Quantification of substitutional and interstitial carbon in thin SiGeC films using in-line X-ray-photoelectron spectroscopy
Résumé
One of the most important questions concerning the epitaxial growth of Si1-yCy or Si1-x-yGexCy is the ratio of carbon incorporated into substitutional and interstitial sites, which is highly dependent on growth conditions. Usually, the quantification of the total (Ctot), the substitutional (Csub) and the interstitial (Cint) carbon concentrations is achieved using a combination of secondary-ion mass spectrometry and X-ray-diffraction, based on careful calibration and appropriate preparation. In this study, we demonstrate the potential of non-destructive, in-line X-ray photoelectron spectroscopy to obtain the quantification of both Csub and Cint in a single measurement. For substitutional carbon atoms, the XPS C 1s signal intensity increases proportionally with the carbon content, with a characteristic peak at 284.00 eV. When carbon is incorporated into interstitial sites, a shift of the C 1s peak towards lower binding energies is detected. Moreover, a broadening of the peak is observed, due to the appearance of a characteristic peak at 283.30 eV. Here, we describe the development of a measurement procedure and provide a critical discussion on the possible sources of error. Finally, an excellent correlation between the newly developed XPS quantification and the standard XRD/SIMS method is demonstrated.
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