Efficient Setup/Dispatching Policies in a Semiconductor Manufacturing Facility

Semiconductor manufacturing performed on expensive machines requires repetitive use of several similar processing operations. Owing to economic considerations, these expensive machines are always shared among many products or a product at different stages of its manufacturing process. The machines require setups between the production of different products or different entries of the same product. Since a product may enter a machine several times for processing, the manufacturing system is often called a re-entrant shop. We consider the problem of reducing mean and variance of the cycle time in semiconductor manufacturing environments. The cycle time of a product (or lot) is usually defined as the time between the release of the product into the manufacturing system and the exit of the product from the system. There are many benefits of reducing the mean cycle time. A small cycle time improves the company's ability to respond to changing customer demands, and reduces the in-process inventory for any given level of throughput. Reducing the variance of the cycle time is also important as it leads to better prediction of the completion time of the product. This in turn facilitates improved coordination of downstream operations on the products such as assembly, etc