Modeling interdigital electrode structures for the dielectric characterization of electroceramic thin films

A combination of physical and numerical modeling has been used to investigate the use of co-planar interdigital electrode (IDE) structures to characterize the dielectric properties of isotropic electroceramic thin films. A periodic two-dimensional IDE structure was simulated by finite-difference numerical modeling to investigate different electrode geometries and film thicknesses. A semi-empirical equation that enables the dielectric properties of the thin film to be calculated from the measured capacitance has been developed and is shown to be consistent with conformal mapping approaches. This equation is shown to agree better with various calculations over a wider range of parameters than the existing equation of Farnell (IEEE Trans. Son. Ultrson., SU-17(3) (1970) 188). Physical simulations of IDE structures with a limited number of electrode fingers have enabled the approach to be generalized to any IDE structure including the important special case of a two-electrode strip-line.