Fuzzy-logic tools on tap for IC wafers

The authors briefly describe the concept of fuzzy logic, and develop a technique for detecting dimple defects for automatic visual inspection of polished wafer surfaces. A fuzzy logic controller balances a beam in real-time without an explicit closed-form mathematical formulation. This in-house prototype can be operated automatically through the execution of a fuzzy control algorithm. Unlike most of the conventional and optimal control algorithms, this controller requires no system dynamics, and it is characterized by its simplicity and easy implementation. It is a convenient tool for automating operator controlled processes, although theoretical results concerning the system´s stability and robustness are still not available and cannot be easily obtained.<>