Dual-Step Laser Ablation and Polishing for High-Quality Microgrooves in Low-k Wafer Dicing

High-quality microgrooves are essential for wafer dicing of low-k dielectric stacks, where back-end-of-line layers are prone to thermal and mechanical damage. This work introduces a dual-step laser approach that combines UV nanosecond ablation with a low-fluence polishing pass to improve groove integrity. The ablation step defines the microgroove geometry, while the polishing step induces localized remelting to remove recast and microcracks and reduce roughness. Experiments on silicon wafers show that a polishing fluence of 10.6 J/cm² significantly lowers surface roughness by up to 70% without additional ablation. Profilometry and SEM confirm smoother groove bottoms and cleaner sidewalls. The method offers a scalable solution for producing high-quality microgrooves in low-k wafer dicing.