| Summary: | 碩士 === 國立交通大學 === 工業工程與管理系 === 87 === In wafer fabrication, the material of wafer and machine cost is expensive. To increase the wafer yield, defective wafers produced during the process need to be repaired as possible. However, rework of wafer is only allowed in the photolithography area of a wafer fabrication factory. If any defective wafer produced during the process which is not in the photolithography area ought to be scrapped. In addition, it is necessary to consider some important performance measures in a wafer fabrication factory such as WIP level, production cycle time, product due date…etc. Therefor, this study studies several rework strategies and dispatching rules which are often used in a fabs. The proper rework model is then suggested.
In this study, five rework strategies and five conventional dispatching rules are discussed. The five rework strategies are: 1.hold the mother lot while the child lot is reworked, and then complete the lot before moving it to the next location. 2.proceed the mother lot, and introduce a new child lot into the facility after finishing rework. 3.proceed the mother lot, and introduce a new lot composed of numerous child lots when a predefined number of wafers have accumulated. 4.proceed the mother lot, and add the reworked wafers to the next mother lot of the same product. 5.proceed the mother lot, while reworking the child lot immediately and completing the lot in some latter process. Five dispatching rules: FIFO, EDD, SPT, SRPT, and CR+ are used. A simulation model is developed to determine the performance of the combinations of rework strategies and dispatching rules.
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