Fast Heuristics for Making Qualification Management Decisions in Wafer Fabs

We discuss qualification management problems arising in wafer fabs. Steppers need to be qualified to process lots of different families. A qualification time window is associated with each stepper and family. The time window can be reinitialized as needed and can be extended by on-time processing of lots from qualified families. Due to the NP-hardness of the qualification management problem, heuristic approaches are required to tackle large-sized problem instances arising in wafer fabs in a short amount of computing time. We propose fast heuristics for this problem. The binary qualification decisions are made by heuristics while the real-valued quantities for each family and stepper are determined by linear programming. We conduct computational experiments based on randomly generated problem instances. The results demonstrate that the proposed heuristics are able to compute high-quality solutions using short computing times.