Ultra-Thin Zirconium Oxide Films Deposited by Rapid Thermal Chemical Vapor Deposition (RT-CVD) as Alternative Gate Dielectric

Abstract

ZrO₂ ([.kappa]∼ 18) was deposited on Si(100) wafers by rapid thermal chemical vapor deposition (RT-CVD) process to replace SiO₂ as the gate dielectric material in metal-oxide- semiconductor devices for its high dielectric constant, good thermal stability on silicon, and large bandgap. The deposited films are nearly stoichiometric, amorphous, uniform, and highly smooth, as determined by X-ray photoemission spectroscopy, X-ray diffraction, ellipsometry, and atomic force microscopy. The high resolution transmission electron microscopy (TEM) image shows an interfacial ZrSiO₄ layer between ZrO₂ and the silicon substrate, and this interfacial layer is verified by thermodynamic calculations and etching resistance measured at the interface. Excellent step coverage was observed for depositing ZrO₂ on nanometer scale features with an aspect ratio of 4. The dielectric constant of RTCVD ZrO₂ was 15-18, with small C-V hysteresis and low leakage current.