A Coaxial Probe Fixture Used for Extracting Complex Permittivity of Thin Layers

We have developed a broad-band technique for measuring the complex permittivity (epsiv_r) of dielectric materials, especially thin layers. Our method is based on the use of a coaxial probe. The extraction of the complex permittivity uses a capacitance model valid in a broad frequency range dependent on the sample dimensions and the boundary conditions. Compared to transmission line method, one advantage of the coaxial probe is to avoid the costly lithography process, especially for silicon or SOI substrates. To illustrate our technique, circular samples with a diameter of 2.922 mm are characterised in the range 0.5-25 GHz for a thickness of 0.5mm and various relative permittivity up to 12 with a fixed electric conductivity of 0.2S/m