Systems and Methods for In-Situ Reflectivity Degradation Monitoring of Optical Collectors Used in Extreme Ultraviolet (EUV) Lithography Processes

摘要

Systems and methods for in-situ reflectivity degradation monitoring of optical collectors used in extreme ultraviolet (EUV) lithography processes are described. In one embodiment, a method comprises providing a semiconductor lithography tool employing an EUV source optically coupled to a collector within a vacuum chamber, the collector providing an intermediate focus area, measuring a first signal at the EUV source, measuring a second signal at the intermediate focus area, comparing the first and second signals, and monitoring a reflectivity parameter of the collector based upon the comparison. In another embodiment, a method comprises emitting a signal from a non-EUV light source optically coupled to the collector, measuring a signal reflected by the collector, and monitoring a reflectivity parameter of the collector based upon a comparison between the emitted and measured signals.