Effect of anisotropy on deformation and crack formation under the brittle removal of 6H-SiC during SPDT process

Monocrystal SiC is representative of the third generation semiconductor materials, the efficient process technology of 6H-SiC wafer have always been a hot topic. Developing a SPDT processing method based on brittle removal mode with controllable surface/subsurface damage is an important approach to solve the processing difficulties of 6H-SiC.

This work aims to analyze the brittle removal process and fully explain the brittle separation behavior and deformation mechanism of 6H-SiC. The micro-scale crack propagation and the effect of anisotropy on crack distribution during machining process are investigated.

Large-scale molecular dynamics simulation was used in this work.

Under the condition of brittle removal, shear fracture occurs in the front area of tool tip. Shear plane is high-index surface, independent of slip system. The location of tensile fracture is the cleavage plane of hexagonal system, and the fracture surface is composed of step-like joint planes or perfect plane structures. Cracks with self-healing capability appear in the area behind the tool when the surface to be machined is basal plane. When the surface to be machined is not basal plane, a large number of dislocations or cracks remain in subsurface region. Under brittle removal mode, a large amount of plastic deformation appears as well, and deformation mode is related to processing scheme.

The brittle removal behavior of 6H-SiC under SPDT process has obvious anisotropy. Basal plane is more suitable for brittle removal of 6H-SiC without residual damage such as sub-surface cracks. The crack behind the tool generated by cleavage fracture can be repaired by itself. Fracture behavior is not related to dislocation. The processing method parallel to the c-axis can cause the generation of a large number of surface cracks. The (011¯0)/[21¯1¯0] and (112¯0)/[11¯00] mode is the best way to achieve plastic removal of 6H-SiC during SPDT process.