Model-Free Iterative Learning Based Trajectory Tracking Control Approach In Wafer Stage

Lithography machine is the key tool ofthe manufacture of the semiconductor indus-try and a sophisticated optical mechatronics system,and the multi-freedom high-accur,acy stage is the key system in the lithography machine.The performance of the stage system determine the efficiency and the quality of the exposure process directly.So,it would be valuable to develop.the control method of the stage system.So,to solve the two main problems-achieve precision rapid transition between adjacent exposure dies in the expo-sure process and hold the position precisely during exposure-in the stage system,this paper perform the research of optimal trajectory design,modelless iterative learning control and iterative learning based feedforward feedback control.First,we explain the structure and exposure process,and point out the trajectory design problem and control problem.In the experiment,we identify the syst.em dynamics.Second,we set the trajectory design condition according to the characteristic of the stepper,and design the trajectory from the point of minimizing the energy.According to the results in the experiment,this trajectory decrease the tracking error efficiently.Third,we formulate the control problem during exposure process,and propose an model free differential inversion-based iterative control method(MFDIIC).This method remove the repetitive disturbance in the stepper and therefore improve the tracking perfor-mance.The experiment results show that this method can achieve the precision tracking during the transition section.At last,to achieve precision positioning during the exposure process and improve the robustness of the proposed method,we combine the MFDIIC feedforward control with the robust feedback control,and design an optimal switch controller to remove the switching caused error.The experiment results show that this method can keep both rapid transition and precisely positioning during the whole exposure,and meets the requirement of the wafer stage motion during exposure.