RAMAN SENSOR FOR SUPERCRITICAL FLUIDS METROLOGY

An apparatus includes a measurement chamber configured to retain one or more sample substances. The apparatus includes an entrance window mounted on a side of the measurement chamber. The apparatus includes a light source configured to generate an incident light beam. The apparatus includes a Raman sensor configured to collect inelastically scattered light from the chamber, and measure an intensity of a Raman peak of a first substance from the one or more sample substances based on the collected inelastically scattered light. The apparatus further includes a processor configured to (i) calculate a concentration of the first substance based on at least the measured intensity of the Raman peak of the first substance, (ii) determine the end point of a wafer cleaning process based on a calculated concentration of the first substance, and (iii) terminate the wafer cleaning process based on the determined end point.