Investigation of new micromachined coplanar probe for near-field microwave microscopy

The near-field measurement is based generally on the use of purely passive miniature sensors, dedicated to the capture of a component of the electromagnetic field. The performances of probe are characterized by two quantities: the sensitivity and spatial resolution, related to the geometry of the probe. Improve the spatial resolution of a sensor is often at the expense of sensitivity. In this work, we have presented non-conventional planar microwave probe. We achieved These electrical probes, based on a combination of coplanar line and the point effect, using the clean room techniques. The motivation behind the choice of a coplanar line with a pointed end is the fact of having a quasi-TEM propagation mode in order to have the performances of the conventional coaxial probes and secondly to have a compatibility with the integrated circuits for future microwave integrated microscopy. To prevent the oxidation problem, we choose gold as the metal structure. We used an oxidized silicon substrate in order to reduce losses in the silicon. Simulations and measurements results on a micro-strip line have shown that the probe is mainly sensitive to the normal electric field. The estimated sensitivity is 30 µV/(V/m). Using this CPW probe on a precision X–Y scanning table, 2D images of micro-strip line have been successfully constructed, indicated that the ratio of the resolution to the wavelength R/λ is around 0.66× 10^-4 at 1 GHz.