A Three-Dimensional Gated Diode Structure for Surface Parameter Characterization in a 3D Sensor Technology

We report on a three-dimensional gated diode test structure compatible with the latest fabrication technology developed at FBK for 3D pixel sensors oriented to the Phase 2 Upgrades at the High-Luminosity LHC (HL-LHC). Since this technology does not feature any patterned implanted region at the surface, standard gated diode structures cannot be implemented, thus hindering the extraction of surface parameters, in particular the surface generation velocity. A three-dimensional device is potentially suitable to this purpose, although some design constraints dictated by the fabrication process result in non-ideal current-voltage characteristics. Experimental results from the characterization of the first prototypes are presented and discussed with the aid of TCAD simulations. Modified geometries aimed to improve the accuracy of the extracted s0 values are also proposed.