Production scheduling in a semiconductor wafer fabrication facility producing multiple product types with distinct due dates

This paper focuses on production scheduling in a semiconductor wafer fab producing multiple product types that have different due dates and different process flows. In the wafer fab, wafer lots are processed on serial and batch processing workstations, each of which consists of parallel identical machines. Machines in serial processing workstations process wafer lots one by one, while those in batch processing workstations process several wafer lots of the same recipe at the same time. What need to be done for production scheduling are lot release control (to determine when and which wafer lot to release into the wafer fab), lot scheduling (to determine processing sequences of lots waiting in front of serial processing workstations) and batch scheduling (to determine which lots to process simultaneously as a batch and when to process batches on batch processing workstations). For these three decision problems, we develop several rules which use information such as order sizes (numbers of lots in orders) and processing status of the wafer lots. To evaluate these new rules, we use a simulation model in which the three decision problems are considered simultaneously. Simulation results show that the new rules work better than existing rules in terms of total tardiness of the orders.