Transmission microwave spectroscopy for local characterization of dielectric materials

In this work, the authors present a technique for the local characterization of the dielectric properties of materials. More in details, a setup will be described, and the related measurement modeling will be discussed. In this way, it is possible to obtain a calibrated and nondestructive determination of the dielectric constant in a submicrometric region; the detection of any surface or buried metallization is a straightforward application for microelectronics. The analysis is performed as a function of the frequency in the microwave range and, further on, the data can be transformed in time domain for one dimensional tomography. The authors will show that microwave spectroscopy can be performed by means of standard coaxial pins employed as probes for measurements both in reflection and transmission mode, giving the information of the frequency dependent properties of the exploited material or structure by means of the measured impedance. Experiments are performed in the range between 1 and 18 GHz, and different dielectric samples are tested. In order to evaluate the surface and subsurface measuring capability, samples obtained by thin metallic film deposition on a silicon wafer and buried by a polymeric layer are realized and characterized.