Influence of moisture on the electrical properties of solution processed multilayer high-k ZrO2-capacitors

Abstract

The dielectric performance of ZrO₂ thin films – which were manufactured by solution deposition of a single-source precursor – strongly depends on the surrounding atmosphere. Capacitors were constructed and impedance measurements were carried out under different environments. The electrical performance under an inert atmosphere in a glove box could be explained with a capacitor and a parallel resistance, whereas the behaviour in ambient air was more complex. Accordingly, further measurements were carried out in a vacuum chamber which allowed flushing with specific components of ambient air. Nitrogen and oxygen did not strongly influence the device characteristics, whereas the presence of water leads to considerable deviations. This effect could also be monitored by X-ray photon spectroscopy which indicated a change in the O 1s peak attributed to surface hydroxylation. Although thicker ZrO₂ films were obtained by repeated deposition of thinner layers, the overall deposit appeared uniform and no evidence of the individual layers could be detected by Scanning Electron Microscopy. The multilayer characteristic of the film only appears by X-ray reflectometry (XRR), revealing a density of 4.4 g cm⁻³, which is only 75% of the density of monoclinic ZrO₂ and must be attributed to porosity within the films. The corruption of the dielectrics in the presence of moisture is thus an effect in the bulk and it is not restricted to the film surface.