Evaluation of Vapor-Plated Oxide Films for Capacitor Dielectrics

Abstract

The development of vapor-plating techniques has made possible the preparation of a variety of oxide dielectric films. The work described in this paper is a preliminary evaluation of the physical and chemical properties of some of these films and their suitability for use as capacitor dielectrics. The physical structure of the films has been investigated by X-ray diffraction techniques. Physical and chemical stability of the films was evaluated by thermal shock tests, resistance to scratch and nature of scratch fractures produced, and a variety of chemical treatments. Optical interferomatic techniques were developed for the accurate measurement of film thickness for determination of dielectric constant, dielectric strength and resistivity. Electrical properties of the films were evaluated by capacitor measurements. Results indicate that vapor plated oxide dielectrics have good potential for capacitor applications. This technique has allowed fabrication of capacitors which show a dissipation factor of less than 1 per cent in the frequency range of 100 cps to 300 kc, a capacitance of more than 100 uuf/mm2, and a time constant of open circuit voltage decay in excess of 1000 seconds. Environmental and accelerated aging tests were carried out on the capacitors and a good correlation with the physical and chemical stability of the films was shown. Other applications for these films are under study.