Direct monitoring of semiconductor wafer cleaning solutions using attenuated total reflection far ultraviolet spectroscopy

Far-ultraviolet (FUV) spectroscopy combined with attenuated total reflection (ATR) is employed for direct measurement of the concentrations of semiconductor wafer cleaning fluids such as SC-1 and SC-2. FUV absorption spectra of these aqueous solutions in the 170 – 200 nm region are highly sensitive to changes in both hydrogen bonding and hydration. We adopt quartz as an internal reflection element (IRE) for ATR measurement. We created calibration models for predicting both NH3 and H2O2 in the concentration ranges of 1 – 10 % in SC-1 using multiple linear regression (MLR). The standard deviations of the models were 0.033 % and 0.265 % for NH3 and H2O2, respectively. The same procedure was repeated under the same conditions for HCl and H2O2 in SC-2, yielding corresponding values of 0.018 % for HCl and 0.178 % for H2O2.