Submicron X7R dielectric materials

The rapid growth in the multilayer capacitor (MLC) market is linked to the growth in its use in integrated circuits. As the drive towards higher density packaging continues MLCs also have to develop higher volumetric efficiencies of capacitance, good high frequency performance, higher reliability, and maintain a relatively low cost. Certain temperature stabilities of capacitance are necessary as the capacitor often works in a range of temperatures. The X7R specification requires a capacitance change less than +/-15% over the temperature range of -50 degrees C to 125 degrees C. In this work ceramic X7R dielectrics were developed based on a hydrothermal BaTiO3 powder. The fine grain size enables the fabrication of thinner dielectric layers, and the high dielectric constant of the material promotes a higher volumetric efficiency of capacitance. The relatively low sintering temperature of the material also allows the use of less expensive Ag/Pd internal electrodes. The X7R materials have a unique core-shell microstructure as the result of an engineered chemical micro-inhomogeneity. The effects of the dopants and sintering control on the formation and evolution of the core-shell structure along with the microstructure-dielectric behavior relationship in these submicron grains were investigated through Transmission Electron Microscopy (TEM) and measurement of dielectric properties.