A Systematic Procedure for Evaluating the Achievability of an Output Time Forecast in a Wafer Fab

Lot output time prediction is a critical task to a wafer fab (fabrication plant). Traditional studies are focused on prediction accuracy and efficiency. Another performance measure that is as important but has been ignored is the achievability of an output time forecast, which is defined as the possibility that the fabrication on the wafer lot can be finished in time before the output time forecast. In this paper, a systematic procedure is proposed to predict the output time of a wafer lot and to evaluate the achievability of the output time forecast. The systematic procedure is composed of two parts: a BPN and a set of fuzzy inference rules. With the proposed methodology, both output time prediction and achievability evaluation can be concurrently accomplished. Key-Words: Output time prediction; Back propagation network; Fuzzy inference rules; Achievability; Wafer fab