Motion Control Analysis For A Wafer Stage Based On Multibody Modeling

Scanning lithography is one of the most important and complicated equipments for the Integrated Circuit (IC) manufacture, and wafer stage is one of the key subsystems of the lithography. There is a high requirement for the positioning precision, velocity and acceleration of the wafer stage. So research on the dynamical and control characteristics is very important for improving the precision of the lithography.After analyzing the mechanical components of the wafer stage, a multibody dynamical model is established using ADAMS and Simulink software based on the theory of multibody. The model is proven to be right by the comparison of vibration test and simulation. Frequency response functions in the motion orientation (in horizontal plane) of the wafer stage are examined. On the basis of frequency response functions, the dynamical characteristics of the wafer stage are analyzed, and how it will influence the design of controller is also pointed out.Combining the motion requirements and dynamical characteristics of the wafer, a control solution containing both feedback and feedforward is proposed. Firstly, the design specifications for the feedback controller are confirmed, and the PID controller and H∞controller are synthesized. Secondly, the acceleration trajectory signal is used for feedforward control. Finally, the model used for horizontal motion control of the wafer stage is set up, and the simulation results show that the H∞controller is better than the PID controller both in tracing error and positioning precision.A software used for the analysis of dynamics and motion control of the wafer stage is developed based the previous effort. Firstly, functions of the software are specified, and the software architecture is got. Secondly, the development of the software is reviewed. Finally, the process of analyzing of the dynamics and motion control of wafer is presented through a case, and the value of the software is also proved.