ExPro—An Expert System Based Process Management System

This paper reports the design, development and preliminary testing of ExPro, an expert system based process management system. This system is designed to provide process setup, monitoring, and supervisory control capabilities for applications in a real-time semiconductor manufacturing environment. ExPro is a rule-based system developed using the OPS-83 expert system language in a personal computer environment. It features a modular structure and includes an integrated analytical process simulator. The simulator is used to predict process parameters prior to processing. It is also used to provide wafer state information from real-time (measured) process information when direct measurement of the state is impractical. The specific process selected for development and demonstration purposes was rapid thermal oxidation (RTO), a technique used in the controlled formation of thin silicon dioxide layers for silicon integrated circuits. This is an appropriate testbed for ExPro as direct process variable feedback may be obtained in real-time from the equipment but wafer state may not. Testing revealed that the accuracy of the system was within 1% of goal for the case of (100) wafers but the less accurate (111) simulation led to much larger errors.