Ultrafast laser-induced internal modifications and cross-scanning strategy for material-efficient 4H-SiC slicing

Laser-based sectioning has emerged as a game-changing technique for high-precision and material-efficient processing of silicon carbide (SiC) wafers. However, the fundamental mechanisms behind ultrafast laser-induced subsurface modifications remain poorly understood. This study investigates ultrafast laser-induced internal modifications in semi-insulated SiC wafers, with a focus on the effects of laser pulse energy and duration. Raman spectroscopy revealed that the modified SiC structure comprises crystalline SiC, amorphous SiC, amorphous Si, and amorphous C. Thermal stress analysis revealed distinct crack propagation patterns that vary with laser parameters. Two scanning strategies and spacing configurations were analyzed to optimize the stripping of SiC wafers. An internal laser cross-scanning method is proposed, enabling successful delamination of 4-inch SiC wafers and delivering key improvements: (1) a 30% reduction in peeling stress, (2) a modified layer height of ∼25 µm, and (3) surface roughness below 7.3 µm. This technique preserves up to 90% of the material compared to conventional diamond wire sawing, offering remarkable gains in both precision and material efficiency.