Linear dependence of dislocation pattern size on the imprint width and scratch width on (0001) GaN

Abstract

With the aim of developing a method of estimating the thickness of an affected layer on a wide-bandgap semiconductor wafer caused by scratching, we investigated the dependence of dislocation pattern size on the width of the imprint (or scratch) induced by the Berkovich indentation (or scratching) using a Berkovich indenter. We found that the penetration depth and width of the dislocation pattern induced on (0001) GaN by indentation are approx. 0.9 times and 30 times that of the imprint width and the imprint depth, respectively. Based on the linearity between the imprint width and the square root of load (SqL), the constant hardness is confirmed to be 0.1 mN or more. In comparison to laterally expanding dislocation generation, inclined dislocation generation has a lower threshold load. The cause of this threshold discrepancy is discussed based on the imperfection of the indenter tip. The scratch width linearly increased with the SqL in the range of 0.5–7 mN. The width and depth of the dislocation pattern induced by the scratch are approx. 11–13 and 0.75–1 times the scratch width, respectively. The width of the dislocation pattern of the [100] scratch is larger than that of the [110] scratch, however, the penetration depth of the dislocation pattern of [100] is smaller than that of [110]. These findings indicate that estimating the affected layer thickness induced by mechanical polishing or grinding is possible only by finding the widest scratch on a wafer.