Work-in-Process Balancing Control in Global Fab Scheduling for Semiconductor Manufacturing

This paper addresses the problem of controlling the Work-In-Process (WIP) in semiconductor manufacturing by using a global scheduling approach. Global fab scheduling steers scheduling decisions at work-center level by providing objective in terms of production targets, i.e. product quantities to complete for each operation and at each period on a scheduling horizon. A WIP balancing strategy is proposed to minimize the product mix variability in terms of throughput and cycle time. This strategy is enforced using a global scheduling optimization model which is formulated as a linear programming model. The global scheduling model is coupled with a generic multi-method simulation model for evaluation purpose. Computational results on industrial data show that the WIP balancing strategy provides a better control of the WIP in the system and helps to minimize product mix variability while maintaining high throughput.