Study on Wear of Diamond Grinding Wheel in Silicon Wafer Self-rotating Precision Grinding
Author:Ren Qing Lei
In the rapid development of information networks,people are increasingly dependent on integrated circuit(IC).Silicon,as an excellent substrate material,is widely used in the IC industry.High quality wafer processing is the key to the initial manufacturing of the chip.Especially for the flattening of large-diameter silicon wafers,ultra-precision grinding is more effective than conventional processing.The use of cup-shaped diamond grinding wheel for silicon wafer grinding is a typical form of ultra-precision grinding silicon wafer.The grinding wheel is an extremely key processing tool in the process of silicon wafer self-rotation precision grinding.Whether the wheel performance is good or not directly determines the quality and economic cost of processing.The research on the wear of the grinding wheel used in silicon wafer precision grinding is of great significance for optimizing the grinding wheel performance,improving the precision grinding technology of silicon wafer,and promoting the development of the IC industry.This paper starts with the analysis of the mechanical theory of the micro contact state between the grinding wheel and the silicon wafer.The contact wear of diamond grinding wheel is studied by micro contact state simulation analysis and grinding wheel surface modeling analysis,and grinding experiments and observation verification.(1)First of all,from the macro stability in the grinding process of extracting silicon micro grinding wheel contact with silicon micro unit as the research object,assumptions,established an ideal model of micro mechanical contact.The decomposition of the mechanics model of contact force,to use contact Hertz theory of mechanics and the theory of cavity model,was analyzed to obtain the silicon wafer corresponding to the elastic and plastic stage load and the stress distribution,also to obtain the wheel in the micro unit corresponding stress distribution.Tangential analysis using the micro friction theory of the sliding friction force,superposition synthesis method to the load after the micro silicon and micro grinding wheel should contact the force in the process of unit distribution.Through the analysis of the stress distribution of the wheel contact points will occur in the process of the corresponding form of wear.(2)Secondly,the grinding wheel and the wafer micro contact is simplified,and established a three-dimensional body simulation model,the explicit non-linear finite element analysis software LS-DYNA of self rotating grinding micro process were simulated,on strength and strain stress process of silicon wafer and wheel micro element of finite element analysis,and with single particle pressure scratch test results were compared and verified the validity of the model.The results showed that the silicon materials under external force exists corresponding elastic rotor plastic-plastic turn brittle critical displacement and load;in silico plastic region to slide can produce plastic groove and uplift on the surface of the silicon chip,which belongs to the category of ductile regime machining.Grinding wheel micro unit wear form according to the simulation should force data to judge:under the simulated conditions,the grinding wheel micro unit grinding particle exists only wear;wheel micro unit bond breaking strength is less than the maximum internal stress critical value,easy to produce abrasive wear abrasion scaling;elastic modulus of bond on the bond generated rupture location effect.(3)Third,on the basis of macroeconomic wheel grinding particle random probability distribution and on the grinding wheel surface topography of the corresponding simplified modeling,and the results are characteristic parameters are compared and validated with grinding wheel actual observation,analysis of the model in different cutting depth of effective grains,superposition of the corresponding sand wheel micro stress unit of microscopic simulation data,a comprehensive analysis of the macro wheel will occur in the wafer grinding process of wear.Analysis results show that:in the current simulation of grinding parameters,macroscopic grinding wheel abrasive no rupture,only in the presence of abrasive wear;fracture strength of bond if too small,when less than that produced by the maximum internal stress the critical value,the bond interface prone to rupture,forming abrasive exfoliation and abrasion.(4)Finally,according to the analysis of theory and Simulation of wafer grinding experimental control,through cup diamond wheel grinding force experiment and wafer self rotating grinding experiment and the corresponding grinding wheel surface topography observation,analyzes the grinding force in grinding process change rules and wafer surface quality formation influences,of self rotating wafer grinding removal mechanism,grinding force and surface quality of silicon and wheel wear between the relationship between,to verify the theory and simulation analysis of wear.The analysis showed that the grinding force produced under the experimental conditions of abrasive wear off the surface of the grinding wheel to produce large area,mainly produces wear debris is adhesion wear.In this paper,the theoretical simulation and experimental research on grinding wheel wear of silicon wafer during self-rotating grinding are carried out.The theoretical analysis conclusion is consistent with the experimental research results.The research of grinding wheel wear is the bond between the preparation of grinding wheel and the grinding performance.The research of grinding wheel wear is the link between the preparation of grinding wheel and the research of grinding properties.The research results provide a theoretical basis for the preparation and selection of the grinding wheel used in silicon wafer precision grinding,and the improvement of the performance and quality of the grinding wheel.