研究目的
Investigating the performance of several requalification strategies for stepper tools in semiconductor wafer fabrication facilities to ensure high-quality production with minimal additional qualification effort.
研究成果
The study demonstrates that some of the proposed requalification strategies perform well with respect to throughput and cycle time while requiring only a low additional qualification effort. The 'tailored (T)' strategy is identified as a desired compromise between production-related performance and qualification efforts.
研究不足
The study is limited to the stepper tool group in semiconductor wafer fabrication facilities. The impact of requalification strategies may vary with different qualification cost settings, failure durations, and lengths of replanning intervals.
1：Experimental Design and Method Selection:
A mixed integer linear programming (MILP) formulation is used to determine qualification plans. A discrete-event simulation framework is applied to assess the performance of requalification strategies in a rolling horizon manner.
2：Sample Selection and Data Sources:
The MIMAC I simulation model is used, which includes two products with highly reentrant process flows, 17 different families, and over 200 tools organized into 84 tool groups.
3：List of Experimental Equipment and Materials:
Six steppers in the stepper tool group, each lot contains 48 wafers, and a commercial solver CPLEX 12.1 is used for solving the MILP instances.
4：1 is used for solving the MILP instances.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The simulation stops at the beginning of each planning epoch to create and solve a new planning instance based on the shop-floor status. The simulation runs until the start of the next planning epoch, repeating this cycle until the end of the simulation horizon.
5：Data Analysis Methods:
The performance is assessed based on throughput (TH), average cycle time (ACT), average tardiness (AT), percentage of tardy lots (%TL), and the number of existing qualifications (QAvg).
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