Effects of the reaction parameters on the deposition characteristics in ZrO₂ CVD

Abstract

Zirconium dioxide (ZrO₂) films have been deposited on to silicon wafers by the chemical vapour deposition (CVD) technique involving the application of gas mixtures of ZrCl₄, CO₂, and H₂. The relationships between the deposition rate and various reaction parameters, such as the gas flow rate, the deposition temperature, and the composition of reactant gases, were studied. The film was identified as nearly stoichiometric monoclinic ZrO₂ by using X-ray photoelectron spectroscopy, infrared transmission, and X-ray diffraction. Zirconium tetrachloride (ZrCl₄) is the only species acting as zirconium donor which results from thermodynamic calculations in the present system. The CVD of ZrO₂ is a thermally activated process and the activation energy is about 80 kJ mol⁻¹ at the surface chemical reaction controlled region. The deposition mechanism, initially a kinetic process controlled by diffusive mass transfer, becomes a kinetic process governed by the surface chemical reactions with increasing total flow rate above 700°C. The dependence of the deposition rate on the reactant gas composition is mainly affected by the relative contents of the zirconium donor and the oxygen donor. At ZrCl₄ mole fractions lower than 2.0 × 10⁻³, the deposition rate increases with the ZrCl₄ mole fraction; however, at ZrCl₄ mole fractions higher than that the deposition rate is mainly influenced by the H₂O-forming reaction between CO₂ and H₂.