Research On High Precision Tracking Control And Interference Suppression Of Lithography Machine

Lithography is an important process in the production of semiconductor materials.Because of low cost,high sensitivity and high yield,maskless lithography equipments have broad application prospect in the integrated circuit manufacturing industry.As an important module of lithography equipment,the motion control system of wafer stage is carried out with silicon chip to complete the scanning exposure motion,so motion speed and tracking precision are directly related to the yield and quality of the core moment.This paper takes the wafer stage control system as the object to carry on the research work.First of all,the control problems of the wafer stage system are analyzed in detail from three aspects: high precision control,scanning trajectory influence and system interference suppression.These factors are pointed out that the platform has parameter perturbation,motor disturbance power,noise interference and other factors that are not conducive to tracking control.In view of the problem that the convergence of tracking error and exposure efficiency are seriously affected by the system overshoot which is easy to occur in the transition process,the optimal energy function is used to plan the trajectory of the transition process in the motion of the wafer stage.The system frequency response curve is obtained by scanning experiment,and the system transfer function is obtained by fitting the dynamic equation.Secondly,the principle and characteristics of model-free iterative learning control are analyzed,and the scheme of model-free iterative learning control to achieve high precision tracking control is designed.In order to improve the robust performance of the system and the convergence speed of iterative learning,the fuzzy control strategy is introduced to adjust the iteration factor on the basis of the model-free iterative learning control strategy.The experimental results show that the model-free fuzzy iterative learning control can effectively improve the convergence speed and tracking accuracy,and also has a good inhibitory effect on repetitive interference.However,under the action of non-repetition interference,the tracking error of the system increases obviously,and the oscillation of the tracking error in the iterative domain fails to converge to a stable state.Thirdly,aiming at the problem of the influence of non-repeatable disturbance on tracking accuracy in the system,the model-free fuzzy iterative learning control strategy based on disturbance compensation is studied.the disturbance compensation schemes of ESO and IDOB are designed respectively.ESO and IDOB are introduced into the control structure to estimate the system disturbance and feedback the estimated value to the control loop to achieve the purpose of disturbance suppression.in the experiment,the control strategy based on disturbance compensation can effectively suppress the influence of non-repetition interference on the tracking accuracy.Comparing the experimental results,it is concluded that IDOB has stronger suppression ability and higher tracking accuracy than the extended state observer.Finally,introduce the control system modules of wafer stage,the tracking control strategy mentioned above is implemented on the actual platform,the track tracking control experiment of the wafer stage is completed,comparative analysis of the experimental results,and the superiority of the model-free fuzzy iterative learning control with disturbance compensation is proved,which makes the tracking performance of the system obviously improved.