| In the positioning stage system of the EUV lithography machine,a large balance mass is used to absorb the reaction force of the wafer stage actuators,thereby reducing the vibration caused by the actuators’ impact on the vacuum chamber(base frame).The balance mass is supported by a flexible hinge and uses eddy current dampers for energy dissipation.This thesis explores the design of the balance mass isolation system and uses simulation models to evaluate the isolation effect for parameter selection and subsequent solution improvements.A dynamic simulation model of the wafer stage and controller and a dynamic simulation model of the balance mass isolation system were built using Simulink and Multibody components in Simscape(physical model).The wafer stage model and the balance mass isolation system model were combined into a whole to provide a motion trajectory for the wafer stage,and the spring damping force output by the balance mass isolation system was obtained through simulation.According to the modal superposition principle,a flexible dynamic simulation model of the vacuum chamber in the form of state space equations was built in Simulink.A dynamic simulation model of the main plate isolator and a flexible dynamic model of the main plate were built.The wafer stage model,the balance mass isolation model,the vacuum chamber flexible model,the isolator model,and the main plate flexible model were combined in the order of vibration energy transfer to build a complete rigid-flexible coupling simulation model for evaluating the balance mass isolation effect.A motion trajectory was provided for the wafer stage,and the final vibration amplitude at the suspension point of the laser interferometer on the main plate was simulated.Using the mean square value of the output force of the balance mass isolation system as the optimization target,genetic algorithms were used to optimize the damping coefficients in the X and Y directions.The simulation results showed that the root mean square(RMS)of the output force of the optimized balance mass isolation system was reduced by 52.56% in the X direction and 58.99% in the Y direction compared to the original design.On the basis of optimizing the damping coefficients,a dynamic vibration absorber was added to the balance mass.The simulation results showed that the RMS of the output force in the X and Y directions was reduced by 19.5% and 36.5% after the dynamic vibration absorber was added.Compared with the original design,after damping coefficient optimization and vibration absorber installation,the RMS of the output force in X and Y direction of the vibration isolation system of the balance mass decreases by61.8% and 74%,and the RMS of the vibration acceleration in X and Y direction on the main plate decreases by 56.86% and 62.13% respectively. |
