Capacity planning of a photolithography work cell in a wafer manufacturing line

This study was undertaken to help improve the performance of a semiconductor wafer fabrication line. We were concerned with understanding the capacity of the line, how to utilize limited resources to best improve manufacturing performance and to estimate the direction and magnitude of the improvements. The selected performance measure, the cycle time-throughput trade-off curve, aids decision makers to understand the relationship between average cycle time and throughput, enabling them to define the operational capacity of their system to complement the company's manufacturing and marketing goals. With a detailed simulation model of a critical subsystem of a real fabrication line we explore the sensitivity of the trade-off curve to additional resources (operators and equipment), process improvements (reducing setup times and reducing rework) and operational rules (lot sizing and repairman wait time). The approach taken here and many of the qualitative insights gained are not restricted to the setting of a fabrication line and are applicable to many manufacturing environments.