New designs of silicon pixel detectors fabricated from normal and oxygen-enriched silicon substrates

New designs of silicon pixel detectors have been developed for more radiation-hard CMS forward pixel sensors. The new designs differ from our previous ones in that the guard rings on the n⁺ side are replaced with a single wide (640 μm) n⁺ implant, and the n⁺ side and the edge region of the p⁺ side are grounded, giving more graded potential distribution over the guard rings after irradiation. Thus, these designs have advantages for safe operation of the detectors at a high depletion voltage and for stability of readout chips. All designs were fabricated from normal and oxygen-enriched silicon substrates, and the radiation hardness effects for neutron (1 MeV equivalent) and proton (24 GeV) irradiation of these detectors were compared. Other electrical characteristics of these detectors such as leakage current, potential distribution over the guard rings and full depletion voltage were obtained using standard measurement techniques (I-V, V-V and TCT) before and after irradiation