The main methods for silicon wafer cutting include diamond grinding wheel cutting and laser cutting. Laser scribing is the process of using high-energy laser beams to focus and produce high temperatures, causing the silicon material in the irradiated area to vaporize instantly and complete the separation of silicon wafers. However, high temperatures can cause thermal stress around the cutting seam, leading to edge cracking of the silicon wafer, and are only suitable for scribing thin wafers. Ultra thin diamond grinding wheel cutting is currently the most widely used cutting process due to its low cutting force and low cutting cost.
Due to the brittle and hard nature of silicon wafers, the cutting process is prone to defects such as edge breakage, microcracks, and delamination, which directly affect the mechanical properties of silicon wafers. At the same time, due to the high hardness, low toughness, and low thermal conductivity of silicon wafers, the frictional heat generated during the cutting process is difficult to quickly conduct out, which can easily cause carbonization and thermal cracking of diamond particles in the blade, resulting in severe tool wear and seriously affecting the cutting quality.
Domestic and foreign scholars have conducted extensive research on silicon wafer slicing technology. Zhang Hongchun et al. established a regression equation between vibration and cutting process parameters, and used genetic algorithms to obtain the optimal process parameters for small vibration. They verified through experiments that the optimal combination of process parameters can effectively reduce spindle vibration and achieve better cutting results. Li Zhencai et al. found that the sawing force generated by ultrasonic vibration assisted slicing is smaller than that generated by single crystal silicon slicing without ultrasonic assistance. Through silicon wafer slicing experiments, it was verified that reducing sawing force by ultrasonic vibration can suppress the edge breakage of silicon wafers. Disco Corporation in Japan has developed a laser slotting process to address the problem of difficulty in cutting low-K dielectric silicon wafers using ordinary diamond blades. The process involves first cutting two fine grooves in the cutting path, and then using a blade to perform full slicing between the two grooves. This process can improve production efficiency and reduce quality defects caused by factors such as edge breakage and delamination. Fudan University's Lu Xiong et al. used laser slotting followed by mechanical blade cutting technology to cut low-k dielectric silicon wafer materials. Compared with direct blade cutting, the chip structure is complete and there is no metal layer peeling or flipping phenomenon, but the process is cumbersome and the cutting cost is high. Yu Zhang et al. found that by increasing the damping ratio of the blade rotation process, the vibration phenomenon during high-speed rotation of the tool can be reduced to a certain extent, thereby improving the slotting performance and reducing the size of the broken edge. However, they did not conduct in-depth research.
Single slicing, which means completely slicing the silicon wafer in one go, with a slicing depth of 1/2 of the UV film thickness, as shown in Figure 4. This method has a simple manufacturing process and is suitable for cutting ultra-thin materials. However, during the cutting process, the cutting tools are severely worn, and the edges of the cutting blades are prone to chipping and microcracks, resulting in poor surface morphology of the cutting edges.
Layered slicing process, as shown in Figure 5. According to the thickness of the cutting material, a layered feed method is used for cutting in the depth direction. Firstly, perform slotting and cutting, using a relatively small feed depth to ensure that the tool is subjected to less force, reduce tool wear, and minimize cutting edge breakage. Then, cut to the position where the UV film thickness is 1/2.
