Rapid Estimation of Removal Rate of Chemical Mechanical Polishing of Gallium Nitride Substrate by Quantitative Diagnosis of Cathodoluminescence Images

Abstract

Rapid estimation of the removal rate of the chemical mechanical polishing (CMP) process of a gallium nitride (GaN) substrate contributes to the quick diagnosis of CMP progressing, leading to accelerated process development. The present study discusses the feasibility of using cathodoluminescence (CL) imaging for a rapid diagnosis of the removal rate of the CMP process. Mechanically induced subsurface damage was detected as black lines in the CL images due to nonradiative recombination. To quantitatively understand the CL images from the GaN substrate, the CL images was analyzed for the mean image brightness. We developed an advanced theory interpreting CL image brightness as a logistical function with the CMP processing time by assuming that the mechanically induced damages at and near the surface exponentially decrease with depth from the surface. Therefore, the CMP progress was successfully characterized by analyzing CL images in CMP process with the logistic functions, which provided a rapid estimation of the CMP removal rate.