Raman sensor for supercritical fluids metrology

An apparatus for in-situ cleaning end point detection, the apparatus comprising:

• a measurement chamber configured to retain one or more sample substances;
• an entrance window mounted on a side of the measurement chamber;
• a light source configured to generate an incident light beam, the incident light beam being directed through the entrance window into the chamber, the incident light beam being inelastically scattered inside the chamber by the one or more sample sub stances;
• a Raman sensor configured to collect the 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;
• and
• a processor configured to (i) calculate a concentration of the first substance from the one or more sample substances 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.