Vibration Analysis And Motion Control Of Ultra-precision Stage With Air-bearing For Lithography

Lithography is one of the most important and complicated key equipments for the Integrated Circuit (IC) manufacture. The ultra-precision stage is the important subsystem of lithography. Vibration analysis and precision control of ultra-precision stage with air-bearing is studied in this thesis.The ultra-precision stage is a six degree-of-freedom motion stage for precision positioning with high-speed. The vibration analysis of ultra-precision stage is difficult because the structure and the contact pattern of ultra-precision stage are complex. It is a challenge for control stystem to achieve precise positioning performance, because the precision of ultra-precision stage must reach 10nm. In the thesis, the vibration analysis is studied by the finite element (FE) method, and a control strategy is also discussed.In terms of the structure and working principle of the ultra-precision stage, the FE modeling methods for some key parts are discussed, and the FE model is set up. Based on the FE model, the vibration performance of ultra-precision stage is analyzed. The simulation results show that the precision of x,y,θz has been influenced by the vibration. The natural frequency caused by air is between 0 and 300Hz. On the basis of the study of the ultra-precision stage vibration performance, a simple model for control simulation is established.The planar motor which drived the ultra-precision stage is studied. The model of the planar motor is established. According to the requirement of control, the position decoupling and the force decoupling are discussed. In order to achieve the quick, smooth, steady, and precise positioning performance for ultra-precision stage, a trajectory of ultra-precision stage is designed. In terms of the control model, adopting the force decoupling of planar motor, a position/velocity PID control is designed to achieve high response ability, smooth, stable motion and high precision.The results of FE model simulation are verified by the experiments. Good agreement between the simulation results and experimental results is obtained, which indicats that the FE modeling methods are reasonable, the FE model is correct. The simulation results can be used for optimization design of the ultra-precision stage. The results of control simulation show that the proposed control strategy is usable and valid.