Structural Analysis And Parameter Optimization Of Immersion Lithography Flow Field

Immersion lithography is based on traditional dry lithography technology,a liquid with larger refractive index is substituted for the original air between the projection objective and the silicon wafer.Immersion lithography can improves the resolution of the system.Although the introduction of immersion liquid improves the resolution,it also brings some other problems.As a part of the optical system,immersion liquid should keep its optical properties uniform and stable,which puts forward high requirements for the flow field of immersion.In this paper,the effects of structural parameters in immersion flow field on the flow in the exposure area and the stress distribution of one-side injection and one-side recovery immersion flow field have been studied.The valuable reference will be provide for design optimization and parameter setting of immersion flow structures in the future.The main research contents are as follows:Study on the influence of the asymmetry change of the circular opening angle and the width of the injection port and the recovery port on the flow field of the exposure area: On the basis of the structure parameters of the 193 nm immersion lithography machine,the circular opening angles and the width of the injection port and the recovery port are changed asymmetrically.The average velocity,velocity variance,average pressure and pressure variance in the middle surface of the exposure area under various circular opening angles and width of the injection port and the recovery port have been obtained by numerical simulation,the optimal combination of the circular opening angle and the width of the injection port and the recovery port has been obtained through comparative analysis.Study on the influence of fluid height and injection pressure on the flow of the exposure area: On the basis of optimal structure parameters of injection port and recovery port,the effects of flow field height and injection pressure on the flow in exposure area have been studied.The variation of average velocity,velocity variance,average pressure and pressure variance of flow in the exposure area under different flow heights and injection pressures has been obtained by numerical simulation.Through comprehensive analysis,the influence of flow field height and injection pressure on the flow in the exposed area has been analyzed.Study on the stress distribution of the single side injection / single side recovery immersion flow field: The variation of surface shear stress and normal stress with injection velocity,scanning velocity,height of flow field and liquid viscosity have been studied by simulation.It can provide reference for controlling the parameters of immersion flow.The theoretical formula of the surface shear stress under the objective lens in the flow field has been deduced and compared with the simulation results.The variation trend is similar.