As a third-generation semiconductor material, silicon carbide (SiC) possesses unique properties. SiC has a wide bandgap, high thermal conductivity, high saturated electron drift velocity, strong radiation resistance, and excellent thermal and chemical stability. These characteristics give it unique application advantages in high-temperature, high-frequency, and high-power power electronic devices and RF devices, making it promising for use in rail transportation, new energy vehicles, high-voltage power grids, 5G communications, aerospace, and defense military fields.
The surface quality of SiC wafers, used as device and substrate materials, is extremely important. After cutting SiC ingots, the resulting wafers have saw marks and mechanical damage layers on the surface, which increase wafer breakage rates and manufacturing costs, severely damage the wafer's crystal lattice, and affect SiC device performance. Damage layers, impurities, and micro-defects on the substrate surface can lead to high dislocation densities and lattice distortions in epitaxially grown thin films, placing stringent demands on epitaxial technology for achieving complete ultra-smooth surfaces. SiC substrates with excellent performance present great challenges in substrate preparation due to their high hardness, extreme wear resistance, brittleness, and tendency to crack. As the industry's requirements for wafer surface quality continue to increase, dedicated thinning equipment and high-efficiency grinding technologies have become key to SiC wafer processing.
Current mainstream technologies for flattening SiC wafer surfaces include grinding wheel thinning, mechanical lapping, mechanical polishing, chemical mechanical polishing (CMP), and chemical polishing. Among these, the grinding wheel thinning process is a core step. It uses fine-grit diamond grinding wheels to precision-grind SiC wafers, effectively removing the substrate damage layer, releasing residual stress, significantly improving wafer surface quality, and optimizing chip heat dissipation efficiency and low-power characteristics. It is an indispensable key step in SiC wafer manufacturing.
Diamond, known for its high hardness, good thermal conductivity, and chemical stability, is widely used in cutting and grinding semiconductor materials. In wafer thinning processes, to obtain a low-damage, ultra-flat, defect-free wafer surface, micro- to nano-sized diamond powders are typically used to make wafer thinning grinding wheels. Currently, the industry mostly uses monocrystalline diamond powders to produce thinning grinding wheels. However, these wheels have problems such as single cutting edges, insufficient overall sharpness, short service life, low processing efficiency, and poor precision during wafer thinning. Therefore, optimizing and modifying diamond abrasives has become a core research direction to improve grinding wheel sharpness, extend service life, and enhance processing results.
Wafer thinning plays an important role in semiconductor chip manufacturing. On one hand, thinning reduces the overall chip thickness, benefiting heat dissipation and integration; on the other hand, it reduces the thickness of the surface damage layer and surface roughness, relieves internal stresses accumulated inside the wafer from previous processes, and minimizes the degree of chipping of individual chips during dicing. Wafer thinning is generally performed using wafer rotation grinding. In the past, high-end domestic SiC wafer thinning heavily relied on imported ultra-precision equipment and diamond grinding wheels from Japan, which offer advantages such as high grinding efficiency, long life, high processing precision, and low breakage rates. Domestic equipment and grinding wheels struggled to meet the needs of high-end processes. With the rapid development of China's third-generation semiconductor industry, many domestic companies have begun independent R&D of thinning machines and grinding wheels, achieving significant breakthroughs in key indicators such as grinding wheel service life, wafer processing quality, and efficiency, thereby accelerating the pace of import substitution.