Electrical, structural, and chemical properties of $HfO2$ films formed by electron beam evaporation

High dielectric constant hafnium oxide films were formed by electron beam (e-beam) evaporation on HF last terminated silicon (100) wafers. We report on the influence of low energy argon plasma $(∼70eV)$ and oxygen flow rate on the electrical, chemical, and structural properties of metal-insulator-silicon structures incorporating these e-beam deposited $HfO2$ films. The use of the film-densifying low energy argon plasma during the deposition results in an increase in the equivalent oxide thickness (EOT) values. We employ high resolution transmission electron microscopy (HRTEM), x-ray photoelectron spectroscopy (XPS), and medium energy ion scattering experiments to investigate and understand the mechanisms leading to the EOT increase. We demonstrate very good agreement between the interfacial silicon oxide thicknesses derived independently from XPS and HRTEM measurements. We find that the e-beam evaporation technique enabled us to control the $SiOx$ interfacial layer thickness down to $∼6Å$⁠. Very low leakage current density $(<10−4A/cm2)$ is measured at flatband voltage $+1V$ into accumulation for an estimated EOT of $10.9±0.1Å$⁠. Based on a combined HRTEM and capacitance-voltage $(CV)$ analysis, employing a quantum-mechanical $CV$ fitting procedure, we determine the dielectric constant $(k)$ of $HfO2$ films, and associated interfacial $SiOx$ layers, formed under various processing conditions. The $k$ values are found to be 21.2 for $HfO2$ and 6.3 for the thinnest $(∼6Å)$ $SiOx$ interfacial layer. The cross-wafer variations in the physical and electrical properties of the $HfO2$ films are presented.