Simple and reliable Raman measurement of an etchant solution directly through Teflon tubing

Abstract

A semiconductor etchant solution was analyzed using wide area illumination (WAI) through Teflon tubing. A diluted sulfuric acid/hydrogen peroxide (DSP) solution, composed of hydrogen peroxide and sulfuric acid in water, was selected and Raman spectra were collected using the WAI scheme. The concentration of each component was determined by generating random numbers to minimize correlations among them. Principal component regression was utilized to determine H2O2 and H2SO4 concentrations. The calibration models were developed using the calibration set, and its prediction performance was evaluated by predicting spectra in the validation set. Raman bands of H2SO4 were observed at 1050, 980, and 895 cm-1. Results show that these bands correspond to the vibration of acid sulfate, and the intensities of these peaks increases with respect to increased concentration.