LINEAR-CONTROL RULES FOR PRODUCTION CONTROL OF SEMICONDUCTOR FABS

We consider the problem of reducing the cycle time required for produc ing wafers at a given rate in high-volume single-product semiconductor fabs. Based on theoretical results, we propose a new method of input control that uses intersecting hyperplanes to decide when to release a new lot into the wafer fab. The release control rules constructed thu s are said to belong to the class of linear control rules. We provide numerical examples to demonstrate that our method gives nearly optimal results for flowline and probabilistic reentrant flowline models. We then propose the linear control rule called descending control (DEC) a nd give a hybrid simulation-optimization procedure for determining DEC rules in real-life settings. We provide numerical results for the up development fab model of Wein [31].