Synchronizing control of reticle and wafer stages using iterative learning control

To study reticle and wafer stages' moving synchronously during their exposure process, an iterative learning synchronization control method was proposed. A macro-micro control structure was chosen to achieve high bandwidth and tracking precision, and the actuators were voice motor and linear motor. The dynamic model of the reticle stage was established. A synchronization controller was designed based on the master-slave control structure, and the wafer stage was chosen as the master system and the reticle stage was the slave system. A 2-order open-loop type synchronization learning law was designed based on iterative learning control method and the convergence in the iteration domain was proved. Simulation results show that the synchronization learning method can reduce the synchronization error evidently. The maximum synchronization error and the move mean difference decrease along the iterative times, reducing by 45.12% and 36.84% in the fifth iterative respectively.