Rapid nondestructive evaluation of subsurface damage in SiC wafers via second-harmonic generation microscopy and femtosecond laser polishing

Single-crystal silicon carbide (SiC) is a key material for high-power and high-frequency electronic devices. However, its inherent brittleness makes it highly vulnerable to subsurface damage (SSD) induced during mechanical processing, which can severely degrade device performance and manufacturing yield. In this work, we present a non-destructive SSD characterization approach by integrating femtosecond laser polishing (fs-LP) with depth-resolved second-harmonic generation (SHG) microscopy. Correlative analyses with cross-sectional scanning electron microscopy (SEM) confirm that the SHG contrast is strongly correlated with defect depth and microcrack density. The fs-LP process effectively relaxes near-surface stress without additional anisotropic defects. Atomic force microscopy (AFM) analysis results show that the surface roughness after fs-LP is comparable to that achieved by conventional fine grinding. Furthermore, depth-resolved SHG measurements reveal similar Z-dependent intensity profiles for fs-LP treated and fine ground wafers, indicating comparable SSD distributions. This integrated fs-LP-SHG platform enables rapid, wafer-scale SSD assessment and provides a practical, non-contact alternative for process monitoring and optimization in SiC wafer manufacturing.