Origins of Ultrafast Pulse Laser-Induced Nano Straight Lines with Potential Applications in Detecting Subsurface Defects in Silicon Carbide Wafers

The inspection of silicon carbide (SiC) wafer quality has attracted considerable attention because internal microstructure defects are challenging to detect in production lines. Expensive and destructive methods are usually employed to detect dislocations and stacking faults inside SiC wafers. Fast optical methods to monitor internal defects are in demand. In this work, an ultrafast pulse laser was used to address this issue. The formation of surface nanostructures under the ultrafast laser processing of SiC wafers was explored systematically. This study discovered the origins of a typical surface nanostructure to the subsurface dislocation structure, called low-energy laser-induced nano straight lines (LLINSs), which forms under low-energy ultrafast pulse laser irradiation on a SiC wafer. The specific laser fluence ranges to form grooves, laser-induced periodic surface structures, LLINSs, and their hybrids were identified. The formation of LLINSs required an ultrafast laser (pulse width 280 fs) energy density less than 0.224 J/mm 2 , whereas that of pure LLINSs required a small range of 0.1–0.08 J/mm 2 for SiC. LLINSs and their surrounding microstructures were observed using scanning transmission electron microscopy to identify their origin, which is related to the subsurface dislocation structure. Molecular dynamics analysis revealed that the subsurface defect area has a high energy level, which can facilitate amorphous transformation under the irradiation of an ultrafast laser, and the amorphous area had a tendency to evolve into LLINSs. Thus, subsurface lattice defects can be detected optically. This work opens new ways to detect the subsurface quality of semiconductor wafers in a green and sustainable manner.