Slicing of 4H‐SiC Wafers Combining Ultrafast Laser Irradiation and Bandgap‐Selective Photo‐Electrochemical Exfoliation

Abstract

Abstract High‐efficiency and low‐loss processing is the mainstay to reduce the cost and deepen the application of 4H silicon carbide (4H‐SiC) wafers in high‐power and high‐frequency electronics. In this study, the high‐yield slicing of 4H‐SiC wafers is realized by combining femtosecond laser irradiation and bandgap‐selective photo‐electrochemical (PEC) exfoliation. By combining light‐absorption measurements, micro‐Raman, and micro‐photoluminescence characterizations, it is found that the damage layer formed inside 4H‐SiC after femtosecond‐laser irradiation consists of amorphous silicon and amorphous carbon. This indicates that the femtosecond‐laser irradiation leads to phase separation in 4H‐SiC. The bandgap of the damage layer is 0.4 eV. Taking advantage of the different bandgap energies of the damage layer and the perfect 4H‐SiC region, the damage layer is removed from the perfect region of 4H‐SiC by using bandgap‐selective PEC etching. During the PEC etching, light‐generated holes can selectively oxidize and corrode the damaged layer with the assistance of the HF solution, and leave the upper and lower perfect 4H‐SiC layers being intact. The current work contributes to the development of the high‐yield and high‐throughput femtosecond laser slicing of 4H‐SiC wafers.

Keywords

• 4H silicon carbide wafers
• ultrafast laser slicing
• photo‐electrochemical etching