Research On Distribution Of Ultra-precision Magnetorheological Finishing Force At Semiconductor Wafer

Information technology is a high ground for technological innovation in the world,and it is also a high-tech field with the highest R&D investment,the most extensive application range,the most active innovation,and the strongest radiation power in the world.With the rapid development of the high-tech information industry,the market has put forward higher requirements for core technologies such as integrated circuits and the quality of finished products.Wafers are used as substrates for integrated circuits,and the quality and efficiency of the finished products of their manufacturing process directly restrict the development of the integrated circuit industry.There is an urgent need to accelerate the development of ultra-precision and high-efficiency wafer surface processing technology.The material of the wafer is generally a hard and brittle semiconductor material,which has the characteristics of high hardness,strong brittleness and stable chemical performance.The global ultra-precision flattening of the wafer is difficult and costly.Compared with traditional polishing technology,magnetorheological polishing technology has the advantages of high precision,high efficiency,almost no subsurface damage and easy control.During the process of ultra-precision magnetorheological finishing,the material removal rate of wafer surface material is directly related to the wafer surface polishing force distribution and abrasive particle velocity,but the research of wafer surface polishing force distribution during magnetorheological polishing is not comprehensive.Based on the in-depth study of ultra-precision magnetorheological polishing technology at home and abroad,this paper has carried out the following research work on the problem of wafer surface polishing force distribution in ultra-precision magnetorheological planar polishing:(1)Theoretical calculation of wafer surface polishing force for magnetorheological planar polishing.The principle of dynamic magnetic field magnetorheological plane polishing and the material removal process on the wafer surface were studied and analyzed;the velocity distribution of the magnetorheological polishing fluid on the wafer surface was solved based on the movement and relative positional relationship between the wafer and the polishing disk.Based on the theory of magnetic field,a magnetic field model of dynamic magnetic field is established,and the magnetic induction intensity distribution on the wafer surface at different times is obtained.The geometric characteristic parameters of the flexible polishing pad are extracted and quantified,and the model of the flexible polishing pad is established.Combined with the related theories such as hydrodynamics and Preston equation,the hydrodynamic pressure distribution on the surface of the magneto-rheological planar polishing wafer is derived and calculated.The positive pressure distribution on the wafer surface caused by the magnetization of carbonyl iron powder and the shear force distribution on the wafer surface in line with the conditions in this paper are thoroughly studied.(2)Simulation analysis of the polishing force of the surface of the magneto-rheological planar polished wafer.The magnetic field distribution was numerically simulated,the numerical results of the magnetic induction intensity were extracted,and the magnetic field data file was compiled and added to Fluent's magnetohydrodynamics(Mhd)module.Coupling simulation of magnetic field and flow field,the effects of processing parameters such as processing gap,wafer speed,polishing disc speed and excitation gap on the positive pressure and shear force distribution on the wafer surface were analyzed.The simulation results of the corresponding pressure distribution and shear force distribution on the surface of the wafer are extracted and compared with the theoretical calculation results,and the validity and accuracy of the theoretical model are initially demonstrated.(3)Experimental verification of the polishing force of the surface of the magnetorheological flat polished wafer.The ultra-precision magnetorheological plane polishing device was used as the experimental platform to carry out the magnetorheological plane polishing experiment.The study analyzes the transfer relationship between the polishing force of the wafer surface and the measurement results of the dynamometer,determines the experimental measurement scheme,and analyzes the experimental results to obtain the experimental value of the polishing force of the wafer surface.The experimental values of different process parameters after analysis and processing are compared with the established theoretical and simulation results to verify that the results have good consistency.