Wafer Flow Time Control in Robotized Semiconductor Manufacturing Tools

This research examines the problem of scheduling robotized cluster tools under the operational requirement of controllingwafer flow time. Recently, in wafer fabs, the wafer flow time is recognized as an important factor that impacts the quality level of semiconductor end-products. We first establish a theoretical basis for the analysis of the wafer flow time in cluster tools, and then we prove that the wafer flow time can be significantly reduced by regulating the wafer loading level inside the tool. It is also shown that there is a tradeoff between the wafer flow time and tool productivity, and thus the reduction of the wafer flow time can lead to an increased tool cycle time. To manage this tradeoff effectively, we present a scheduling rule by which the wafer flow time can be effectively controlled while minimizing the productivity loss caused by the increased tool cycle time. The introduced scheduling approach provides practical insights and numerical validation, offering semiconductor manufacturers a viable strategy to enhance both wafer quality and production efficiency.