Scheduling of single-arm cluster tools mixedly processing two kinds of wafers

This paper studies the scheduling problem of single-arm cluster tools that mixedly process two different kinds of wafers without sharing and revisiting processing modules (PMs). We balance internal workloads by adjusting the number of PMs used to process wafers, and balance the external workloads by configuring virtual PMs. We derive the scheduling conditions for single-arm cluster tools, which are more relaxed than the existing ones. We can also use less PMs to get the same production cycle time as the existing literature using configuration of virtual PMs only. We give some examples to show the application and power of the theory.