Effects of particle size on dielectric constant and leakage current of epoxy/barium titanate (BaTiO3) composite films for embedded capacitors

Polymer/ceramic composite film is of great interest as dielectric material for embedded capacitor applications. In this paper, effects of powder size on dielectric constant and leakage current of epoxy/BaTiO ₃ composite film fabricated by spin-coating were investigated using bisphenol-A type epoxy and 6 kinds of barium titanate powders with diameter ranges of 0.1-0.9 μm. Dielectric constant of the composite films increased as particle size increased. This was due to tetragonality increase, which was observed by XRD analysis, with particle size increase. In addition to tetragonality, better dispersibility also contributed to high dielectric constant of bigger powder. Leakage current of composite films increased dramatically as particle size increased. It is presumably due to the decrease of the number of particles per unit length, resulting in decrease of the number of contacts. As the number of contacts acting as a potential barrier reduces, potential barrier lowering effects become larger. When we use larger powder, we can obtain higher dielectric constant with larger leakage current. As a result, there is tradeoff between high dielectric constant and low leakage current, and 0.5~0.7 μm size powder would be optimum for embedded capacitor applications