Optimized Miniature Thin-Film Planar Inductors, Compatible with Integrated Circuits

Abstract

The theoretical background and techniques for constructing multipurpose miniature thin-film inductors are presented. These inductors use a thin-film gold spiral encapsulated with deposited ferrite film and present Q values of 100 in the range of 1-1200 µH. The ferrite film is deposited from thermal decomposition of an iodine solution containing the desired metal cations. The magnetic and electric properties of the deposited ferrite films are presented. A technique for etching the gold conducting spiral is described. The geometric form of the conducting spiral is optimized to give the minimum power dissipation. Skin-effect losses, eddy-current losses, hysteresis losses, and the total dissipation factor of the inductors are derived theoretically and compared with the experimental results. The frequency, current, and temperature characteristics of the thin-film planar inductors are fully described.