Local microwave characterization of metal films using a scanning microwave near-field microscope

In microwave integrated circuits, the performance of devices is often influenced by the homogeneity of microwave properties of metal thin films in the circuits. In this paper, a scanning microwave near-field microscope (SMNFM) has been designed using a coaxial resonator as the probe, to study the local microwave properties of the electronic devices. Several typical samples of metal films have been measured and the results have shown that we can image the local microwave properties by recording the changes of the resonant frequency and quality factor of the coaxial resonator probe. The spatial resolution of the SMNFM has been improved to be better than 5 μm by utilizing a probe with a structure similar to that used in a scanning tunnelling microscope. To demonstrate the ability of local microwave characterization, the surface resistances of Cr thin film and Ag/Cr multilayer have been imaged by the SMNFM.