Key factors in designing a manufacturing line to maximize tool utilization and minimize turnaround time

Today´s semiconductor manufacturing facilities require very expensive tools, with the total investment necessary to equip a production line approaching a half-billion dollars. Therefore, it is imperative to understand those factors that help to determine the number of tools to be purchased, their characteristics, and how they should be arranged to attain the most effective utilization of these assets. This paper shows that the imposition of a turnaround-time (TAT) requirement on a tool set/manufacturing line introduces additional constraints on tool operating characteristics. Tool availability, the time a tool is off line, and the number of tools per process now become key factors that must be used to determine the effective capacity and achievable turnaround time of a tool set/manufacturing line. The results of this work show how tool design and installation characteristics can significantly improve line capacity and reduce TAT. Some fundamental elements of designing a manufacturing line are also discussed, such as when tools should be arranged in a ´farmed´ mode (in close proximity because of process similarity and their independence from process flow) or a ´linear´ mode, (with dissimilar tools/processes arranged in close proximity because of process-flow sequence).