Process mechanism of ultrafast laser multi-focal-scribing for ultrafine and efficient stealth dicing of SiC wafers

Silicon carbide (SiC), with its wide bandgap and high thermal conductivity, is considered a next-generation semiconductor material, which is driven by fast growth in energy-efficient and high-performance power electronic systems. Due to the ultra-high hardness of SiC, the traditional machining methods often led to large kerf width, crack, and high roughness on cleaved surfaces. Here, we report an ultrashort, pulsed laser-enabled stealth dicing (SD) process with an unprompted self-focusing effects, featuring excellent processing quality and efficiency. The nonlinear self-focusing effect was verified by finite element analysis. The nonlinear self-focusing effect induces multi-focus internal ablation along the laser propagation direction that generate multiple parallel modified layers. This phenomenon enables a laser-induced modified structure with a high aspect ratio up to 9.85 under a single-pass scribing. Significantly, a laser-induced modified zone with an ultra-narrow thickness of less than 8 μm and a smooth cleaved of minimal surface roughness of 224 nm Ra were manufactured in the ultrashort pulsed laser SD process with 6-pass laser scribing in a 330 μm-thickness 4H-SiC wafer. This result is a significant improvement in efficiency and quality compared to the existing SD process in the industry.