Attenuated total reflection fourier transform infrared spectroscopy (FTIR ATR) was performed on ultrathin ZrO2 films as thin as approximate to 3.0 nm deposited on silicon. An observed vibrational mode near 710 cm(-1) undergoes a very pronounced absorption line shape change, corresponding to a structural phase change, as a function of film thickness and thermal processing. This absorption, attributed to the E-u(LO2) and A2(u)(LO) modes of tetragonal ZrO2, marks the first experimental measurement and verification of vibrational modes for tetragonal ZrO2 in this spectral range. The FTIR-ATR method shows promise as an extremely sensitive and nondestructive tool for high-kappa dielectric film characterization. (C) 2008 American Vacuum Society.