The ATLAS community is facing the last stages prior to the production of the upgraded silicon strip Inner Tracker for the High-Luminosity Large Hadron Collider. An extensive Market Survey was carried ...out in order to evaluate the capability of different foundries to fabricate large area silicon strip sensors, satisfying the ATLAS specifications. The semiconductor manufacturing company, Infineon Technologies AG, was one of the two foundries, along with Hamamatsu Photonics K.K., that reached the last stage of the evaluation for the production of the new devices. The full prototype wafer layout for the participation of Infineon, called ATLAS17LS-IFX, was designed using a newly developed Python-based Automatic Layout Generation Tool, able to rapidly design sensors with different characteristics and dimensions based on a few geometrical and technological input parameters. This work presents the layout design process and the results obtained from the evaluation of the new Infineon large area sensors before and after proton and neutron irradiations, up to fluences expected in the inner layers of the future ATLAS detector.
Humidity sensitivity of large area silicon sensors: Study and implications Fernández-Tejero, J.; Allport, P.P.; Aviñó, O. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2020, Letnik:
978, Številka:
C
Journal Article
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The production of large area sensors is one of the main challenges that the ATLAS collaboration faces for the new Inner-Tracker full-silicon detector. During the prototype fabrication phase for the ...High Luminosity Large Hadron Collider upgrade, several ATLAS institutes observed indications of humidity sensitivity of large area sensors, even at relative humidities well below the dew point. Specifically, prototype Barrel and End-Cap silicon strip sensors fabricated in 6-inch wafers manifest a prompt decrease of the breakdown voltage when operating under high relative humidity, adversely affecting the performance of the sensors. In addition to the investigation of these prototype sensors, a specific fabrication batch with special passivation is also studied, allowing for a deeper understanding of the responsible mechanisms.
This work presents an extensive study of this behaviour on large area sensors. The locations of the hotspots at the breakdown voltage at high humidity are revealed using different infrared thermography techniques. Several palliative treatments are attempted, proving the influence of sensor cleaning methods, as well as baking, on the device performance, but no improvement on the humidity sensitivity was achieved. Furthermore, a study of the incidence of the sensitivity in different batches is also presented, introducing a hypothesis of the origins of the humidity sensitivity associated to the sensor edge design, together with passivation thickness and conformity. Several actions to be taken during sensor production and assembly are extracted from this study, in order to minimize the impact of humidity sensitivity on the performance of large area silicon sensors for High Energy Physics experiments.
The upgrade of the LHC to the High Luminosity LHC will challenge the silicon strip detector performance with high fluence and long operation time. Sensors have been designed and tests on charge ...collection and electrical performance have been carried out in order to evaluate their behaviour. Besides that, it is important to understand and predict the long-term evolution of the sensor properties. In this work, detailed studies on the annealing behaviour of ATLAS12 strip sensors designed by the ITK Strip Sensor Working Group and irradiated from 5×1013neqcm−2 to 2×1015neqcm−2 are presented. Systematic charge collection and leakage current measurements have been carried out during the annealing process until break-down or the appearance of charge multiplication. The annealing was carried out, separating the sensors into two groups being either annealed at 23°C or 60°C. Sensors showing charge multiplication have been then kept at high voltage for a long time in order to monitor their stability. The difference in the annealing behaviour between the two temperatures has been analysed and compared to similar measurements on n-type sensors and with a theoretical model. From the impedance measurements for the samples irradiated to low fluences it was possible to extract the effective doping concentration. This was compared to similar measurements on n-type sensors and with a theoretical model.
The inner tracker of the ATLAS detector is scheduled to be replaced by a completely new silicon-based inner tracker (ITk) for the Phase-II of the CERN LHC (HL-LHC). The silicon strip detector covers ...the volume 40<R<100 cm in the radial and |z|<300 cm in the longitudinal directions. The silicon sensors for the detector will be fabricated using the n+-on-p 6-inch wafer technology, for a total of 22,000 wafers. Intensive studies were carried out on the final prototype sensors ATLAS17LS fabricated by Hamamatsu Photonics (HPK). The charge collection properties were examined using penetrating 90Sr β-rays and the ALIBAVA fast readout system for the miniature sensors of 1 cm ×1 cm in area. The samples were irradiated by protons in the 27 MeV Birmingham Cyclotron, the 70 MeV CYRIC at Tohoku University, and the 24 GeV CERN-PS, and by neutrons at Ljubljana TRIGA reactor for fluence values up to 2 × 1015 neq/cm2. The change in the charge collection with fluence was found to be similar to the previous prototype ATLAS12, and acceptable for the ITk. Sensors with two active thicknesses, 300μm (standard) and 240μm (thin), were compared and the difference in the charge collection was observed to be small for bias voltages up to 500 V. Some samples were also irradiated with gamma radiation up to 2 MGy, and the full depletion voltage was found to decrease with the dose. This was caused by the Compton electrons due to the 60Co gamma radiation. To summarize, the design of the ATLAS17LS and technology for its fabrication have been verified for implementation in the ITk. We are in the stage of sensor pre-production with the first sensors already delivered in January of 2020.
Miniature sensors with external dimensions of 10 mm x 10 mm were produced together with full-size sensors for the innermost ring (R0) of the end-cap part in the upgraded ATLAS inner tracker (ITk). ...AC- and DC-coupled n-type strips with three different pitches (wide, default and narrow) were processed on high-resistivity p-type FZ silicon substrates by Hamamatsu Photonics. The miniature sensors were irradiated with 70-MeV protons at CYRIC, Tohoku University (Japan) and reactor neutrons at the Jožef Stefan Institute (Slovenia) to three different 1-MeV neutron equivalent fluences: 0.5, 1 and 2 x 1015neqcm−2. The upper fluence range exceeds the highest anticipated in the innermost part of the ATLAS ITk-Strips over the HL-LHC lifetime (∼1.25 × 1015neqcm2). The charge collection in the test sensors was evaluated systematically using a 90Sr β-source and an Alibava analogue readout system at reverse-bias voltages up to 1000 V.
•The charge collection in the test sensors was evaluated systematically.•The collected charge increases with the applied voltage.•At higher voltages the effect of multiplication can be seen.•The multiplication becomes higher at long annealing times.
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