The processing accuracy of semiconductor slicer is affected by various factors, mainly including equipment performance, cutting process parameters, wafer material and pretreatment, etc. The following is a specific analysis:
Equipment performance
Motion control system: driven by a linear motor and equipped with a high-precision grating ruler, it can achieve nanometer level interpolation operations, such as the Siemens 840Dsl CNC system. The high-resolution encoder of the servo drive ensures minimal speed fluctuations, thereby ensuring the accuracy and stability of the motion.
Positioning accuracy: Positioning accuracy refers to the accuracy of the device in determining the cutting position, which can be achieved at the nanometer level through linear encoders and laser interferometers. Some models can reach ± 0.1 μ m, ensuring that the cutting path perfectly overlaps with the cutting path area of the wafer.
Repetitive positioning accuracy: reflects the stability of the equipment's motion system. After adopting a closed-loop control system, the repeatability can be controlled at a lower level. For example, the Mitsubishi Electric MGK series can control the repeatability within ± 0.08 μ m.
Blade or chopper quality: The radial runout of the blade can affect the cutting accuracy. The spindle dynamic balancing technology can control the blade eccentricity within a certain range. For example, the Tokyo Precision DFD8510 model uses an air bearing spindle to reduce the runout to 0.3 μ m. For cleavers, the degree of wear can also affect the accuracy of fragmentation, and regular testing and replacement are necessary.
Cutting process parameters
Cutting speed: Excessive cutting speed may lead to unstable cutting force, resulting in uneven or even broken edges of the chip; If the speed is too slow, it will affect production efficiency and may cause thermal damage to the wafer due to long-term heat accumulation.
Cutting depth: It is necessary to accurately control the cutting depth according to the thickness and material characteristics of the wafer. If it is too shallow, the chip may not be completely separated, and if it is too deep, it may damage the fine structure inside the chip.
Feed rate: The feed rate should be matched with the cutting speed and cutting depth to ensure the stability and accuracy of the cutting process, otherwise it may generate significant mechanical stress, leading to chip breakage or deformation.
Wafer Material and Preprocessing
Wafer material characteristics: Different semiconductor materials have varying hardness, brittleness, and thermal sensitivity, which can affect the cutting effect. Silicon wafers are relatively hard, while materials such as gallium nitride are more fragile, and different process parameters and cutting methods need to be used during cutting.
Surface quality of wafer: The cleanliness of the wafer surface directly affects the cutting effect. If there are particles or chemicals remaining on the surface, it may cause the cutting path to deviate from the predetermined track, increasing the risk of chip breakage. In addition, the fixing method of the wafer can also affect the cutting accuracy, and unstable fixing may cause displacement of the wafer during the cutting process.
Environmental factors: Changes in temperature and humidity may affect the condition of wafers and equipment, and excessively high temperatures may cause wafer material expansion, affecting cutting accuracy; Low humidity may lead to static electricity accumulation, adsorption of dust and other impurities, thereby affecting cutting quality. Therefore, maintaining a constant temperature and humidity environment is crucial for ensuring the processing accuracy of semiconductor cutting machines.