Thermal stress manipulated nano-crack growth for high-quality and low Kerf-loss SiC slicing via orthogonally polarized dual-beam nanosecond laser irradiation

Abstract

High-quality laser slicing of SiC substrates with low kerf-loss remains highly challenging because nanosecond laser processing is accompanied by heat accumulation, non-uniform thermal stress, and uncontrolled crack propagation. Here, an orthogonally polarized dual-beam nanosecond laser strategy is proposed for controlled nano-crack formation and low-damage slicing of 4H-SiC substrates. Experiments, microstructural characterization, phase-field analysis, and molecular dynamics simulations show that the overlapping dual beams regulate polarization-dependent shear stresses, localize structural modification, and guide stable nano-crack propagation along the designed slicing plane. At a laser fluence of 104 J/cm², a continuous internal nano-crack layer with a characteristic width of approximately 250 nm is formed. The separated surface exhibits an average surface roughness (Ra) of 5.87 nm, while site-specific TEM and HRTEM analyses reveal localized amorphization, stacking-fault-rich regions, and plastic-slip bands near the modified plane. These results establish a direct link between polarization-dependent thermal-stress regulation and defect-assisted nano-crack propagation, and identify an optimal processing condition for low-damage SiC slicing. This work achieves stress-regulated nano-crack growth and provides a promising method for the high-quality fabrication of wide-bandgap transparent crystals.