Imaging nano-defects of metal waveguides using the microwave cavity interference enhancement method

Abstract

Here, we demonstrate a microwave (MW) cavity interference enhancement method to image nano-defects on the surface of metal waveguide. The MW cavity interference system mainly consisted of a MW coaxial resonant cavity with a nano-probe. The MW signals have been evenly divided into two channels. One was the reference signal inputted into the MW waveguide and coupled into the MW cavity via the probe. Also, the coupling strength depends on the distance between the probe and the MW waveguide. Another one was directly inputted the MW cavity to interfere with the reference signal, and was enhanced in the cavity. Then, the surface topography of the metal waveguide was mapped by calculating the enhanced signals. In our experiment, a weak signal of ∼1 pW coupled from the waveguide can be detected by a MW cavity with the quality factor of ∼209. As a proof of application, the topography of nano-defects on the surface of metal waveguide in an MW chip has been mapped with a resolution of ∼15 nm. We have proved that this is a high-resolution, easy-to-manufacture, low-cost, and real-time online monitoring approach for online assessment and screening chips. This potentially has broad applications in the fields of chip manufacturing, chip inspection, nano-structure detection, and so on.