Machine grouping algorithm for stepper back-up and an empirical study

Considering the limitations of the operation cost and the flexibility need of the manufacturing, the wafer was unable to expose in the same stepper from layer to layer in the real setting. In addition, the lithographic systems also require appreciate back-ups to avoid the yield loss as the equipment fault or shut-down for maintenance. This study aims to develop a machine group algorithm for the stepper and thus propose appropriate back-up based on the similarity of systematic overlay errors and residuals. The results are confirmed with judgments of domain experts and thus validated this approach