Real-time HCl gas detection at parts-per-billion level concentrations utilising a diode laser and a bismuth-doped fibre amplifier

HCl measurements in a cleanroom environment are carried out using a cavity ring-down analyser in order to get an estimate of the HCl concentrations that can be expected to be present in semiconductor manufacturing. HCl is a reactive gas and the materials used for gas sampling and transportation have a significant effect on the measurement response time; hence, data on HCl adsorption to different materials is also provided. Finally, a light source operating at 1742 nm that can be used for HCl detection in a multi-gas analyser based on multipass photo-acoustic spectroscopy is presented. Preliminary results indicate that sub-ppb detection levels are achievable using this approach even for HCl.