Scheduling of single-arm cluster tools with multi-type wafers and shared PMs

As the wafer size increases and consumption demand changes, wafer fabrication mode tends to be multi-type and small-batch production. However, most of existing scheduling methods focus on the control problems of single wafer type, which is not suitable for the scheduling of multiple wafer types. With wafer residency time constraints considered, this paper concentrates on the scheduling and control problems of single-armed cluster tools with multi-type wafers and shared PMs. To balance workloads among processing steps, a virtual processing modules technology is adopted. According to the modified backward scheduling strategy, analytic expressions for testing schedulabilities are derived. Finally, a periodic scheduling algorithm for steady-state is presented. Meanwhile, illustrative examples are given to verify the feasibility and availability of the proposed algorithm.