Radiation hardness properties of full-3D active edge silicon sensors

Full-three-dimensional (3D) pixel sensors, with electrodes penetrating through the entire silicon wafer, were fabricated at the Stanford Nanofabrication Facility, Stanford, California, USA. They have 71-μm-inter-electrode spacing, active edges and a compatible geometry to the ATLAS pixel detector readout electronics. Several samples were irradiated with neutrons to different doses up to an equivalent fluence of 8.6×10¹⁵ n_{1 MeVeq} cm^-2. This corresponds to the integrated fluence expected after ∼5 years at the Large Hadron Collider (LHC) with a luminosity of 10³⁵ cm^-2 s^-1 at 4 cm from the interaction point, where the ATLAS B-Layer is placed. Before and after irradiation, signals were generated by a 1060 nm infrared laser calibrated to inject a charge of 14 fC. This corresponds to ∼3.5 minimum ionizing particles and should not perturb the charge status of the radiation-induced defects. After 8.6×10¹⁵ n_{1 MeVeq} cm^-2 the signal collected was ∼38% and corresponded to ∼7200e^- for a substrate thickness of 235 μm. Signal efficiency, radiation-induced leakage current and related damage parameters are discussed here and compared with simulations. Full-3D silicon detectors with active edges are being considered for forward proton tagging at the LHC, for the ATLAS pixel B-layer replacement and for the ATLAS pixel upgrade.