Causes of high leakage currents in thin BaTiO3 films prepared by aerosol deposition method

To achieve a high capacitance density for embedded planar decoupling capacitors, we grew BaTiO3 thin films on Cu substrates at room temperature by using an aerosol deposition method, and we examined thickness dependence of their electrical properties. When the thickness of the films was below 1 μm, their leakage currents abruptly increased, indicating short circuits, compared with those of thicker ones. Through an observation of their surface morphologies associated with variations in the film thickness, we confirmed that defects, such as pores, craters, and not-fully-crushed particles, in the films with thickness below 1 μm brought about high leakage currents and that they were generated by large or agglomerated particles in the source powder. In addition, simulations were conducted by using a finite element method to investigate the influence of the electric field intensity on the leakage currents due to the uneven surfaces on the films and the interfaces between the films and the Cu substrates. We conclude that reduced roughness is crucially important in preparing thinner films for further increasing the capacitance density.