Crack control for efficient nanosecond-laser slicing of large-size 4H-SiC crystals

Due to the ultrahigh hardness of Silicon carbide (SiC), the traditional diamond wire sawing often led to large kerf width, crack, and high roughness on cleaved surfaces. By contrast, Laser slicing SiC is an efficient way to produce SiC wafers with reduced material loss and improving productivity. The key of laser slicing technology is the generation, propagation and connection of cracks. In this paper, the influence of the process parameters of laser-slicing N-type 4H-SiC with nanosecond laser, including laser output power, scanning speed, scanning-lines numbers and group spacing, on the crack is studied in detail. Finally, a simple, fast and efficient multiple-line overlapping laser-scanning strategy has been developed for laser slicing of large-size 4H-SiC ingots. The optimal laser processing parameters are obtained to separate a 6 in. 4H-SiC wafer and the slicing time of ∼18 min per piece is much less than that of traditional multi-wire cutting. After polishing the sliced 4H-SiC wafer, its geometric parameters and stress state were investigated and showed that nanosecond laser slicing had no discernible impact on 4H-SiC. The above results present a promising route and demonstrate the feasibility of nanosecond laser for low-cost and high efficiency slicing of large-size 4H-SiC wafer.