Multiproduct Lot Merging–Splitting Algorithms for Semiconductor Wafer Fabrication

This paper focuses on a lot merging-splitting problem in a semiconductor wafer fabrication facility in which a relatively large number of wafer types are produced according to orders with different due dates. In the fab, two or more lots can be merged into a single lot if routes and all processing conditions of the lots are the same for a number of subsequent operations, and the merged lot is split into the original lots at the point where the routes or processing conditions become different. We suggest lot merging-splitting algorithms to reduce the total tardiness of the orders and the cycle times of the lots. The suggested algorithms are evaluated through a series of simulation experiments and the result shows that the algorithms work better than a method used in a real fab.