Chemical-assisted laser ablation coupled with ultrasonic vibration for enhanced SiC wafer thinning

Abstract

Silicon carbide (SiC) outperforms silicon (Si) with its superior breakdown voltage and wide bandgap for high power devices. While laser ablation offers a cost-effective and safe solution to thin SiC wafers, which is critical to minimize on-state resistance and improve thermal management, its efficiency is hindered by persistent challenges: particle deposition and shielding. This study introduces an innovative hybrid via approach combining chemical-assisted laser ablation with ultrasonic vibration, achieving high-speed and high-quality SiC thinning. By integrating ultrasonic vibration and flowing potassium hydroxide (KOH) solution, the particle deposition and shielding can be avoided with accelerating chemical etching. Under the optimized processing parameters at an ultrasonic frequency (30–50 kHz) and solution flow speed (0–0.54 m/s), a high materials removal rate of 0.41 mm3/min is achieved, which is 46% higher than the laser wafer thinning in air. The method successfully thins a 350 μm SiC substrate to a thickness of 50 μm with a flat surface (Ra = 0.29 μm), which has potential for the high-speed and high-quality thinning of SiC wafers.