An Enhanced One-Port Waveguide Method for Sheet Resistance Extraction

In this article, a simple and accurate method is proposed to extract the sheet resistance of a thin conductive film by using the enhanced one-port waveguide in a microwave frequency. A shorted quarter-wavelength waveguide is supplemented to the main waveguide as its open boundary to ensure the TE10 mode during the measurement. Unlike the available waveguide with the metal flange, the dielectric flange of the shorted quarter-wavelength waveguide is proposed to eliminate the transverse electromagnatic (TEM) wave propagation and leakage in the gap between two waveguide flanges. The conductive film deposited on the substrate is attached to the main waveguide flange, and the equivalent circuit model is generated thereof. By measuring S11 parameters of the bare substrate and conductive film with the substrate, respectively, the unknown sheet resistance of the conductive film can be easily extracted. Even a large sheet resistance could be measured accurately. Both numerical and measurement results are presented for effectiveness validation of the proposed method. In comparison with the available dual-port method and waveguide with the metal flange method, the dielectric flange raises the measurement accuracy sharply in aspects of substrate thickness, substrate materials, and sheet resistance.