High Efficiency And Low Damage Process Of Ultra-precision Grinding Silicon Wafer

Silicon wafer is the most important substrate material in the IC industry.Nearly 95%of IC chips are made on silicon substrate.In order to meet the requirements of packaging technology for wafer thickness,the wafer grinding process needs not only high efficiency to remove machining allowance,but also requires high surface/subsurface quality of silicon wafer.In order to improve the machining efficiency of silicon wafer and reduce the surface/subsurface damage of silicon wafer,the grinding performance of diamond grinding wheel with different grain size was studied in this paper;A special grinding wheel for wet mechanical chemical grinding was designed and its grinding performance was studied.The research results have important guiding significance for the realization of high efficiency and low damage of silicon wafer.The main research contents and conclusions are as follows:(1)The grinding experiments of diamond wheels with different grain sizes were carried out.The surface morphology,surface roughness and subsurface damage of silicon wafer were detected and analyzed by scanning electron microscope(SEM),three-dimensional surface profiler(ZYGO)and ultra depth of field microscope,According to the results of experiment and theoretical model analysis,the grinding wheels of rough grinding group are#400,#600,#1500,and the grinding wheels of fine grinding group are#2000,#3000,#5000,#8000.(2)Aiming at the surface layer damage of silicon wafer grinding by diamond wheel,and the problems of high grinding temperature and more grinding dust in the current mechano-chemical grinding technology,a wet soft abrasive grinding wheel is designed in this paper.The grinding wheel uses Si O₂as abrasive grain and resin as bond.The grinding performance of soft abrasive grinding wheel was studied by testing the surface roughness,surface/subsurface damage and material removal rate of silicon wafer.By detecting the chemical composition of silicon wafer surface before and after grinding by soft abrasive grinding wheel,the chemical reaction between abrasive,monocrystalline silicon and water was analyzed.The results show that the new designed soft abrasive grinding wheel can obtain high surface/subsurface quality and realize low damage machining of silicon wafer.(3)According to the above research basis,new process are proposed to improve the silicon wafer machining efficiency and reduce the silicon wafer surface/subsurface damage:rough grinding with#400 diamond grinding wheel,fine grinding with#3000 diamond grinding wheel,and mechanical chemical grinding with newly developed Si O₂soft abrasive grinding wheel.The new process is used to grind silicon wafer.The surface with nanometer roughness is obtained,and no subsurface damage is observed.Moreover,the machining efficiency is doubled compared with the previous process,and the high efficiency and low damage machining of silicon wafer is realized.