Effect of gamma irradiation on characteristics of FOXFET biased edge-on silicon strip detector

Edge-on silicon strip detectors were designed and fabricated. The dependence of main detector parameters of importance such as leakage current, dynamic resistance of integrated FOXFET biasing structure, and radiation hardness on ionizing irradiation was investigated. Irradiation tests were carried out at different gate electric field using Co⁶⁰ gamma-ray source up to 0.2 Mrd(SiO₂). Optimized low-temperature segregation anneal results in a substantial decrease of detector leakage current. Dynamic resistance as high as 2 GΩ was achieved on nonirradiated detectors for channel width and length of 10 μm. Main factors influencing the radiation hardness of strip detector with FOXFET biasing structure are leakage current and strip potential. Leakage current increases detector noise and lowers the dynamic resistance of FOXFET biasing structure. The strip voltage shift toward positive voltages shows a strong dependence on gate electric field applied during the irradiation. The radiation hardness of oxide and composite nitride/oxide dielectric layers in MIS capacitor structures was investigated. Composite nitride/oxide (MNOS) capacitors show improved radiation hardness compared to oxide (MOS) capacitors in case of applied positive gate electric field.