Tractable nonlinear production planning models for semiconductor wafer fabrication facilities

We describe a simulation study of a production planning model for multistage production inventory systems that reflects the nonlinear relationship between resource utilization and lead time. The model is based on the use of clearing functions that capture the nonlinear relationship between workload and throughput. We show how these clearing functions can be estimated from empirical data using a simulation model as a surrogate for observation of the production system under study. We then examine the sensitivity of the estimated clearing function to different dispatching algorithms, different demand patterns, and production planning techniques. Computational experiments based on a scaled-down model of a semiconductor wafer fabrication facility illustrate the potential benefits of the clearing function model relative to conventional linear programming models.