Broadband Permittivity Measurements of High Dielectric Constant Films

Abstract

Our investigation concerns measuring broadband dielectric permittivity and loss tangent of thin film high dielectric constant dielectric materials at microwave frequencies. The measurements are made in an APC-7 coaxial configuration where the test specimen represents a load terminating an air-filled coaxial transmission line. In contrast to conventional lumped capacitance approximations, the parallel plate capacitor filled with a dielectric film is treated as a distributed component consisting of a depressive, transmission line with a capacitance. The model expression for input impedance takes into consideration the wave propagation within the dielectric specimen section and correlates the network parameters with the relative complex permittivity of the specimen. The method is suitable for testing high-k polymer-composite materials having nominal thickness of 1 mum to 300 mum at frequencies of 100 MHz to 12 GHz. With proper calibration and computation the frequency range can be extended to 18 GHz