Matheuristics for Qualification Management Decisions in Wafer Fabs

In this paper, a qualification management problem arising in semiconductor wafer fabrication facilities (wafer fabs) is studied. The stepper machines, a common bottleneck in many wafer fabs, must be qualified to process lots of different families. A qualification time window is associated with each stepper and family. It can be reinitialized as needed and can be extended by on-time processing of lots from qualified families. Fast heuristic approaches, among them a Greedy Randomized Adaptive Search Procedure (GRASP), are proposed to solve large-sized problem instances using a small amount of computing time. The qualification decisions modeled by binary decision variables are made by heuristic procedures that exploit the problem structure while the real-valued quantities for each family and stepper are computed using linear programming. Computational experiments based on randomly generated problem instances are conducted. The results show that the proposed matheuristics are able to quickly provide high-quality solutions.