Design of Dispatching Rule for Photolithography Area in Wafer Fabrication Factories with Rework Considerations
|關鍵字:||晶圓製造;黃光區;派工法則;重工策略;wafer fabrication;photolithography area;dispatching rule;rework strategy|
Semiconductor industry is one of the most leading edge industry in Taiwan. Generally, the process flow of wafer fabrication may contain 300~400 steps or operations. It is complicated and filled with uncertainties, like hot order, rework lot, machine down and so on. Therefore, the production planning and control in wafer fabrication is an tough issue. In wafer fabrication, the material cost of wafer is expensive. To reduce the cost and increase the yield of wafer fabrication, it is imperative to repair the defective wafers produced during the manufacturing process. However, repairing defected wafer will not only increase the WIP level but the flow time of rework lots as well. In wafer FAB, rework of wafer is only allowed in the photolithography area, where is the bottleneck of the entire wafer FAB. The objective of this research is to develop a dispatching rule concerned with rework for photolithography area. The dispatching rule considers two kinds of rework strategies: (1) hold the mother lot while the child lot is reworked and (2) process mother lot while the child lot is reworked, and complete the lot in latter process. We conduct experimental simulation and the results indicate that the dispatching strategy developed in this research can improve the production performance of wafer fabrication factories.