Scheduling of time constrained dual-arm cluster tools with wafer revisiting

This work intends to schedule a dual-arm cluster tool for the atomic layer deposition (ALD) process with wafer residency time constraints. ALD is a typical wafer revisiting process. Based on the analysis of system properties, a novel scheduling strategy called modified 1-wafer cyclic scheduling is derived. With this strategy, necessary and sufficient schedulability conditions are established. If schedulable, scheduling algorithms are presented to obtain a feasible and optimal schedule. By the proposed method, a schedule can be found by just simple calculation. An illustrative example is given to show the application of the proposed approach.