TOOL PLANNING IN MULTIPLE PRODUCT-MIX UNDER CYCLE TIME CONSTRAINTS FOR WAFER FOUNDRIES USING GENETIC ALGORITHM

Tool planning is to determine the number of tools in each workstation for achieving some objectives. This paper formulates and solves a tooling problem in the context of multi-product mix, where the mean cycle time must be under a predefined target. Due to demand variation, a wafer foundry frequently faces the need to manufacture in various product-mix. Previous literature has addressed the issue of multiple product-mix, yet the cycle time constraint has not been considered. Cycle time is a key performance index for wafer foundries and should not be ignored in their tool planning. We propose a genetic algorithm based solution methodology embedded with a queuing analysis to solve the problem. Test examples reveals that the proposed solution greatly outperforms that obtained by a single product mix planning.