Study On Slurry Distribution And Polishing Mechanism In Megasonic Vibration Assisted Polishing

Microchips are of great significance in the field of global science and technology,and can be called the “brain” of intelligent devices.As the substrate material of the chip,the surface quality of the silicon chip determines the performance of the chip.Based on megasonic vibration assisted silicon wafer chemical mechanical polishing process,the one-dimensional contact model and the distribution characteristics of slurry in megasonic vibration assisted polishing are analyzed.According to the distribution of slurry,the simulation and experimental analysis are made,and the megasonic vibration assisted chemical mechanical polishing mechanism is comprehensively analyzed.Firstly,the key elements of megasonic vibration assisted polishing are analyzed,including megasonic vibration polishing head,slurry and polishing pad.The working principle of megasonic vibration polishing head is analyzed in detail based on finite element method and laser vibration measurement experiment.The acoustic pressure and radiation pressure produced by megasonic vibration in slurry layer are studied.On this basis,the contact model and one-dimensional distribution of slurry in megasonic vibration assisted polishing are analyzed.The influence of megasonic vibration on the flow velocity of slurry is studied by using multi-physical field simulation technology.The experiments are carried out to study the influence of megasonic vibration on the diffusion flow of slurry from the edge of silicon wafer to the central region and the influence of megasonic vibration on the diffusion flow of slurry.The variation of effective polishing particles and the volume removed by a single polishing particle are investigated.The mechanism of vibration in megasonic vibration chemical mechanical polishing is analyzed.The results show that the vibration energy of the megasonic vibration polishing head is concentrated in the central area of the working face.Because of the vibration of the megasonic vibration polishing head,the polishing liquid layer in the polishing area is subjected to acoustic radiation pressure.The flow experiments of slurry show that the slurry will accumulate in the center and edge of the polishing pad,but less in the center of the silicon wafer.Megasonic vibration makes slurry in the pore of the polishing pad flow faster,diffuse to contact area and participate effectively in polishing.Megasonic vibration increases the number of effective polishing particles in the rough peak of pad,so that the removal rate of the central region of the silicon wafer is similar to that of the edge,and improves the surface quality of the silicon wafer.