Analysis for Steady Schedule Convergence Against Random Time Disruptions in a Dual-armed Cluster Tool

Cluster tools are single-wafer processing systems widely used in semiconductor manufacturing. These tools typically operate under a steady regime, where the 1-cyclic schedule is the most desirable for maintaining stable and efficient production, as it ensures uniform quality and higher yield. However, time disruptions, such as process time delay, can destabilize the system, potentially leading to deviations from the 1-cyclic schedule. This study identifies the threshold of time disturbances that allow natural recovery to a 1-cyclic schedule without increasing cycle time. Furthermore, we show that dynamically adjusting start time of robot tasks contributes to system stability, ensuring consistent productivity despite disturbances. Our work lays the theoretical groundwork for a dynamic wafer loading control method that adapts to varying disturbance levels, ensuring stable and efficient tool operation.