Analysis On Hydrodynamics And Material Removal Rate Of Circular Translational CMP

With the fast development of semiconductor industry, the demands for precision and surface quality of wafer become higher and higher. Chemical-mechanical-polishing (CMP) has known to be the most effective planarization process that can give the required local and global planarity of wafers and widely used in the semiconductor industry.Circularly translational-moving chemical-mechanical-polishing is a new type CMP method. Its mechanism is the same as that of traditional CMP. The surface of the wafer is polished both by mechanical abrasion and by chemical erosion to achieve a global planarization. But circularly translational-moving CMP has the best kinematics conditions of polishing, and can obtain better work efficiency and quality than the traditional CMP method. The study of mechanism of circularly translational-moving CMP will be conductive to the actual processing of precision control, and increase efficiency of the production.Base on the kinematics relation of circularly translational-moving CMP, the mixed lubricating model and material removal rate model of circularly translational-moving CMP of partial-film contact were set up with consideration of pad deformation. The hydrodynamic model involves the average Reynolds equation, the contact equation, the elastic deformation equation, the fluid film thickness equation, the balance equations of load and moments. These model equations were calculated by the finite difference method, and the instantaneous 3-D distribution of fluid pressure, contact pressure, elastic deformation and the slurry film were simulated. The effects of applied load, pad velocity, rotation speed, pitch angle, rolling angle on fluid pressure, contact pressure, elastic deformation and the slurry film were obtained by analyzing the numerical results, and the effects of pad material parameters and shape parameters on fluid pressure, contact pressure, elastic deformation and the slurry film were further studied.Based on the mixed lubricating model, the material removal rate model of circularly translational-moving CMP was established. The relation of the quality and efficiency of polishing and the various parameters of abrasive particle was analyzed, and the influence of the procedure parameters on the efficiency of polishing was studied.Analysis of results showed there was fluid suction in a wide area in circularly translational-moving CMP process. It was caused by the change of the slurry film distribution because of the pad deformation. In the circularly translational-moving CMP, contact pressure can change gently from the center to the edge of wafer. So, circularly translational-moving CMP can achieve the best movement, and can improve the surface quality of the polishing.