Millimeter-wave permittivity measurement of deposited dielectric films using the spherical open resonator

A differential method using the spherical open resonator is developed for permittivity measurement of a thin dielectric film on an optically dense substrate. It is based on a measurement of the resonant frequency shift due to the thin film on the substrate. The accuracy of the method is demonstrated to be about 4% for a 5.6-μm photoresist film at 142 GHz.