Study On Simulation And Test Methods Of Immersion Liquid Squeeze Film Force In Lithography Machine

The immersion lithography machine reduces the lithographic feature line width and increases the optical numerical aperture by filling immersion liquid(usually pure water)between the projection objective and the silicon wafer.The immersion control unit that realizes the liquid return and hermetic sealing is mounted on the main substrate through a precision vibration damping-positioning system.The micro-vibration of the wafer stage and the immersion control unit is transmitted to each other by the immersion liquid in the micro slits and forms a disturbance to each other.As the decrease of lithographic feature line width,the motion of the lithography machine and the measurement system are more sensitive to the effects of vibration.Explaining and reducing the dynamic turbulence of the immersion liquid is one of the keys to the development of high-end lithography machines.In this thesis,the 28-14 nm immersion lithography machine requires that the dynamic force is less than ±0.2N in the small slit.Considering the vertical and roll micro-vibration of the immersion control unit relative to the silicon wafer,and developing theoretical analysis and experimental research on the dynamic force of liquid film.Firstly,based on the N-S equation and the continuity equation,a numerical model of the circular plate squeeze film is established.For two typical conditions of vertical vibration and roll vibration between immersion control unit and wafer table,the liquid film thickness and vibration frequency are analyzed.The influence of other factors on the turbulence of the immersion liquid clarifies the law that the immersion liquid disturbance dynamic increases nonlinearly with the increase of the disturbance frequency and decreases nonlinearly with the increase of the liquid film thickness.Secondly,in order to verify the correctness of the theoretical analysis of liquid membrane disturbance under vertical and roll vibration,the test device with bandwidth of 120 Hz,liquid film thickness of 0.09~0.5mm,vertical perturbation amplitude of 1?m,roll perturbation amplitude of 0.04 mrad and positioning accuracy of 2nm are designed based on a high-precision Nano-positioning platform.The structural characteristics of the test device were identified based on numerical simulation analysis and experiment,and the dynamic characteristics of the optimized micro-disturbance test device were verified.Finally,the perturbation dynamics experimental study of the extrusion liquid film transfers under vertical and roll disturbances was carried out.It is found that the numerical calculation is consistent with the experimental results when the thickness of the liquid film is greater than 150?m,and the error does not exceed 5%.The error between the numerical calculation and the test result increases with the decrease of the liquid film thickness,and has nothing to do with the frequency.At a working film thickness of 100?m,the vertical perturbation error reaches 12% and the roll perturbation error reaches 20%.The possible causes of the error between the numerical calculation and the test were analyzed,and the correction coefficient related to the thickness of the liquid film was proposed based on a large number of experimental data.The research method proposed in this thesis lays a foundation for the establishment of a precise squeeze liquid film model in the immersion lithography machine.The designed experimental device provides good experimental conditions for subsequent research.