An Analysis of Semiconductor Reticle Management Using Discrete Event Simulation
P.J. Byrne
Summer Computer Simulation Conference 2007 (SCSC 2007)
San Diego, California (USA), July 15-18, 2007
Abstract
Semiconductor manufacturing is complex, with photolithography generally being regarded as its most constraining area. Within photolithography, reticles and reticle management in a multi-product, multi-machine environment is critical to the efficient operation of the entire fab. Product specific reticles are required to be on a tool to run each product and products change continuously from batch to batch. Having too few reticles can lead to under utilisation of tools and increased cycle time, whereas having too many reticles is extremely expensive. In the case studied, two different types of steppers exist; one set uses 5 inch reticles with the second set using 6 inch reticles. The question in this instance is what proportion of reticles should be purchased as 5 inch, 6 inch or both taking into account system constraints. Discrete event simulation has been used to model this complex system. These models are then populated with industrial data and used for decision support with respect to reticle acquisition for the next planning period. Tool utilisation and average wait times are used to measure the effectiveness of different reticle purchase plans.