Numerical Study of the Electrical Properties of Insulating Thin Films Deposited on a Conductive Substrate

Parametric finite element simulations were performed to study the effect of film thickness, and electrode size on the different impedance parameters for insulating thin films deposited on a conductive substrate. COMSOL Multiphysics was used to solve the quasi-static form of Maxwell’s electromagnetic equations in time harmonic mode. Several types of 2D models (linear and axisymmetric) were considered. The full model dealt with a configuration in which the impedance is measured between two electrodes deposited on top of the films. The simplified models consisted of a top and a bottom electrode, while ignoring the substrate. By comparing the full model and the simplified models, approximations and generalizations were made. It was found that for highly insulating films, even simplified models can provide accurate capacitance values. However, the edge effects on the capacitance are found to be significant as the film thickness is increased or the electrode contact size is decreased.