Having established detection limits for transition elements exceeding current requirements of the semiconductor industry, our recent efforts at the Stanford Synchrotron Radiation Laboratory (SSRL) have focused on the improvement of the detection sensitivity for light elements such as Al. Data analysis is particularly challenging for Al, due to the presence of the neighboring Si signal from the substrate. Detection limits can be significantly improved by tuning the excitation energy below the Si-K absorption edge. For conventional TXRF systems this can be done by using a W-Mα fluorescence line (1.78 keV) for excitation.At a synchrotron radiation facility energy tunability is available. However, in both cases this results in a substantial increase in background due to resonant x-ray Raman scattering. This scattering dominates the background under the Al Kα fluorescence line, and consequently limits the achievable sensitivity for the detection of Al surface contaminants. In particular, we find that for a precise determination of the achievable sensitivity, the specific shape of the continuous Raman background must be taken into account in the data analysis. The data deconvolution presented here opens a new perspective for conventional TXRF systems to mitigate this background limitation. This results in a minimum detection limit of 2.4 x 10 9 atoms /cm 2 for Al. 1Based on these results it will also be demonstrated that by improving the detector resolution, the minimum detection limit can be improved significantly. For a detector resolution of 15 eV as predicted for novel superconducting tunnel junction detectors, an improvement in minimum detection limit of about a factor of 3 can be estimated. Keywords:Total reflection X-ray fluorescence, low Z elements, Stanford Synchrotron Radiation Laboratory IntroductionExploiting the unique capabilities of synchrotron radiation, total reflection x-ray fluorescence spectroscopy (TXRF) has been successfully applied to detect very low concentrations of impurities on Si wafer surfaces [1,2,3,4]. Synchrotron radiation offers several advantages over conventional x-ray tubes: It provides a high incident flux, especially from insertion devices, it is both low-divergence and linearly polarized, which leads to an increased fluorescence signal while reducing the elastically scattered background. In addition, tuning the x-ray energy to a characteristic absorption threshold of a typical element present in the wafer surface increases the excitation cross-section for this element which leads to higher fluorescence intensities. With these combined capabilities we routinely achieve an minimum detection limit of < 9 x 10 7 atoms/cm 2 for transition metals on Si wafer surfaces for a 1000 second spectrum.On the other hand, the detection of low Z elements such as Al is challenging because of the lower fluorescence yield as compared to transition metals. In addition, the detection of Al on Si wafers is difficult because of the presence of the much stronger Si substrate signal which tends to dominat...