Determining operating criterion of batch processing operations for wafer fabrication

All semiconductor manufacturing systems involve batch processing operations. These operations can have a significant impact on product cycle times. Semiconductor manufacturers are often interested in batch processing policies that minimize the sum of the weighted cycle time of all products, where the weights indicate the priority levels of products. A well-known minimum batch size (MBS) policy is generally recognized as an effective policy. However, there is no guideline in determining the minimum batch sizes to start batch processing operations for this policy. This paper illustrates the use of an analytical queuing model to determine these minimum batch sizes. Illustrations of the effectiveness of the approach are provided through a comparison simulation study of various batch processing policies of a real-world semiconductor manufacturer with multiple products and with small to medium volumes. The comparison results suggest that using an analytical queuing model to determine batch sizes for the MBS policy gives a better minimum sum of the weighted cycle time of all products than the other policies considered.