that a depth of the weakened slice below the implantation surface resulting from the ion implantation step varies spatially across the weakened slice in at least one of the X- and Y- axial directions from the maximum depth to a minimum depth; elevating the donor semiconductor wafer to a temperature sufficient to initiate separation at the weakened slice from the one of (a) the initial edge, (b) the initial point, or (c) the initial region in the at least one of the X- and Y- axial direction; and further elevating the temperature of the donor semiconductor wafer in a controlled manner to further temperatures to continue separation along the exfoliation layer in the at least one of the X- and Y- axial directions from highest density to lowest density in a controlled manner as a function of the varying depths of nucleation sites.