A statistical framework for laser-induced subsurface modification and cracking in 4H-SiC

Laser slicing of 4H-SiC enables low-kerf wafer separation, but reproducible subsurface crack formation remains challenging because the modified layer is buried, defect-sensitive, and statistically variable. Here, nanosecond laser-induced subsurface modification and cracking in commercial n-type 4H-SiC are described probabilistically rather than through deterministic thresholds. Incident fluence, pulse-to-pulse pitch, and focal depth below the surface were varied systematically, and image-derived outcomes were classified as modification onset, crack onset, or stable crack formation. Weibull analysis was used to describe the probability of each outcome, while binomial confidence intervals and bootstrap resampling were used to quantify uncertainty. Modification formed within a comparatively narrow fluence band across all tested depths and pitches. Pulse pitch emerged as the primary parameter governing the transition from modification to cracking. At smaller pitch, stable cracking became probable within the same fluence interval as modification, whereas at larger pitch a statistically separable fluence range produced modification without subsequent cracking. Cross-sectional SEM supported the corresponding morphological progression from void-like or elliptical modifications to wedge-like, crack-forming inclusions. This combined statistical and morphological analysis captures both systematic parameter trends and excursions among nominally identical conditions, providing a basis for selecting more reproducible crack-forming process windows for 4H-SiC wafer slicing.