Study On High Efficient Polishing Method For Ultra Thin Sapphire Wafer

The high cost of the material of sapphire highly limits its application.Only from the perspective of the cost of material,it is true that the sapphire wafer is the thicker the better.However,processing the ultrathin sapphire wafer is much more difficult than normal wafer.It is easy for ultrathin sapphire wafer to break during polishing time.In order to solve the breaking problem for stress concentration during polishing time,this project put forward a way of water film adsorption and spacing ring to clamp the ultrathin wafer.The research work and results of this project include:1)From the perspective of intersurface physics,study on the adsorption mechanism of the model of ultrathin sapphire wafer,water,substrate.The relationship between the adsorption force and the material of substrate and the surface roughness of substrate is grasped.And this paper concluded that only from the perspective of physical mechanics,substrate should be selected in small contact angle(strong hydrophily),strong ductility material.The surface roughness of substrate should make the substrate be hydrophily.2)From the perspective of adsorption ability,study on the feasibility of water film adsorption clamping by experiment.The results of the experiment shows that it is feasible to fixed position by water film adsorption,only from the perspective of adsorption ability.45# steel is more suitable for the material of the substrate than glass.Judging whether the water film clamping is feasible or not should mainly consider the tangential adsorption force.The experiment of tangential adsorption ability reveals that identifying the surface roughness of the substrate should mainly consider the surface roughness of the sapphire wafer.3)The uniformity of force of the ultrathin sapphire wafer under water film adsorption is analyzed by ANSYS simulation software.The parameters of the load and width of spacing ring and the interval of the spacing ring and wafer on the distribution of the contact stress of the sapphire wafer are overall simulated and analyzed,achieving the method of selecting the related technology parameter of spacing ring.The simulation results show that when the ratio of the load on spacing ring and wafer being 2 can make the contact stress of the ultrathin wafer uniform.4)By the experiment of the rate of breaking wafer and the experiment of ultrathin sapphire wafer water film adsorption clamping polishing processing,the results show: the wafer which is clamped by water film can endure more polishing pulling force,and the polishing efficiency is higher.Besides,the quality of the surface is better under water film clamping for ultrathin sapphire wafer.Studying the experiments on substrates of different materials can conclude that the influence of the material of substrate on removal rate is little,so it can be eliminated.The influence of the material of substrate on processed ultrathin sapphire wafer is heavy,and 45# steel substrate can make the wafer achieve the best flatness.This paper grasps some key technologies of the way of water film adsorption clamping(e.g.the design of spacing ring),and also solve the difficult problems of stress concentration which makes the ultrathin sapphire wafer broken during polishing and the low polishing efficiency,achieving the goal of high efficiency polishing for ultrathin sapphire wafer by mechanism analyzing and experiment studying.