Improving diffusion furnace capability using model-based temperature control in a production environment

This paper describes the design, development, and implementation of model-based temperature control (MBTC) to improve diffusion furnace capability in a production environment. An integrated manufacturable approach for modeling and robust H_∞ multivariable controller design is developed to replace standard proportional integral derivative (PID) furnace control. The design was originally evaluated on an oxidation furnace and is presently being propagated throughout the entire diffusion area. Production results demonstrate excellent temperature control, tighter process results, and increased utilization. Manually induced disturbances during ironman testing, as well as normal production disturbances, have shown the system requires no adjustment or reconfiguration for improved control of oxidation growth and LPCVD film deposition