Suppressing kerf loss based on multi-focal approach for 4H-SiC laser slicing

Picosecond laser processing has emerged as a key technique for SiC wafer slicing, while it faces large kerf loss and surface roughness due to the high peak power. To address this challenge, we propose what we believe to be a novel multi-focal laser slicing method for efficient slicing of 4H-SiC enabled by an aberration-free non-iteration hologram generation method. Numerical simulations demonstrate high uniformity in multi-focal distribution, which contributes to reducing longitudinal damage. Furthermore, the effects of varying focal points and focal gaps conditions on the internal modification during laser slicing are experimentally investigated. After separation, the interface morphology, surface roughness, element distribution, and Raman spectroscopy are characterized. Experimental results demonstrate optimal slicing performance under 4-focal conditions with a 20 µm focal gap, yielding a wafer separation strength from 24.8 MPa in single focus to 7.6 MPa by 4-focal method and a total surface height variation of 10.7 µm. Furthermore, a 6-inch 4H-SiC ingot is sliced to validate its potential of industrial use. This method not only enhances the potential of hard brittle material slicing but also has broader application in laser microfabrication, 3D printing and waveguide fabricating.