Preparation of Thin-Film Capacitor with High Reliability by Anodization of Zr–Al Alloy Film

Abstract

We have prepared Zr–Al thin-film capacitors by anodizing a sputter-deposited Zr–Al alloy film with 46 at. % Al, and examined their properties before and after heat treatment and their leakage current mechanism. In addition, anodized Zr–Al films were characterized by X-ray diffraction (XRD) analysis and Auger electron spectroscopy (AES). It is revealed that the reliability of an anodized pure-Zr capacitor is markedly improved by substituting the anodized Zr–Al film for anodized pure-Zr, because the crystallization of anodized Zr–Al amorphous films hardly occurs. In addition, it is clarified that the leakage current mechanism of the anodized Zr–Al capacitor is due to Schottky emission and that the thermal degradation observed after heat treatment above 350 °C is triggered by the diffusion of Zr atoms from the underlying unoxidized alloy layer into the anodized Zr–Al layer.

Dielectric Properties of Zr–Al Anodized Thin Film Capacitors Prepared Using Al-Doped Zr Alloy Films

“…In addition, according to the results of Habazaki et al, 17,18) both Zr and Al atoms in Zr-Al alloy films are uniformly anodized in the system while maintaining the original alloy composition, and a homogeneous mixture of ZrO 2 and Al 2 O 3 is formed. Moreover, we have reported in a previous paper 19) that a Zr-Al(46 at. %) alloy film is uniformly anodized while maintaining its original alloy composition, although the obtained oxide phase is amorphous.…”

“…%) anodized film reported in a previous paper. 19) Thus, we would regard hereafter the Zr-Al(17 at. %) anodized film as the best candidate material for realizing the anodized capacitor of the tetragonal ZrO 2 phase with a high capacitance density.…”

Loss Properties of Anodized Thin-Film Capacitors Fabricated Using Hf-Doped Nb Alloy Films

“…1) These materials can be formed by various preparation methods such as reactive sputtering, 2) pulsed laser deposition, 3) and anodic oxidation. 4,5) Among these preparation methods, it is well known that anodic oxidation is one of the simplest methods for obtaining nearly stoichiometric oxide films. As typical examples, anodized films of Ta and Al have been extensively investigated and practically used as dielectric layers for thin-film electrolytic capacitors.…”