Simulation Study On Influence Factors Of Double Side Polishing Uniformity

Semiconductor silicon material is the main functional materials of the electronic information industry, especially of the integrated circuit industry, and the processing technology of silicon wafer has become the main driving force for the development of the electronic information industry in the world. With the increasingly diameter of silicon wafer and decreasing feature size of IC,a higher requirement to the planarization of silicon wafer is put forward. Double-sided chemical mechanical polishing is one of the most effective means in silicon wafer ultra-smooth surface machining. However, in the actual production, chemical and mechanical interact alternately, multiple variables interaction, the tiny change of variables will influence the contact relations among silicon wafer, polishing liquid and polishing pad,and the centrifugal force causes the polishing liquid and abrasive to distribute on polishing pad unevenly, which will lead to the edge over polishing and polishing unevenly. This not only resource is waste, production capecity is too low, but also IC performance is degradeg. In this paper, using monocrystalline silicon wafer as the processing object, based on the research background on the CMP uniformity, the influence of polishing speed, polishing pressure and inlet number on double-sided polishing uniformity is researched using chemistry,geometry,and computer simulation technology on the basis of Solid Works, FLUENT and MATLAB by means of theoretical analysis, numerical simulation and experimental study. The main research works are as follows:(1)The chemical reaction mechanism and material removal mechanism is analyzed in the monocrystalline silicon double-sided chemical mechanical polishing. Uniformity function based on the speed of the polishing disc is established on the basis of the Preston function,and the influence of polishing pressure polishing, liquid inlet number, polishing pad,temperature, polishing liquid pH value and abrasive particle size, etc.on double-sided polishing uniformity is analyzed.(2)Based on Solid Works and FLUENT, the 3D geometry model and flow field flow model of monocrystalline silicon double-sided chemical mechanical polishing are established,the boundary conditions are determined, and the influence of velocity, pressure and polishing fluid inlet number on the polishing uniformity is obtained by the simulation analysis.Simulation results show that: when the sum of wafer rotation speed and revolution speed is equal to the disc speed, double sided polishing uniformity is best; with the pressure increased,the double-sided polishing uniformity is decreased; with the polishing liquid inlet number increased,the double sided polishing uniformity becomes better, when the inlet numberincreases to a certain value, the polishing uniformity is unchanged.(3)Simulation results are verified through the experiment. under different polishing pad speed, polishing pressure and liquid inlet quantity, experiments are preceded in the double side chemical mechanical polishing equipment. Experimental results show that the simulation results are accurate and reliable.This paper not only has guiding significance to the actual production, but also provides reference for the more precise polishing of the single crystal silicon wafer.