4H-SiC Full Wafer Mapping Image of CMP-Finished Sub-Surface Damage by Laser Light Scattering

Abstract

Developing an observation method for distributing sub-surface damage (SSD) on large-diameter 4H-SiC bulk wafers formed by mechanical processing can significantly improve the epitaxial and bulk growth processes. This study used a novel laser light scattering (LLS) technique to observe SSD distribution on a 6-inch 4H-SiC (0001) wafer. As a result, scattering intensity distributions similar to the grinding and lap-polishing traces and the shape of the jig used to hold the wafer during polishing were observed on the CMP-finished SiC wafer surface. Since the surface topography of the area was flat by a laser microscopy observation, it is assumed that this is the SSD. This result suggests that LLS can be a wafer inspection method that can observe SSD distribution. In addition, wafer inspection using LLS has demonstrated that it is possible to observe scratches, particles, and macrostep bunching. This method is anticipated to allow further optimization of the mechanical processing and thermal etching process prior to CVD epitaxial growth.