Distributed control systems in automated IC manufacturing

The authors describe the use of direct digital control systems at the diffusion furnace level and cell-level supervisory systems for the collection and analysis of production data. The application of integrated computer control to the manufacture of advanced ICs is shown to have a measurable impact on device parameters, wafer throughput, repeatability, and product quality. A representative example based on the evaluation of device current gain uniformity resulting from conventional control technologies is compared to the results obtained in a digitally controlled furnace. The authors discuss a system architecture consisting of microprocessor-based furnace controllers plus a powerful cell controller which handles many error-prone functions in the manufacturing process. Finally, some future trends in the further development of such systems are discussed