The separation mechanism of 4H-SiC dicing by continuous laser

The Silicon carbide (SiC) is the second hardest material for single crystalline materials, which is only softer than the diamond, and recognized as a super hard wide-bandgap semiconductor material. The cutting process of SiC is mainly done by the abrasives in diamond, which leads to low cutting efficiency, high loss of abrasives, and server cutting damage. Thermal Laser Separation (TLS) uses the thermal effect of laser irradiation to cause the uneven expansion of materials, and cause the dynamic tensile and compressive stress fields to control the crack expansion, and realize the material separation. TLS consists two steps, firstly pulsed laser or mechanical blade are adopted to form a starting point for the crack; secondly continuous wave laser is moving along the prefabricated trace to separation the wafer by guiding the crack propagation. The separation process is a controlled crack propagation process in brittle materials from the view of fracture mechanics. But there is still not enough understanding of the fracture mechanism and parameter optimization problem of SiC dicing with TLS.In this paper, to understand the separation process, we have established a finite element model with a prefabricated crack in ABAQUS. In the simulation operation, different powers are set from 8W to 15W. We obtained the temperature distribution law of SiC surface under different laser heat source parameters. The stress intensity factor of SiC prefabricated cracks under the action of laser heat sources was sorted out. The results demonstrate that the SiC fracture mode is type I fracture. By studying the law of the stress field distribution on the SiC surface and along the depth direction, We further understand the separation mechanism of 4H-SiC dicing by continuous laser.