Capacity planning for a twin fab

A capacity planning system (CPS) is developed for a twin fab based on the assumption of infinite capacity. CPS consists of three major modules: WIP-pulling module, workload allocation and accumulation module, and wafer release module. To meet the master production schedule (MPS), the WIP-pulling module pulls WIP from the end of the process routine. The workload allocation and accumulation module then calculates the expected equipment loading in different time periods. If WIP cannot satisfy the MPS requirement, the wafer release module is used to determine the planned wafer start time and the start production fab. On the basis of experimental design, simulation results show that CPS can smooth equipment loading in different time periods and balance the workload between fabs.