Abstract
Queue time constraint refers to constraint that the elapsed time between two processes must be contained within a set time period in order to maintain the quality of the work pieces. Although many studied queue time constraints in semiconductor manufacturing, few discussed multiple queue constraints applied on consecutive manufacturing processes. The situation appears more frequently with the introduction of recent advanced processes. The research proposed dispatching and a lot releasing methods for a section of manufacturing processes under multiple queue time and batching constraints. First, an algorithm and associated software was developed to calculated the earliest lot releasing time that can assure non-violation of queue times and satisfy lot batching requirement of the work pieces in the observed manufacturing section. Second, a dispatching method based on waiting time allocation concept, at the beginning of the manufacturing section, and FIFO method for the ensuing processes is proposed. Simulation results show that this “section-wise” dispatching method performs better to some other commonly used dispatching methods such as First-In First-Out(FIFO), Global FIFO, Earliest Due Date(EDD), and Critical Ratio(CR) methods in all three performance indices: Target hit rate, average throughput and average cycle time.