Fabrication and characterization of n-on-n silicon pixel detectors compatible with the Medipix2 readout chip

Pixel detectors for mammographic applications have been fabricated at ITC-irst on 800 μm thick silicon wafers adopting a double side n+-on-n fabrication technology. The activity aims at increasing the X-ray detection efficiency in the energy range of interest minimizing the risk of electrical discharges in hybrid systems operating at high voltages. The detectors, having a layout compatible with the Medipix2 photon counting chip, feature two different design solutions for the p-isolation between neighboring n+-pixels. We report on the characterization of the fabrication process and on preliminary results of electrical measurements on full detectors and pixel test structures. In particular, we found that the detectors can be reliably operated above the full depletion voltage regardless of the isolation design, that however, impacts the performances in terms of current-voltage characteristics, single pixel currents, inter-pixel resistances and inter-pixel capacitances