Study On The Deflection Law Of Ultra-Precision Grinding Silicon Wafer

Integrated Circuit (IC) is the foundation of modern information industry and the information society. As the foundation of IC development and the ideal substrate materials of semiconductor chip, the surface quality of silicon wafer directly influences the performance, yield and life of IC device. Ultra-precision grinding is the key technology of silicon ultra-precision machining, which has high machining accuracy,high efficiency etc. Now the wheel used during silicon ultra-precision grinding is always diamond wheel, after grinding, the surface of wafer will inevitably appear grinding damage and residual stress, which lead to the wafer's deformation, affect the transport as well as the mechanical properties of silicon wafer and so on.In order to study the deflection law of ultra-precision grinding silicon wafer, this thesis analyzed the stress distributing bases on measuring the damage distributed law of grinding silicon wafer, and used ANSYS software analyzed the force of wafer during grinding.; According to elasticity theory, we conducted the theoretical research to the deflection law of ultra-precision grinding silicon wafer, and theoretical research is proved by experiments. This thesis mainly includes the following aspects:(1) Through the angle polishing tests, this thesis studied the distributed law of damage depth of grinding wafer along different crystal orientations and radical direction. We analyzed the effects of grain size of diamond wheel and with or without spark-out process on damage depth. The results showed that the damage depth increased with the growth of the grain size. With spark-out process, the damage depth of silicon wafer is almost the same along different crystal orientations and radical direction, and the damage is uniformly distributed on the ground wafer. The result also showed that with spark-out process, the processing stress is uniformly distributed on the grinding surface.(2)According the acting force between the vacuum cup and wafer during the process of ultra-precision grinding, and the distribution of processing stress, using the theory of elasticity this thesis established a mathematical model of wafer's bow deformation which is belong to small deflection. The result showed that the maximum deflection of the grinding wafer is connected with the damage depth, the processing stress and wafer's thickness, the wafer's deflection curvature is a parabola; Using ANSYS software verified the wafer's force and deflection curvature during and after grinding.(3)Through the experiments of wafer's ultra-precision grinding, we got the maximum deflection and deflection curvature of wafers with different thicknesses grinding by different diamond wheels, compound with the mathematical model. The experiments'results showed that this model could accurately forecast the maximum deflection of grinding wafers with various thicknesses, when the deflection of silicon wafer is small, the error is less than 5%, but when the deflection of silicon wafer is large, it would emerge a large error.