Fourier Transform Infrared spectroscopy (FTIR) using the Attenuated Total Reflection (ATR) method was performed in the mid-IR spectral region on ultrathin ZrO2 films deposited on silicon wafers. A vibrational mode near 710 cm-1 was observed that undergoes a very pronounced absorption line shape change as a function of film thickness. For films that were >54 ? thick, or thinner films that were annealed, a strong absorption band was observed with a peak near ~710 cm-1 with a line width of about ~60 cm-1, and attributed to the tetragonal phase of ZrO2 from our earlier XRD, and XAS studies. For the thinner as-deposited, films (<54 ?), that were studied, this IR line shape feature was much broader, less intense, and slightly shifted to longer wavenumbers. This thickness and thermal treatment dependent behavior was previously reported and attributed to the crystal structural change of ZrO2. The absorption peaks at 710 and 660 cm-1 were attributed to the Eu(LO2) and A2u (LO) modes of tetragonal ZrO2 consistent with theoretical studies. The FTIR-ATR method resulted in the acquisition of absorption spectra with very good signal-to- noise characteristics on ultra thin ZrO2 films where the thickness was as thin as ~30 ? and shows promise as an extremely sensitive and nondestructive tool for high-k dielectric film characterization.
Citation: Journal of Vacuum Science and Technology A
Pub Type: Journals
dielectric films, gate stack, high-K dielectrics, FTIR, Fourier Transform Infrared Spectrometry, zirconium dioxide