弹性磨抛轮加工硅片面形预测模型及试验验证OA北大核心CSTPCD

Silicon wafer is the most widely used substrate material for integrated circuits.Ultra-precision grinding is widely used in the back thinning and flattening of silicon wafer and it can achieve high dimensional accuracy,fast material removal and relatively small wear.The elastic Grind-polishing wheel is a new type of non-woven structure grinding tool with low elastic modulus and ultra-fine abrasive grains,which can obtain high surface and subsurface quality grinding wafers.It is prepared by ultra-fine ZrO2 abrasive particles and low elastic modulus wool fibers.The surface roughness of the silicon wafer after grinding can reach 0.45 nm,and the subsurface damage depth is about 67 nm.It has significant advantages in processing efficiency,process integration and environmental friendliness,and has great development potential.However,as one of the important evaluation indexes of the surface,the surface shape rule of the workpiece is rarely studied.The material removal of the silicon wafer during the grinding process is uneven and the surface profile of the workpiece is poor.The work aims to analyze the affecting factors of the surface of the workpiece in the grinding by the elastic Grind-polishing wheel and optimize the processing parameters to obtain good surface shape.In previous studies,the surface shape rule was only speculated based on the distribution density of the abrasive trajectory on the surface of the silicon wafer,and the actual material removal amount could not be calculated to obtain an accurate surface shape.In this study,by establishing the elastic Grind-polishing wheel abrasive trajectory model based on the elastic Grind-polishing wheel speed,silicon wafer speed,eccentricity and other processing parameters,combined with the establishment of considering the calculation of Grit-cutting depth and calculating the material removal depth of different radial positions of the silicon wafer,the prediction method of material removal non-uniformity in silicon wafer grinding was proposed.The surface shape prediction model of silicon wafer ground by Grind-polishing wheel based on material removal depth was developed,and the accuracy of the prediction model was verified by grinding tests under different speed ratios.The surface shape simulated by the surface shape prediction model is the same as the silicon wafer after the elastic Grind-polishing wheel grinding test,both of which are convex,and the PV value increases with the increase of the speed ratio.When the speed ratio was 1,the PV value of silicon wafer after grinding was 0.54 μm,and the PV value calculated by the simulation model was 0.49 μm.When the speed ratio was 5,The PV value of silicon wafer after grinding was 2.12 μm,and the PV value calculated by the simulation model was 2.38 μm.The prediction error between the PV value of silicon wafer after grinding and the PV value calculated by the model is less than 13%.It shows that the model can successfully predict the surface shape of ground silicon wafers,the influence of processing parameters on the surface shape of silicon wafer can be analyzed.Surface shape prediction model analysis shows that the speed ratio has an effect on the surface accuracy of silicon wafers,and with the increase of the speed ratio,the surface shape of the silicon wafer deteriorates continuously.In the actual processing,a smaller speed ratio should be selected to obtain a better surface shape of the silicon wafer.The model has certain guiding significance for selecting appropriate grinding parameters to obtain ideal silicon wafer surface.