Daily scheduling for R&D semiconductor fabrication

This paper presents the development of a daily scheduling tool, Electronic Research and Service Organization Fab Scheduler (ERSOFS), for a research and development (R&D) pilot line of semiconductor wafer fabrication. An integer programming problem formulation is first given, which captures the salient features such as high variety and very low volume, cyclic process flows, batching at diffusion machines, single mask for each photolithography operation, loop test and engineering splitting and merging of wafer lots. A solution methodology based on Chang and Liao´s approach [1994] for scheduling flexible flow shops is then extended to this class of problems. The solution methodology is implemented and validated in an R&D fab. Results indicate that ERSOFS efficiently generates schedules of high quality. The rescheduling function of ERSOFS provides fast and smooth adjustments of schedules to cope with the. high production uncertainties in an R&D fab. Analysis of the algorithmic properties demonstrates the potential of ERSOFS for application to larger fabs