The Multi-Motion-Overlap Strategy to Minimize Time between Continuous Exposure Scans for Wafer Stage

During the exposure process, the transitional time between continuous scans does not produce production efficiency in which no scanning occurs. This inefficiency increases the total time to manufacture a chip on a wafer and limits the productivity of wafer in a production process. To optimize the transitional step time, we investigated the motion trajectory planning along the scanning direction for wafer stage during the exposure scanning process and introduced multi-motion-overlap strategy (MMO). The switch points of the step-move and scan-move were obtained by the theoretical analysis with MMO strategy, which did not violate the constant velocity phase and the limitations of acceleration and velocity along trajectories. The simulation results of the total time consumed between two continuous scans under the four different exposure field sizes are following: the MMO strategy enables the total time reduction 4.82%, 2.62%, 3.06% and 3.96%, compared with the conventional motion planning method, and 2.58%, 0.76%, 1.63% and 2.92% compared with literature method, respectively. The above theoretical analysis and simulation results illuminate that the multi-motion-overlap strategy can effectively minimize the transitional step time between continuous exposure scans and further to increase the wafer fabricating productivity.