Vibration Isolation And Gravitation Compensation Of Plate Stage For TFT-LCD Lithography

Plate stage is one of the key subsystems in Thin-film Transistor-Liquid Crystal Display (TFT-LCD) lithography equipment. Precision and stability of the plate stage affect the throughput, overlay and imaging performance of the tool Compared with wafer stage in Integrated Circuit (IC) lithography tool, the moving range, motion speed and the reation force of the plate stage are larger, and the vibration isolation and motion control are much more difficult. In order to fulfill the performance requirements of plate stage, global active vibration control and local area vibration isolation are studied in this dissertation. Both structure and control parameters of the active vibration isolators are optimized to improve the performance of global active vibration isolation system (AVIS). Also, structure and controller of the gravity compensation isolators are designed for local vibration isolation.The dynamic model of the AVIS is deduced with theoretical derivation. The optimization method for the structure parmaters and the self-tuning method for the PID controller are also proposed. The stiffness model and the peak stress model of the pendulum are presented. In order to minimize the margin of the horizontal natural frequency between the actual values and the design value, its optimal structure parameters are obtained by using the sequential quadratic programming (SQP) algorithm with the constraints of the material stress and geometry sizes. The experiment results show that the relative error of natural frequency between the experiment value and the design value is less than10%. And a self-tuning method with3steps is proposed to tune the PID parameters of the controller, which is approved both by simulation and experiment.Gravity Compensation and vibration Isolator are used in the Local Vibration Isolation System (LVIS), and the dynamic models of LVIS including unit level and system level are established.The stiffness models of two types of GCI are deduced and the corrugated diaphragm type is chosen for LVIS. The stiffness model of corrugated diaphragm type GCI is verified by an experiment. The6-DOFs dynamic model of the LVIS is deduced, and their model natural frequencies are calculated with model decoupling method. The experiment result shows that the relative errors of the model natural frequencies between the experiment values and the calculated values are less than10%.A motion control method for the vertical directions of the plate stage is proposed. Three pneumatic force feedback loops are added to the positioning control loops in vertical directions, in order to eliminate the static force of the motors and reduce the heat generated by the motors when the gravity force of the payload is varied. Experiment results show that the vertical positioning performance isn't affected by the pneumatic loop, and95%of the static force of the Lorenz motor is compensated by the pneumatic loop.The vertical stage requires high precision positioning performance in Z/Rx/Ry/Rz directions, and the structure shows that strong motion couplings exit in Z/Rx/Ry directions. So the gain scheduling maxtrix and the gain balancing matrix are deduced for decoupling control of the vertical stage. The electro-mechanical simulation results show that the structure and the decoupling control method for the vertical stage fulfill the positioning its performance requirement.