There is widespread recognition in the industry that as the design rule decreases, the number of airborne molecular compounds that can drive defect formation is increasing at an exponential rate [citation: IRDS 2020]. The vast majority of these new critically important AMCs are volatile organic compounds. These VOCs are difficult to measure in the gas phase at the parts-per-billion and parts-per-trillion levels that are needed for the tight process control requirements of advanced design rules. In this paper, we report on a novel AMC chemical metrology solution for measuring critical VOCs that are relevant to the photolithography cell. The heart of the system is a real-time laserbased analyzer based on a new analytical technique called Broad Band Cavity Ring Down Spectroscopy (BB-CRDS). The VOC monitoring system has several features which make it ideally suited to AMC measurements in the production environment: ultra-trace measurements at ppb levels without the need for calibration, 24/7 operation without user intervention, and negligible consumables. The analyzer was integrated into a state-of-the-art multiplexer to monitor ten VOC species in the photolithography cell in a modern semiconductor fab. We report on multiple observations made, including transient solvent leak events, multifunction chemical filter performance, and baseline characterization of AMCs inside track tools.
|