Response Policies to Process Module Failure in Single-Arm Cluster Tools Subject to Wafer Residency Time Constraints

In semiconductor manufacturing, wafer residency time constraints make the scheduling problem of cluster tools complicated. A process module (PM) in cluster tools is prone to failure. It is crucial to deal with any such failure in a proper and timely manner. If there are feasible periodic schedules in operating a cluster tool before and after a PM failure, it is desired to make it operate continuously when such a failure occurs. However, due to wafer residency time constraints, it is highly challenging to control a tool such that it can be correctly transferred from a feasible schedule before failure to another after it. To solve this problem, a Petri net model is developed to describe the dynamic behavior of a single-arm cluster tool and failure response policies are proposed. The proposed policies are formulated via simple control laws for their easy implementation. Examples are given to show them. Note to Practitioners-For single-arm cluster tools with wafer residency constraints, this work proposes the response policies when a PM fails in wafer fabrication. With a Petri net model, when there are feasible cyclic schedules for both before and after failure, policies are presented to respond to a PM failure such that the wafers in a tool can be completed in a feasible way. The policies require polynomially complex calculation and can be implemented on-line to satisfy the real-time requirements. Therefore, they are applicable to practical semiconductor manufacturing systems.