Heuristic Scheduling of Serial-Batch Processor System for Cycle Time Reduction

Control of batch processors is one of the most important issues in semiconductor manufacturing. Ineffective dispatching policies may cause an increase in overall cycle time. This paper presents a real-time scheduling heuristic for a production unit consisting of a serial processor feeding a batch processor. In this multiple product batching problem, our objective is to reduce the average waiting time in the batch processor’s queue. Our automated policy uses downstream information to schedule the next lot in the serial processor when the batch processor is busy. When the batch processor is idle, it uses upstream information to decide whether to start the batch process or wait for another arrival of any type existing in the serial processor’s buffer. The problem setting allows the selection of the next arriving lot type to the batch processor out of available types at the serial processor to reduce the average cycle time. Simulation is used to benchmark our approach with other policies. Results show that using upstream and downstream information reduces waiting times in the batch queue.