Experimental investigation on crack evolution and separation strength in 4H-SiC slicing by sub-nanosecond laser

Abstract

Compared with wire sawing technology, laser slicing technology has been considered a more advantageous technique for slicing SiC wafers with the advantages of small kerf loss and high efficiency. How to realize laser slicing of SiC with low separation strength and low damage remains a current challenge. In this paper, semi-insulating SiC slices with a separation strength of only 0.04 MPa and a damage layer thickness of only 5 μm were realized using a sub-nanosecond laser. The crack nucleation mechanism was delved into by analyzing the morphology and composition of the modified layer, and the influence of laser processing parameters on crack propagation was systematically studied. Tensile tests were performed on samples with varying crack states to uncover the relationship between crack state and separation strength. The results indicate that the damage layer comprises graphite and amorphous silicon, with secondary processing being the key factor in the nucleation of cracks on the cleavage surface (0 0 0 1) plane. Separation strength minimizes when the interval matches the crack-tip stress field boundary. And the feasibility of large-area processing was verified on 6-inch ingots.