Synchrotron X-ray topography analysis of local damage occurring during polishing of 4H-SiC wafers

 Surface defects with a scratch-like appearance are often observed locally on 4H-SiC wafers after epitaxial film (epi-film) growth. Since optical microscopy has only revealed a very flat surface after chemo-mechanical polishing (CMP) and before epi-film growth, the origins of these scratch-like surface defects have remained unknown. Therefore, we investigated the generation mechanism of such surface defects by synchrotron Berg–Barrett X-ray topography. Although only highly flat surfaces are observed by optical microscopy, we found that damaged regions comprising lattice defects are often introduced locally during polishing in the subsurface region. These lattice defects are almost completely removed by hydrogen etching, a pre-process for epi-film growth; however, surface defects associated with step bunching are formed in such damaged areas of the wafer surface. It is clear that local surface defects develop into surface defects with a scratch-like appearance during epi-film growth.

Source:IOPscience

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