| Summary: | 碩士 === 中華大學 === 科技管理學系(所) === 95 === Over the past decade, wafer fabrication has become more complicated and lengthened the product queue time. To ensure final product yield, engineers need to set up queue time limits, named “time constraint”, for particular machines during wafer processing. Time constraint problems are more serious when the lots released from a batch workstation which often causes the peak workload on the downstream serial workstation. Both time constraint and batch-serial process occur in the furnace area of semiconductor fabrication. There is no doubt that time constraint will influence the manufacturing efficiency and turn into a new challenge to wafer fabrication. Under the time constraint environment, the peak workload will be a critical problem and hurt the performance of downstream workstation seriously. This paper applied GI/G/m queuing theory to develop a capacity determination model for batch-serial process. By this queuing network model, the expected waiting time between batch-serial processes can be estimated. Managers can also determine the capacity through the setting of expected rate of over time constraint. Furthermore, we analyze how the arrival smoothing of the upstream batch workstation will impact on the downstream serial workstation through our capacity determination model, such as waiting time. The result showed that it can effectively decrease the waiting time on the downstream serial workstation through increasing the upstream batch machine numbers and decreasing the batch size. It also implied that increasing the number of downstream serial machines is not the only way under the batch-serial process with time constraint environment. Therefore, the investment function of batch-serial process equipment with time constraint can be established and support managers for investment decision.
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