Reliable PLS Analysis of Etching Solution by Pure Component Selectivity Analysis (PCSA)

Abstract

Pure component selectivity analysis was successfully utilized to enhance the robustness of a partial least squares (PLS) model by examining the selectivity of a given component to other components. The samples used in this study were composed of NH4OH, H2O2 and H2O, a popular etchant solution in the electronic industry. The selective determination of H2O2 without influences from NH4OH and H2O was a key issue since its molecular structure is similar to that of H2O and NH4OH also has a hydroxyl functional group. The best spectral ranges for the determination of NH4OH and H2O2 were found with the use of moving window PLS (MW-PLS) and corresponding selectivities were examined by pure component selectivity analysis (PCSA) based on the comparison between regression vectors from PLS and the net analyte signal (NAS).