Research On Construction And Control Method Of High Speed And High Precision Pneumatic Image Quality Compensation System

The lithography projection will produce thermal aberrations during the working process,which will affect the imaging quality and processing efficiency.As the processing line width of the lithography machine shrinks,the thermal aberration generated by the objective lens system will also increase,which in turn will limit the improvement of the lithography machine technology.Therefore,in order to compensate for the thermal aberration in the objective lens system,it is meaningful to study an effective image quality compensation system.On the basis of system design,a control method that can achieve high-speed and high-precision image quality compensation must be developed so that the accuracy and efficiency of image quality compensation could be improved.In this project,an image quality compensation system for the Z5 astigmatism generated during the working process of the projection objective lens is developed.In addition,it presents a control method to implement the high-speed and high-precision control for the designed system and makes verification for the control effect and image quality compensation ability through experiments.Firstly,to realize the image quality compensation of Z5 astigmatism,this project implements the overall image quality compensation system,which mainly includes the air supply system,drive system,control system and pneumatic image quality compensation mechanism.Combined with the special application occasions of the lithography projection objective system,the demand analysis of the air supply,the control and the driving system is carried out and the corresponding system construction is completed.As required of Z5 astigmatism for lens deformation,the pneumatic image quality offset machinery is produced,and the construction of the image quality offset mechanism is improved by combining the finite element simulation.Since it is impossible to directly measure the final image quality surface shape compensation result,the equivalent control index of the high-speed and highprecision pneumatic image quality compensation control is deduced through the analysis system and experiments.An ideal mechanism modeling of the main pneumatic image quality compensation system is carried out,which includes the air pressure control valve,gas pipeline,restrictor hole,and bellows.Through the open-loop system identification experiment,the open-loop response characteristics of each part of the pneumatic image quality compensation system are obtained.Combining the system's open cycle reply characteristics,the identification of unknown factors of mechanism model is completed,and obtain the corresponding transfer function model of each part.With comparison of the simulation results of the system model and the open cycle response results of the actual system,the accurateness of the built model is proved with condidence.According to the open-loop response characteristics of the system,PID control,internal model control,and a cascade control strategy combining the PID control and internal model control are selected as the control methods of this system.The control principle,parameter adjustment principle and closed-loop stability of the three control modes are analyzed.Sum the controller and feedback link based on the system's open cycle modelling and simulation.Also,the full-closed cycle control simulations of the three controllers and their optimized controllers in the continuous domain are carried out respectively.Furthermore,according to the different placement positions of the feedback sensors,the semi-closed loop control simulations of each control strategy are also carried out.Finally,the discrete DSP control program is written,and carry out the physical control experiment.The developed cascade control strategy which combines the PID control and internal model control can implement the high-speed and high-precision pneumatic image quality compensation control.And the ability of the designed image quality compensation system is evaluated through the interferometer.It is proved that the system can realize the compensation of Z5 astigmatism.