| Summary: | 博士 === 中原大學 === 工業工程研究所 === 96 === Process specifications in wafer fabrication require precise definition. Whether or not an operation can be worked at a specific machine depends on the machine’s ability, and this is the process capability constraint. Moreover, processing all the layers of a lot on the same stepper assures better yield rate, and this is the machine dedication constraint. The capability and dedication are specific constraints at photolithography of wafer fabrication that makes it difficult to obtain the optimal production plan in the real production environments. This research develops a Capacity Requirements Planning system considering equipment’s Capacity, Capability, and Dedication of (CRP-CCD) for semiconductor manufacturing fabs.
CRP-CCD consists of two major parts: Infinite Capacity Requirements Planning System (ICRPS) for multiple fabs and Finite Capacity Requirements Planning System (FCRPS) for single fabs. Based on an assumption of infinite loading, ICRPS determines the product mix for each fab by Order Assignment (OA) and Capacity Allocation (CA). Using Path Load (PL) concept, OA selects appropriate product mix for each fab and determines the loading occurrence times of each of the required capability of each order to better balance the equipment workload among various fabs, on various days, and across various equipment at various levels of demands by taking into account equipment’s capacity and capability at multiple fabs. CA uses Loading Ratio (LR) concept to select the machine used to process each order’s capabilities considering equipment’s capacity, capability, and dedication to smooth the loading among machines with the same capability. ICRPS can help fab engineers to arrange equipment capability, equipment backup and subcontract.
After the application of ICRPS, FCRPS is then used to develop an appropriate production plan for single fab. Based on an assumption of finite loading and by taking into account equipment’s capacity, capability, and dedication, FCRPS combines Backward Finite Loading (BFL), Maximum Minimum Capability (MMC), and Path Load (PL) to determine the release time and equipment capability for each lot to minimize Mean Absolute Lateness (MAL) of customer orders and the Standard Deviation of the Utilization of equipment with the same Capability (SDUC). FCRPS can help fab salespersons to negotiate with customers regarding order due dates.
Data from a real foundry fab are collected and used by simulation based on experimental design to evaluate the performance of CRP-CCD. The following conclusions are drawn from the analysis of simulation results. In ICRPS, OA based on Adjusted Release Time (ART) and PL can efficiently balance the equipment workload among various fabs, on various days, and across various equipments at various levels of demands. CA using LR can efficiently balance the equipment workload among different machines with the same capability. FCRPS combining BFL, MMC, and PL can efficiently balance the loading on various machines with the same capability and minimize MAL of customer orders. These findings demonstrate CRP-CCD can obtain the right production plan for semiconductor manufacturing fabs by assigning the right orders to the right fab and assigning the right orders to the right equipment with the right capability. Thus, CRP-CCD can help semiconductor foundry companies to obtain better equipment utilization, more balanced equipment loading among different fabs and also among different machines with the same capability, shorter manufacturing cycle time, better on-time delivery, and lower work-in-process.
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