Real-time monitoring of critical AMC compounds in the photolithography cell using a novel laser-based, multi-species detection system

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 laser-based 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.