Abstract
Abstract
With the requirements of physical vapor deposition and chemical vapor deposition processes, twin-cluster tools are widely used in the current wafer fabrication. Cycle scheduling ensures that wafers have the same quality, however, twin-cluster tools involve resource coordination between two tools, which makes cycle scheduling more sophisticated. A steady-state cycle scheduling problem of twin-cluster tools with a complete concurrent processing module is studied, considering the wafer residency time constraints. First, a Petri net model is constructed to describe the process of twin-cluster tools under a steady state with the wafer residency time constraints and the complete concurrent processing module, and a control strategy is proposed to avoid the system deadlock. The sufficient conditions for the system to reach the highest efficiency are obtained by analyzing the workload of the processing module and the robot task, and an algorithm is developed to obtain the robot schedule. Finally, examples are verified about the effectiveness of the algorithms.