Experimental study on rolling and brittle fracture to single crystal silicon and sapphire by diamond cutter wheel

Rapid partitioning of integrated circuit chips is a key process in semiconductor device manufacturing. Usually, a fixed single-point diamond tool blade is used for scribing and cutting. However, the process can result in irregular cracks and damage chip circuits. Therefore, for two chip materials, i.e., single crystal silicon and sapphire, a 2.5 mm diameter diamond cutter wheel was used for rolling brittle fracture processing experiments. We analyzed the stress distribution under different machining processes and discussed the effects of the cutter wheel geometry and process parameters on crack extension and the rolling brittle fracture quality of different materials. The results show that the concentrated tension stress at the cutter wheel edge end generates and expands micro-cracks, which gradually shape micro-cutting marks in the rolling direction, leading to the final brittle fracture. However, this produces lateral cracks that make it easier to break the brittle fracture edge. Under a suitable tension stress, edge breakage is as low as approximately 1 μm and the brittle section quality is high. In addition, the greater the hardness and fracture toughness of the chip material, the smaller the cutter wheel angle and the greater the rolling pressure. When the rolling pressure of single crystal silicon is 0.015 MPa, the tensile stress at the edge contact is approximately 100 MPa, the rolling pressure of sapphire is 0.095 MPa, and its tensile stress is approximately 350 MPa, crack expansion of the fracture section after rolling and brittle fracture is relatively uniform, and the quality of the fracture surface is optimal. Finally, the experimental result showed that the quality of integrated circuit chips cut with the diamond cutter wheel with a micro-serrated structure is better. © 2022, Science Press. All right reserved.