Physicochemical Analysis of Nanoscale Metal Oxide Thin Film Precursors via Infrared Spectroscopic Ellipsometry

We present a nondestructiveand highly sensitive experimental methodologyfor accurately controlling the chemical pathways of metal oxide formationin ultrathin films (& SIM;10 nm) relevant for electronic devices,such as thin film transistors. Utilizing infrared spectroscopic ellipsometry(IRSE), we shed light on the individual sol-gel precursor conversionstages of In(NO3)(3) and Zn(CH3COO)(2) films into In2O3 and ZnO via a thermallyinduced reaction. Employing IR highly reflective substrates (TiN,Al, and Au), the intrinsic sensitivity of IRSE is enhanced; we presentthe chemical signatures of precursor byproducts, which are detecteddown to nanometer-scale thin films. We provide insights into the linkbetween the chemical conversion, the substrate's reflectivity,and IRSE sensitivity and propose a universal methodology for accuratephysicochemical analysis of ultrathin films.