An approach to fuzzy control of target function in consideration of equipment flexibility and workload in semiconductor photo lithography operations

Cycle-time is an important indicator for semiconductor wafer fabrication. In semiconductor factories, the flow of each wafer contains 300–900 processing steps, in which the most critical layer operation is in the photolithography tools. To achieve the target of cycle time more effectively, accurately modeling dispatching rule for each critical layer becomes more and more important. Existing approaches to rescheduling generally consist of hot lot, process queue time for quality and tool efficiency to maximize tool utilization, which is not enough to operate in a highly dynamic and unpredictable environment. This paper attempts to present a systematic design methodology for fuzzy control of a class of nonlinear systems. An example of a semiconductor wafer fabrication line in Tainan is given. The experimental results demonstrate the effectiveness of the proposed fuzzy control of target function.