Test head scheduling in a semiconductor test facility

It is well recognized that "Testing" is one of the critical activities in the final manufacturing of semiconductor devices that includes probe and assembly operations. The manufacturing environment at the "Testing" stage is characterized by multiple products, test equipment with varying capability, and specialized kits and handlers that may be product and equipment specific. Together these features lead to a complex scheduling problem that is difficult to solve. Current practices for scheduling in this environment are inadequate and result in a degradation of system performance leading to lower utilization, poor on-time delivery and high work-in-process inventories. In this paper we describe the development, validation and implementation of a decision support system to address the scheduling issues in the Testing facility. Using a platform of commercially available factory planning software, we develop a scheduling model and a heuristic based solution approach for the test facility. The goal of the Test Head Scheduler is to maximize the due-date performance while improving the throughput of-the test facility within the material and capacity constraints. The primary outputs of the system include schedules for device testing, resource profiles for handlers, kits and equipment and due date performance reports. The data for the model comes from customer-order databases, equipment maintenance records, real-time equipment inventory and shop floor control systems. Preliminary validation of the model is based oil inputs from production schedulers. The final version and testing of the algorithms is based on real life data from the shop floor. The model is generic enough to schedule an engineering pilot line as well as full production environment both of which ate part of a large semiconducto-manufacturing organization.