High-Dielectric-Constant PLZT Films on Metal Foils for Embedded Passives

Abstract

Ceramic film capacitors with high dielectric constant and high breakdown strength would result in advanced power electronic devices with higher performance, improved reliability, and enhanced volumetric and gravimetric efficiencies. We have grown ferroelectric films of lead lanthanum zirconate titanate (PLZT) on base metal foils by chemical solution deposition. Their dielectric properties were characterized over the temperature range between −50 and 150°C. We measured a dielectric constant of ≈700 and dielectric loss of ≈0.07 at −50°C and a dielectric constant of ≈2200 and dielectric loss of ≈0.06 at 150°C. At room temperature, we measured a leakage current density of ≈6.6 × 10−9 A/cm2, mean breakdown strength of 2.6 MV/cm, and energy density >85 J/cm3. A series of highly accelerated lifetime tests (HALT) was performed to determine the reliability of these PLZT film-on-foil capacitors under high temperature and high field stress conditions. Samples were exposed to temperatures ranging from 100 to 150°C and electric fields ranging from 8.7 × 105 V/cm to 1.3 × 106 V/cm during the HALT testing. Breakdown behavior of the samples was evaluated by Weibull analysis. The mean time to failure was projected to be >3000 h at 100°C with a dc electric field of ≈2.6 × 105 V/cm.