Chemical metrology: a novel approach to measuring critical airborne molecular contamination in photolithography and track tools in real time

Airborne chemical contaminants (AMCs) in the lithography cell are responsible for yield-impacting issues such as scanner haze and wafer defects. Detecting and monitoring these chemicals in real-time is critical in IC fabs. Many technologies have been deployed to monitor AMCs, but many of them are not production-worthy solutions that meet the stringent sensitivity and throughput requirements driving Moore's law. Here, we demonstrate a fully integrated AMC monitoring system, Picarro SAM (Sample. Analyze. Monitor.), that detects a variety of chemicals in real-time from multiple locations in a lithography cell. Multiple scanners, track tools, and reticle stockers are monitored 24X7 for excursions of critical inorganic AMCs such as hydrochloric acid, hydrofluoric acid, ammonia, and sulfur dioxide, as well as volatile organic compounds such as acetic acid, PGMEA, NMP, siloxanes, etc. that impact the performance of the lithography process. The SAM system integrates sensors based on Cavity Ring-Down Spectroscopy (CRDS) with a high-performance sampling system. While CRDS is an established technology to detect critical inorganic AMCs, here we demonstrate the ability to measure several critical VOCs using a new technique called broadband CRDS. SAM monitors contaminants in various parts of the scanner and track with multiple sampling tubes extending to a hundred feet or more to accommodate remote areas of the process tool. The SAM system is a fast, easy-to-use, production-ready analytical tool to monitor trace VOC and inorganic contaminants in the parts per trillion to low ppb range within seconds that helps engineers take corrective actions much faster than ever before.