Research On Temperature Field And Warpage Of Silicon Wafer Based On Flexible Polishing

The functional substrate made of monocrystalline silicon and other crystals is an important substrate material for integrated circuits.The quality of its surface has a direct influence on the yield,lifetime and performance of the device.In order to obtain the surface of super smooth and low damage crystal substrate during manufacturing,polishing is an indispensable process in the preparation of crystal substrate.At present,the polishing of the crystal substrate mainly adopts the rotary grinding method of hard grinding wheel.In the process of machining,with the increase of processing time,the surface temperature of crystal substrate rises gradually,the residual stress accumulates,which easily causes the warpage of crystal substrate.In view of the above problem,a flexible pneumatic polishing method has been proposed.Under the new polishing method,the temperature fild and warpage of silicon wafer polishing process is studied from three aspects: theoretical research,finite element numerical simulation and experimental research.The main research work of this paper are as follows:(1)Theoretical analysis of silicon wafer polishing temperature field and warpage deformation.Firstly,the material and mechanical properties of silicon wafers are analyzed to obtain the fracture law of silicon wafers on different crystal planes.Secondly,the theoretical analysis of the warpage of silicon wafers shows that the residual stress and temperature are the main factors affecting the warpage of silicon wafers.By simplifying the silicon wafer and using the Stoney formula,the mathematical relationship among the warpage,residual stress and temperature of the silicon wafer is obtained.(2)Numerical simulation analysis of flexible polishing method.The simulation results of the residual stress,temperature and warpage of silicon wafers under flexible pneumatic polishing are obtained by geometric modeling,mesh division and boundary conditions setting through ANSYS.(3)On the basis of determining the machining parameters,a flexible pneumatic polishing experimental device is built,and experimental research is carried out based on the simulation results.The temperature distribution of silicon wafers under different polishing time is investigated by using Fluke thermal imaging camera,and the temperature distribution of silicon wafers is obtained.The KEYENCE ultra-deep three-dimensional microscope is used to observe the polishing effect of silicon wafer.Under the condition of selecting different stages of green silicon carbide polishing in stages,the silicon wafer achieved a mirror effect,and the roughness dropped below 2.5?m.The experimental results show that the flexible polishing method can effectively overcome the warping deformation produced by the polishing of silicon wafers and improve the polishing surface accuracy.Finally,the overall research contents are summarized,and corresponding improvements are put forward for deficiencies.