Scheduling setup operations for bottleneck facilities in semiconductor manufacturing

This study focused on developing a scheduling heuristic for ion implanter facilities at Cirent Semiconductor (currently Agere Systems) in Orlando, Florida, where implanters facility groups are considered to be a bottleneck. The scheduling heuristic developed in this research aims at balancing workload levels for implanters processing lots at different stages of the wafer production lifecycle. This is accomplished by processing those lots that contribute most to increasing inventory levels at the bottleneck facility. The measures used to evaluate the performance of the proposed heuristic were: mean cycle time, mean work in process (WIP), and standard deviation of cycle time. The performance of the proposed heuristic was compared against the scheduling rules currently in use and against other commonly used dispatching rules using a valid simulation model. Simulation results showed that the heuristic developed in this research performs better than all other rules in terms of mean cycle time and WIP in all cases, and better in terms of standard deviation of cycle time for most cases tested. The heuristic can be used at any bottleneck facility that processes products at different stages of their production cycle and that requires a significant setup time.