Production-flow-value-based job dispatching method for semiconductor manufacturing

In a wafer manufacturing system, the value added to a particular product at a station may differ significantly from that added to a different product at the same station. If an enterprise concentrates mainly on generating profits, throughput becomes a poor performance measurement for a manufacturing system. Job dispatching rules based on maximum throughput no longer guarantee maximizing profit. Hence, profitability would be a good alternative measurement. The main purpose of this study is to develop a production-flow-value-based job dispatching rule (PFV) by the theory of constraints (TOC) for wafer fabrication. This study derives a TOC cost estimation method and a profitability estimate of a WIP-wafer lot. Jobs are then prioritized based on their profitability. Thus the PFV job dispatching rule is developed. For comparison, two job dispatching rules, MCR and MBS, are also arbitrarily selected to perform simulations. The simulation results reveal that the proposed PFV maximizes the production flow value, while MCR and MBS do not.