Evaluation and Reliability Improvement Investigation of Electrical Characteristics of Ba0.9Sr0.1TiO3 Dielectric Films Prepared by Electrophoretic Deposition Method

Abstract

Ba0.9Sr0.1TiO3 (BST) thin films were deposited by the electrophoretic deposition (EPD) method for an embedded capacitor for printed circuit boards (PCBs). When the dielectric properties were evaluated in air, the leakage current densities were large, from 1×10-2 to 1×10-5 A/cm2 applied at 40 V. On the other hand, when the condition was dry Ar, they greatly decreased to be 5×10-8 A/cm2 at an applied voltage of 40 V. From Fourier-transform infrared (FT-IR) evaluation, the change in dielectric properties caused by changing the measuring atmosphere was attributed to the absorption of moisture in the air. These leakage currents were decreased by coating resin onto the EPD films, even when the measurement was carried out in air. When a resin varnish with 2 wt % concentration was coated onto the film with 1.91 µm thickness annealed at 900 °C for 30 min in N2, the dielectric constant remained almost the same as that of without coating, 221, and the leakage current was 4×10-8 A/cm2 or less at 50 V. The resistance of the resin-coated sample was 10.2 MΩ/cm2 after 1000 h under 85 °C and 85% humidity with a 3.5 V bias.