Silicon carbide (SiC), an emerging semiconductor material, is known for its high thermal conductivity, wide bandgap, high breakdown field, and high electron mobility. These properties make it one of the most researched semiconductor materials. Due to these characteristics, silicon carbide has widespread applications in substrates, epitaxy, device design, wafer fabrication, and more.
Metal Friction-Induced Grinding Technology
Metal friction-induced grinding technology is based on the chemical action induced by metal friction. This process involves the continuous generation and removal of a reaction-altered layer, which enables high-speed removal of silicon carbide.
Although silicon carbide has a very high Mohs hardness, it is unsuitable for processing ferrous metals. This is because silicon carbide decomposes at high temperatures, with carbon and silicon atoms diffusing into the metal, forming metal silicides and unstable metal carbides. These substances decompose during the cooling process, leading to significant wear. Based on this, it is inferred that pure metals can react chemically with silicon carbide under certain conditions.
In experiments, the carbon face of silicon carbide substrates often remains nearly undamaged, while the silicon face shows numerous crystal defects such as cracks, dislocations, stacking faults, and lattice distortions. The material removal rate when using iron to friction the carbon face of silicon carbide is 330 µm/h. When pure nickel is used to friction the silicon face, the removal rate increases to 534 µm/h.
This method is still in limited research, primarily focusing on small-scale silicon carbide processing, but it holds great potential in SiC substrate polishing and thinning SiC wafer manufacturing.
Sol-Gel Polishing Technology
Sol-gel polishing technology is an efficient, green polishing method that uses semi-solid abrasives and flexible substrates. The flexibility of the soft matrix allows for the "conformal" effect of abrasives, achieving ultra-smooth surfaces with low defect density on extremely hard semiconductor substrates. This method combines chemical and mechanical actions, effectively polishing hard semiconductor substrates without causing significant surface or sub-surface damage.
Compared to traditional CMP (Chemical Mechanical Polishing), sol-gel polishing technology can significantly reduce surface roughness in a short time and achieve high material removal rates. The soft matrix’s flexibility allows for polishing at lower pressures, reducing stress on both the workpiece and equipment, and decreasing abrasive wear and particle loss, extending abrasive lifespan.
Abrasive Scratching-Induced SiC Water Reaction Polishing Technology
Abrasive scratching-induced SiC water reaction polishing technology is an advanced material processing technique primarily used for precision processing of hard and brittle materials like silicon carbide.
This technology utilizes the scratching effect of abrasives on the surface of silicon carbide, combined with water reactions, to improve material removal efficiency and surface quality. By controlling the "conformal" effect of abrasives, non-crystalline silicon carbide is generated on the surface of SiC, which reacts with water to form soft silica, which is then removed by further abrasive scratching.
At the nanoscale, the surface of silicon carbide substrates becomes amorphous under repeated mechanical action of diamond or similar pressing tools. The reaction between amorphous silicon carbide and water generates silica. Factors such as load, contact state, speed, and temperature affect this process, which can significantly improve processing efficiency and surface quality while minimizing crack formation.
Conclusion
Current chemical mechanical polishing (CMP) methods for processing SiC substrates are important but have low processing efficiency, with material removal rates as low as 0.5 µm/h. In contrast, metal friction-induced grinding and abrasive scratching-induced SiC water reaction polishing can achieve material removal rates of 300-500 µm/h.
Research in this area is still limited, and further optimization in surface treatments and material selection is required. However, reaction-based polishing technologies, mainly driven by mechanical forces, hold promise for significant advancements in SiC substrate processing in the future.