Temperature-Programmed Desorption Analyses of Sol–Gel Deposited and Crystallized HfO2 Films

Abstract

Characterizations of sol–gel-derived hafnium dioxide (HfO2) films on silicon (Si) substrates were carried out using X-ray photoelectron spectroscopy (XPS), and temperature-programmed desorption (TPD). Significant water (H2O) desorption and accompanying structural changes in the HfO2 film were observed from the TPD curves. The HfO2 film exhibited two distinct H2O desorption states. One state was due to the desorption of physisorbed H2O and/or chemisorbed Hf–OH saturated in air at the surface area of the HfO2 film. The other state depicted by major peaks was caused by the desorption of H2O which may be produced by the reaction of Hf–OH bonds and/or tightly locked in the micropores between crystal grains in the crystallized bulk HfO2 film (monoclinic crystalline state). For amorphous HfO2 film fired at 450 °C, the major peak of the TPD curve was symmetrical, indicating that H2O was detected as a result of the reaction of Hf–OH bonds, which is reaction-controlled (the second-order reaction), whereas at 550 and 700 °C (monoclinic), the major peak of the TPD curve was nonsymmetrical (diffusion-controlled; the first-order reaction). On the basis of the capacitance–voltage (C–V) characteristics, the dielectric constant (permittivity εHfO2 ) of the sol–gel-derived HfO2 film was calculated to be 19, which compares well to those reported for HfO2 prepared by chemical vapor deposition (CVD) and physical vapor deposition (PVD).