Processing of AC-coupled n-in-p pixel detectors on MCz silicon using atomic layer deposited aluminium oxide

We report on the fabrication of capacitively (AC) coupled n(+)-in-p pixel detectors on magnetic Czochralski silicon substrates. In our devices, we employ a layer of aluminium oxide (Al2O3) grown by atomic layer deposition (ALD) as dielectric and field insulator, instead of the commonly used silicon dioxide (SiO2). As shown in earlier research, Al2O3 thin films exhibit high negative oxide charge, and can thus serve as a substitute for p-stop/p-spray insulation implants between pixels. In addition, they provide far higher capacitance densities than SiO2 due to their high dielectric constant, permitting more efficient capacitive coupling of pixels. Furthermore, metallic titanium nitride (TiN) bias resistors are presented as an alternative to punch-through or poly-Si resistors. Devices obtained by the above mentioned process are characterized by capacitance-voltage and current-voltage measurements, and by 2 MeV proton microprobe. Results show the expected high negative charge of the Al2O3 dielectric, uniform charge collection efficiency over large areas of pixels, and acceptable leakage current densities.Peer reviewe

Quality assessment of cadmium telluride as a detector material for multispectral medical imaging

Cadmiumtelluride (CdTe) is a high-Z material with excellent photon radiation absorption properties, making it a promising material to include in radiation detection technologies. However, the brittleness of CdTe crystals as well as their varying concentration of defects necessitate a thorough quality assessment before the complex detector processing procedure. We present our quality assessment of CdTe as a detector material for multispectralmedical imaging, a research which is conducted as part of the Consortium Project Multispectral Photon-counting for Medical Imaging and Beam characterization (MPMIB). The aim of the project is to develop novel CdTe detectors and obtain spectrum-per-pixel information that make the distinction between different radiation types and tissues possible. To evaluate the defect density inside the crystals - which can deteriorate the detector performance - we employ infrared microscopy (IRM). Posterior data analysis allows us to visualise the defect distributions as 3D defect maps. Additionally, we investigate front and backside differences of the material with current-voltage (IV) measurements to determine the preferred surface for the pixelisation of the crystal, and perform test measurements with the prototypes to provide feedback for further processing. We present the different parts of our quality assessment chain and will close with first experimental results obtained with one of our prototype photon-counting detectors in a small tomographic setup.Peer reviewe

Characterization of magnetic Czochralski silicon devices with aluminium oxide field insulator : effect of oxygen precursor on electrical properties and radiation hardness

Aluminium oxide (Al2O3) has been proposed as an alternative to thermal silicon dioxide (SiO2) as field insulator and surface passivation for silicon detectors, where it could substitute p-stop/p-spray insulation implants between pixels due to its negative oxide charge, and enable capacitive coupling of segments by means of its higher dielectric constant. Al2O3 is commonly grown by atomic layer deposition (ALD), which allows the deposition of thin layers with excellent precision. In this work, we report the electrical characterization of single pad detectors (diodes) and MOS capacitors fabricated on magnetic Czochralski silicon substrates and using Al2O3 as field insulator. Devices are studied by capacitance-voltage, current-voltage, and transient current technique measurements. We evaluate the influence of the oxygen precursors in the ALD process, as well as the effect of gamma irradiation, on the properties of these devices. We observe that leakage currents in diodes before the onset of breakdown are low for all studied ALD processes. Charge collection as measured by transient current technique (TCT) is also independent of the choice of oxygen precursor. The Al2O3 films deposited with O-3 possess a higher negative oxide charge than films deposited by H2O, However, in diodes a higher oxide charge is linked to earlier breakdown, as has been predicted by simulation studies. A combination of H2O and O-3 precursors results in a good compromise between the beneficial properties provided by the respective individual precursors.Peer reviewe

Beam test performance of a prototype module with Short Strip ASICs for the CMS HL-LHC tracker upgrade

The Short Strip ASIC (SSA) is one of the four front-end chips designed for the upgrade of the CMS Outer Tracker for the High Luminosity LHC. Together with the Macro-Pixel ASIC (MPA) it will instrument modules containing a strip and a macro-pixel sensor stacked on top of each other. The SSA provides both full readout of the strip hit information when triggered, and, together with the MPA, correlated clusters called stubs from the two sensors for use by the CMS Level-1 (L1) trigger system. Results from the first prototype module consisting of a sensor and two SSA chips are presented. The prototype module has been characterized at the Fermilab Test Beam Facility using a 120 GeV proton beam

Test beam performance of a CBC3-based mini-module for the Phase-2 CMS Outer Tracker before and after neutron irradiation

The Large Hadron Collider (LHC) at CERN will undergo major upgrades to increase the instantaneous luminosity up to 5–7.5×10$^{34}$ cm$^{-2}$s$^{-1}$. This High Luminosity upgrade of the LHC (HL-LHC) will deliver a total of 3000–4000 fb-1 of proton-proton collisions at a center-of-mass energy of 13–14 TeV. To cope with these challenging environmental conditions, the strip tracker of the CMS experiment will be upgraded using modules with two closely-spaced silicon sensors to provide information to include tracking in the Level-1 trigger selection. This paper describes the performance, in a test beam experiment, of the first prototype module based on the final version of the CMS Binary Chip front-end ASIC before and after the module was irradiated with neutrons. Results demonstrate that the prototype module satisfies the requirements, providing efficient tracking information, after being irradiated with a total fluence comparable to the one expected through the lifetime of the experiment

Beam test performance of a prototype module with Short Strip ASICs for the CMS HL-LHC tracker upgrade

Copyright © 2022 CERN for the benefit of the CMS Tracker collaboration. The Short Strip ASIC (SSA) is one of the four front-end chips designed for the upgrade of the CMS Outer Tracker for the High Luminosity LHC. Together with the Macro-Pixel ASIC (MPA) it will instrument modules containing a strip and a macro-pixel sensor stacked on top of each other. The SSA provides both full readout of the strip hit information when triggered, and, together with the MPA, correlated clusters called stubs from the two sensors for use by the CMS Level-1 (L1) trigger system. Results from the first prototype module consisting of a sensor and two SSA chips are presented. The prototype module has been characterized at the Fermilab Test Beam Facility using a 120 GeV proton beam.BMWFW and FWF (Austria); FNRS and FWO (Belgium); CERN; MSE and CSF (Croatia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); NKFIA K124850, and Bolyai Fellowship of the Hungarian Academy of Sciences (Hungary); DAE and DST (India); INFN (Italy); PAEC (Pakistan); SEIDI, CPAN, PCTI and FEDER (Spain); Swiss Funding Agencies (Switzerland); MST (Taipei); STFC (United Kingdom); DOE and NSF (U.S.A.). This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 884104 (PSI-FELLOW-III-3i). Individuals have received support from HFRI (Greece)

Evaluation of HPK +- planar pixel sensors for the CMS Phase-2 upgrade

Data availability: Data will be made available on request.The article archived on this institutional repository is a preprint made available on arXiv, arXiv:2212.04793v1 [physics.ins-det] (license: CC BY-NC-ND 4.0 - https://creativecommons.org/licenses/by-nc-nd/4.0/). It has not been certified by peer review. You are advised to consult the final version published by Elsevier at: https://doi.org/10.1016/j.nima.2023.168326 (the pubished version is copyright © 2023 Elsevier B.V. All rights reserved).To cope with the challenging environment of the planned high luminosity upgrade of the Large Hadron Collider (HL-LHC), scheduled to start operation in 2029, CMS will replace its entire tracking system. The requirements for the tracker are largely determined by the long operation time of 10 years with an instantaneous peak luminosity of up to 7.5 × 10^34 cm^−2^s−1 in the ultimate performance scenario. Depending on the radial distance from the interaction point, the silicon sensors will receive a particle fluence corresponding to a non-ionizing energy loss of up to Φeq = 3.5 × 10^16 cm^−2. This paper focuses on planar pixel sensor design and qualification up to a fluence of Φeq = 1.4 × 10^16 cm^−2. For the development of appropriate planar pixel sensors an R&D program was initiated, which includes n+-p sensors on 150 mm (6'') wafers with an active thickness of 150 μm with pixel sizes of 100 × 25 μm^2 and 50 × 50 μm^2 manufactured by Hamamatsu Photonics K.K. (HPK). Single chip modules with ROC4Sens and RD53A readout chips were made. Irradiation with protons and neutrons, as well was an extensive test beam campaign at DESY were carried out. This paper presents the investigation of various assemblies mainly with ROC4Sens readout chips. It demonstrates that multiple designs fulfill the requirements in terms of breakdown voltage, leakage current and efficiency. The single point resolution for 50 × 50 μm^2 pixels is measured as 4.0 μm for non-irradiated samples, and 6.3 μm after irradiation to Φeq = 7.2 × 10^15 cm^−2.This work was supported by the German Federal Ministry of Education and Research (BMBF) in the framework of the “FIS-Projekt - Fortführung des CMS-Experiments zum Einsatz am HL-LHC: Verbesserung des Spurdetektors für das Phase-2 Upgrade des CMS-Experiments” and supported by the H2020 project AIDA-2020, GA no. 654168. The measurements leading to these results have been performed at the Test Beam Facility at DESY Hamburg (Germany), a member of the Helmholtz Association (HGF). The tracker groups gratefully acknowledge financial support from the following funding agencies: BMWFW and FWF (Austria); FNRS, Belgium and FWO (Belgium); CERN, Switzerland; MSE and CSF (Croatia); Academy of Finland, Finland, MEC, Canada, and HIP (Finland); CEA, United States and CNRS/IN2P3 (France); BMBF, DFG, United States, and HGF (Germany); GSRT (Greece); NKFIA K124850, and Bolyai Fellowship of the Hungarian Academy of Sciences (Hungary); DAE, India and DST (India); INFN (Italy); PAEC (Pakistan); SEIDI, Spain, CPAN, PCTI and FEDER (Spain); Swiss Funding Agencies (Switzerland); MST (Taipei); STFC (United Kingdom); DOE and NSF (U.S.A.). This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 884104 (PSI-FELLOW-III-3i). Individuals have received support from HFRI (Greece)

Evaluation of planar silicon pixel sensors with the RD53A readout chip for the Phase-2 Upgrade of the CMS Inner Tracker

The Large Hadron Collider at CERN will undergo an upgrade in order to increase its luminosity to 7.5 × 10³⁴ cm⁻²s⁻¹. The increased luminosity during this High-Luminosity running phase, starting around 2029, means a higher rate of proton-proton interactions, hence a larger ionizing dose and particle fluence for the detectors. The current tracking system of the CMS experiment will be fully replaced in order to cope with the new operating conditions. Prototype planar pixel sensors for the CMS Inner Tracker with square 50 μm × 50 μm and rectangular 100 μm × 25 μm pixels read out by the RD53A chip were characterized in the lab and at the DESY-II testbeam facility in order to identify designs that meet the requirements of CMS during the High-Luminosity running phase. A spatial resolution of approximately 3.4 μm (2 μm) is obtained using the modules with 50 μm × 50 μm (100 μm × 25 μm) pixels at the optimal angle of incidence before irradiation. After irradiation to a 1 MeV neutron equivalent fluence of Φeq = 5.3 × 10¹⁵ cm⁻², a resolution of 9.4 μm is achieved at a bias voltage of 800 V using a module with 50 μm × 50 μm pixel size. All modules retain a hit efficiency in excess of 99% after irradiation to fluences up to 2.1 × 10¹⁶ cm⁻². Further studies of the electrical properties of the modules, especially crosstalk, are also presented in this paper

Dual-readout calorimetry: Present status and perspective

Dual-readout calorimetry is now a mature and well-known technology which guarantees excellent electromagnetic and hadronic resolution in the same detector. It has recently being proposed in the framework of IDEA (Innovative Detector for Electron-Positron Accelerators) for both Future Circular Collider (FCC-ee) and Circular Electron-Positron Collider (CEPC). After being extensively tested on prototypes, the dual-readout calorimetry is now moving toward a technology design study in order to be realistically available for an experiment. In this context, a full simulation of the calorimeter has been developed and used to estimate the expected performance of the detector. At the same time, the development of a novel technique for mass production of the detector modules, at an effective cost, is ongoing. As a first step, an electromagnetic-size prototype is under construction for a testbeam data taking originally foreseen in November 2020 and now moved to spring 2021, due to the Covid-19 pandemic spread