A better choice-a fuzzy logic based lot sequencing decision support system for operators in a job shop fab with reentrant process flows

Significant reduction of cycle times can be achieved by removing barriers. Cross training, cross functional teams, leveled production, starts control, bottle-neck management and so on are the well known ways that help to improve the process. No matter how well this matter is dealt with, disturbances will occur in any waferfab. The only way operators can still influence the fabs cycle time performance is by making the right choices when selecting which equipment to operate first and which lot(s) to process next. This is a difficult task, since many factors should be taken into account, particularly in mixed volume, mixed process, mixed product fabs with reentrant process flows. As part of the research program ABC, A Better Choice, a fuzzy logic based lot sequencing decision support system has been developed and implemented. Heuristics as well as theory were used in its design. The DSS has brought significant benefits in a fully loaded fab in terms of more outs, while retaining a good cycle time.