Research On Velocity Distribution Of Immersed Flow Field Based On Volume Illumination PIV Technology

Immersion lithography is different from traditional dry lithography.A layer of liquid with a refractive index greater than 1 is filled between the silicon wafer and the objective lens to improve the resolution and numerical aperture of the lithography technology.In the actual exposure process,if the flow rate of the immersion liquid is too small,the pollutants will be removed in the future,which will cause exposure defects.Therefore,the measurement of the flow velocity distribution of the immersion flow field is of great significance.Different from the traditional chip laser PIV technology,which can only measure the flow velocity in the immersion gap flow field region of the silicon wafer in the static state,a set of volume lighting PIV experimental system for measuring the flow velocity of the immersion flow field under different motion conditions of the silicon wafer is established.This solution introduces the objective lens static noise and silicon moving noise into the immersion flow field picture results.Therefore,this paper proposes an algorithm for extracting the immersion flow field flow velocity information,and finally obtains the global flow velocity information of the immersion flow field.Based on the above experimental system,the immersion flow field composed of the original immersion unit is experimentally studied.The results show that the core flow field velocity is too low.The influence of the injection port of the immersion unit on the flow field velocity distribution is investigated through simulation.The liquid injection orifice plate was improved,and it was experimentally verified that the flow velocity distribution of the new generation immersion flow field satisfies the flow velocity requirements in the actual exposure process.This article mainly completes the following tasks:(1)Design of experimental system for immersion flow velocity.According to the positional relationship between the projection objective lens,silicon wafer,immersion unit and the characteristics of the immersion flow field in immersion lithography,the light source module,camera module and immersion module are designed according to the experimental principle and actual working conditions analysis.Based on this,each component is selected and processed,and the entire experimental system is finally debugged.(2)Research on Algorithm of Extracting Flow Velocity Information for Immersion Flow Field.According to the complexity of the working state of the immersed flow field,a set of immersion flow field velocity information extraction algorithm is researched.According to the requirements of the step scanning of the silicon wafer in the actual working conditions,a pre-processing algorithm and a displacement information processing algorithm adapted to various working conditions are designed.Data post-processing algorithms.Coupled with the above algorithms,the algorithm interface is designed and the algorithm processing process can be monitored in real time.Finally,the algorithm test can be performed to convert the grayscale information of the particles in the picture into the immersion flow field velocity information to meet the design requirements.(3)Experimental study and analysis of distribution characteristics of immersion flow velocity.The experimental research was conducted on the original immersion flow field,and the flow velocity distribution characteristics of the immersion flow field under the static state of the silicon wafer were analyzed.The factors that affect the flow in the core flow field of the immersion unit are simulated through simulation,and the immersion unit is improved based on the experimental results.The flow velocity distribution of the new generation immersion flow field is verified experimentally,and its time and airspace characteristics are analyzed to meet the special requirements.Finally,the velocity characteristics of the immersion flow field at different scanning speeds of the silicon wafer were experimentally studied.