Using discrete event simulation to analyze the impact of job priorities on cycle time in semiconductor manufacturing

In the development and the manufacturing of semiconductors, wafer lots, which are groups of semiconductor wafers, are assigned different processing priorities based upon the required delivery time of these lots. In process development, experimental data is required which may necessitate the use of higher processing priorities on some lots so that the development of the process can proceed in a timely manner. Similarly, in manufacturing, customer requirements may dictate the use of higher priority lots to meet committed delivery dates. This paper uses the semiconductor manufacturing line simulator, ManSim/X, to analyze the impact of different percentages of "hot" lots on the cycle times of two different products that are in the manufacturing line. Rules-of-thumb can then be developed in allocating the amount of lots released which can contain a higher priority that do not significantly impact the overall cycle time of the product.