New methodology of dynamic lot dispatching: required turn rate

In a semiconductor manufacturing fab with production-to-order type operation, hundreds of devices and various processes are managed. To provide short cycle time and precise delivery to satisfy customers´ expectation is always the major task. The difficulties encountered are complex process and product mix, unscheduled machines down time and equipment arrangement. How to dispatch lots effectively has become a very important topic in handling manufacturing. A dispatching algorithm named “Required Turn Rate (RTR)” is developed. According to the level of current wafers in process (WIP), RTR algorithm revises the due date for every lot to satisfy the demand from Master Production Scheduling (MPS). Further to calculate the required turn rate of each lot based on process flow to fulfill the delivery requirement. RTR algorithm determines not only due date and production priority of each lot, but also provides required turn rate for local dispatching. Therefore, local dispatching systems of each working area will dispatch the lots by using required turn rate to maximize output and machines utilization