Characterization of Phosphosilicate Thin Films Using Confocal Raman Microscopy

We have demonstrated a characterization tool based on confocal Raman microscopy capable of studying the vibrational spectrum of silica-on-silicon-based thin films within a confined, ~1 micron sup 3-size volume beneath the sample surface. The Raman spectra of a set of phosphosilicate thin film samples have been quantitatively analyzed and correlated with both phosphorus concentration Cp and refractive index n, as determined by conventional methods. The normalized intensity of the P=O vibration scaled linearly with Cp and n, and allowed for the calibration of the Raman measurements to a precision of ~0.2 wt.%P and ~10 sup (-4) in index. The capability of this technique for studying index and dopant profiles in arbitrary systems is also discussed.