Ultra-High Density, Thin-Film Tantalum Capacitors with Improved Frequency Characteristics for MHz Switching Power Converters

Abstract

High-density passive components are needed for continued miniaturization of complex high-performance electronic systems. Tantalum (Ta) capacitors provide some of the highest volumetric densities achieved due to their combination of high-surface area and relatively high dielectric constant, but suffer from low frequency stability and large form-factors due to the electrode design. In this paper, a printed thin-film tantalum capacitor design is presented. Tantalum capacitor arrays of 1 μF/mm2 up to and beyond 1 MHz. The improved frequency stability comes from the ultra-thin structure of the capacitors, which reduces the path length of the charging and discharging current. The capacitors showed low equivalent series resistance and consistent electrical performance before and after thermal moisture testing at 65°C and 95% relative humidity for 500 h and 1000 h. Due to the ultra-low form-factor, the thin-film Ta capacitor technology can be extended to highly-miniaturized power converters with efficient substrate- or wafer-scale integration.