Dynamic Dispatching for FOUP Cleaning

In a semiconductor manufacturing facility (FAB), wafers spend the majority of their manufacturing life in Front Opening Unified Pods (FOUPs), and it is essential that the environment be as clean as, or cleaner than, that of the manufacturing floor. While manufacturing equipment are usually constructed to actively purge and exchange internal environment to fab atmosphere, the FOUP is a relatively static environment that can only equalize its environment with the ambient area of storage. Hence periodic cleaning of FOUPs is essential to ensure the wafers produced meet requisite quality. However, selection of the number of FOUPs for cleaning provides challenges to the WIP flow strategy, scheduling and dispatching decisions. In this poster, we will cover the generic options for FOUP cleaning, metrology and dispatching challenges. Subsequently we will discuss the various strategies considered and employed to achieve appropriate trade-offs between various factors with respect to dispatching.