mm-wave confocal resonators for vertical structure profiling in semiconducting and superconducting materials

The application of the confocal resonator technique to vertical profiling problems for a number of interesting structure types is demonstrated. From the frequency dependence of surface impedance, the vertical conductivity/permittivity profiles are determined for a variety of devices and device materials including implanted Si and GaAs wafers and superconductor-dielectric interfaces. The vertical spatial resolution can be small as several nanometers, and the accuracy of the complex permittivity generally is better than 3%.<>