Electrode Defects in Multilayer Capacitors Part II: Finite Element Analysis of Local Field Enhancement and Leakage Current in Three‐Dimensional Microstructures

Abstract

Multilayer ceramic capacitors (MLCCs), owing to their processing conditions, can exhibit microstructure defects, such as electrode porosity and roughness. The effect of such extrinsic defects on the electrical performance of these devices needs to be understood to achieve successful miniaturization. To understand the influence of microstructural defects on field distributions and leakage current, the three‐dimensional (3‐D) microstructure of a local region in MLCCs is reconstructed using a serial‐sectioning technique in the focused ion beam. This microstructure is then converted into a finite element model to simulate the perturbations in electric field due to the presence of electrode defects. The electric field is significantly enhanced in the vicinity of such defects, and this is expected to have a bearing on the leakage current density of these devices. To simulate the scaling effects, the dielectric layer thickness is reduced in the 3‐D microstructure keeping the same electrode morphology. It is seen that the effect of microstructure defects is more pronounced as one approaches thinner layers, leading to higher local electric field concentrations and a concomitant drop in insulation resistance.

Electrode Defects in Multilayer Capacitors Part I: Modeling the Effect of Electrode Roughness and Porosity on Electric Field Enhancement and Leakage Current

“…34 As observed in the VC-SEM images, local perturbations in electric potential take place due the presence of these electrode defects, as predicted by the finite element modeling.…”

Effect of Firing Rates on Electrode Morphology and Electrical Properties of Multilayer Ceramic Capacitors

“…Thus, the high‐local electric field places severe limitations on device performance due to enhanced local leakage current, and therefore reduces the operating voltage of the devices. As discussed in a prior study, the effect of electrode defects are magnified as one approaches submicrometer dielectric layers, and therefore compromises the advancement toward higher volumetric capacitance through miniaturization . Under such conditions, it becomes extremely important to have smoother and more continuous electrodes in state‐of‐the art MLCCs.…”

“…These volumes are then used as a model to simulate electric field distribution in the dielectric layer by finite‐element modeling in and around the electrode region using the finite‐element solver COMSOL. The complete details of the 3‐D visualization and simulation technique are discussed elsewhere . .…”

“…demonstrated the dependence of leakage current on the metal–insulator interface morphology due to local electric field enhancements around roughness . In the past, some of these observations have been quantified by calculating the electric field distribution in the presence of electrode defects such as porosities and roughness . Both analytical and numerical approaches have revealed defects such as the sites of high‐local electric fields, which in turn gave rise to higher leakage currents.…”

“…7,14 In the past, some of these observations have been quantified by calculating the electric field distribution in the presence of electrode defects such as porosities and roughness. 15,16 Both analytical and numerical approaches have revealed defects such as the sites of high-local electric fields, which in turn gave rise to higher leakage currents. Levi et al demonstrated that even the presence of grain-boundary grooving in a Ni electrode could lead to an enhanced electric field, and thus, could reduce the interface resistance in those regions.…”