A modified shifting bottleneck heuristic for minimizing total weighted tardiness in complex job shops

Increases in the demand for integrated circuits have highlighted the importance of meeting customer quality and on-time delivery expectations in the semiconductor industry. A modified shifting bottleneck heuristic is developed for minimizing the total weighted tardiness in a semiconductor wafer fabrication facility. This 'complex' job shop is characterized by re-entrant or re-circulating product flow through a number of different tool groups (one or more machines operating in parallel). These tool groups typically contain batching machines, as well as machines that are subject to sequence-dependent setups. The disjunctive graph of the complex job shop is presented, along with a description of the proposed heuristic. Preliminary results indicate the heuristic's potential for promoting on-time deliveries by semiconductor manufacturers for their customers' orders.