Radiation resistant LGAD design Ferrero, M.; Arcidiacono, R.; Barozzi, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2019, Letnik:
919
Journal Article
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In this paper, we report on the radiation resistance of 50-micron thick Low Gain Avalanche Diodes (LGAD) manufactured at the Fondazione Bruno Kessler (FBK) employing different dopings in the gain ...layer. LGADs with a gain layer made of Boron, Boron low-diffusion, Gallium, Carbonated Boron and Carbonated Gallium have been designed and successfully produced at FBK. These sensors have been exposed to neutron fluences up to ϕn∼3⋅1016n∕cm2 and to proton fluences up to ϕp∼9⋅1015p∕cm2 to test their radiation resistance. The experimental results show that Gallium-doped LGAD are more heavily affected by the initial acceptor removal mechanism than those doped with Boron, while the addition of Carbon reduces this effect both for Gallium and Boron doping. The Boron low-diffusion gain layer shows a higher radiation resistance than that of standard Boron implant, indicating a dependence of the initial acceptor removal mechanism upon the implant density.
First FBK production of 50 μm ultra-fast silicon detectors Sola, V.; Arcidiacono, R.; Boscardin, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2019, Letnik:
924
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Fondazione Bruno Kessler (FBK, Trento, Italy) has recently delivered its first 50 μm thick production of Ultra-Fast Silicon Detectors (UFSD), based on the Low-Gain Avalanche Diode design. These ...sensors use high resistivity Si-on-Si substrates, and have a variety of gain layer doping profiles and designs based on Boron, Gallium, Carbonated Boron and Carbonated Gallium to obtain a controlled multiplication mechanism. Such variety of gain layers will allow identifying the most radiation hard technology to be employed in the production of UFSD, to extend their radiation resistance beyond the current limit of ϕ∼ 1015 neq/cm2. In this paper, we present the characterisation, the timing performance, and the results on radiation damage tolerance of this new FBK production.
In this paper we present the numerical simulation of silicon detectors with internal gain as the main tool for 4-dimensional (4D) particle trackers design and optimization. The Low-Gain Avalanche ...Diode (LGAD) technology and its present limitations are reviewed with the aim of introducing the Resistive AC-Coupled Silicon Detectors (RSD) paradigm as a case study of our investigation. Authors here present Spice-like and 2D/3D Technological Computer-Aided Design (TCAD) simulations to characterize sensors in terms of both their electrostatic behavior, capacitive (dynamic) coupling and radiation-hardness performances, showing the methodological approach used in order to extract the set of layout rules allowing the release of RSD1, the incoming production run at Fondazione Bruno Kessler (FBK) of next-generation silicon detectors for 4D tracking with intrinsic 100% fill-factor.
Abstract
Recent advancements in Monolithic Active Pixel Sensors (MAPS) demonstrated the ability to operate in high radiation environments of up to multiple kGy’s, which increased their appeal as ...sensors for high-energy physics detectors. The most recent example in such application is the new ALICE inner tracking system, entirely instrumented with CMOS MAPS, that covers an area of about 10 m
2
. However, the full potential of such devices has not yet been fully exploited, especially in respect of the size of the active area, power consumption, and timing capabilities.
The ARCADIA project is developing Fully Depleted (FD) MAPS with an innovative sensor design, that uses a proprietary processing of the backside to improve the charge collection efficiency and timing over a wide range of operational and environmental conditions. The innovative sensor design targets very low power consumption, of the order of 20 mW cm
−2
at 100 MHz cm
−2
hit flux, to enable air-cooled operations of the sensors. Another key design parameter is the ability to further reduce the power regime of the sensor, down to 5 mW cm
−2
or better, for low hit rates like e.g. expected in space experiments. In this contribution, we present a comparison between the detector characteristics predicted with Technology Computer Aided Design (TCAD) simulations and the ones measured experimentally. The comparison focuses on the current-voltage (IV) and capacitance-voltage (CV) characteristics, as well as noise estimated from in-pixel capacitances of passive/active pixel matrices. In view of the targeted applications of this technology, an emphasis is set on the modeling of X-ray induced radiation damage at the Si-SiO
2
interface and the impact on the in-pixel sensor capacitance. The so-called new Perugia model has been used in the simulations to predict the sensor performance after total ionizing doses of up to 10 Mrad.
A single-photon avalanche diode-based pixel array for the analysis of fluorescence phenomena is presented. Each 180 times 150 - mum 2 pixel integrates a single photon detector combined with an active ...quenching circuit and a 17-bit digital events counter. On-chip master logic provides the digital control phases required by the pixel array with a full programmability of the main timing synchronisms. The pixel exhibits an average dark count rate of 3 kcps and a dynamic range of over 120-dB in time uncorrelated operation. A complete characterization of the single photon avalanche diode characteristics is reported. Time-resolved fluorescence measurements have been demonstrated by detecting the fluorescence decay of quantum-dot samples without the aid of any optical filters for excitation laser light cutoff.
In scintillation and dosimetry applications, the increasing interest on the use of colloidal quantum dots (QDs) in comparison with organic fluorophores is mainly due to their easier chemical ...processability, narrower photoluminescence (PL) emission, and higher cross-section for ionizing radiation. The development of scintillators and dosimeter based on QDs, however, relies on a deep understanding of the effects of ionizing radiation on QD structures. In this paper, we present the optical characterization of colloidal cadmium-free InGaP/ZnS core–shell QDs embedded in polydimethylsiloxane (PDMS) and irradiated with 2 MeV protons (H+) in the fluence range of 1014 to 1015 H+ cm–2. Steady-state PL measurements of the irradiated samples show a decrease of the average QD PL intensity, indicating the introduction of PL quenching centers. Time-resolved PL measurements, acquired with a time-correlated single photon counting system, provide a way to probe the radiation-induced change in the carrier recombination dynamics of the QDs. A detailed analysis of the time-resolved PL curves demonstrates the presence of PL quenching defects localized both at the inner (core) and at the outer (shell) structure of the nanocrystal. The radiation-induced change in the QD optical properties, coupled with a suitable radiation hardness of the PDMS in these irradiation conditions, open the way for possible future applications related to dosimetry systems based on QDs as nanostructured sensing elements.
Abstract
The ARCADIA collaboration is developing fully-depleted (FD) Monolithic Active Pixel Sensors (MAPS) in a 110 nm CMOS process in collaboration with LFoundry. The sensor design incorporates an ...n+ collection node within a n-type epi-layer on top of a high-resistivity n-type substrate and p+ backside. Thus, the pn-junction sits on the backside and through an applied backside bias, the full substrate gets depleted. The targeted applications of this technology range from future high energy physics experiments to space applications, and medical and industrial scanners. Together, these applications set the minimum requirements on the detector: data collection at hit rates of (10–100) MHz/cm
2
, full signal processing within (1–10) μs, maximum power consumption (5–20) mW/cm
2
and radiation tolerances of up to 3.4 Mrad or 6.2 × 10
12
1 MeV neutron equivalent fluence. In order to proof the performance of the technology, a demonstrator chip of 512 × 512 pixels with 25 μm pitch was designed and fabricated in a first engineering run in 2021, together with additional test structures of pixel and strip arrays with different pitches and sensor geometries. The production run has produced functional passive and active pixel matrices. Earlier studies have shown that positive oxide charges and traps at the Si-SiO
2
interface, introduced by ionising radiation, affect the depletion region around the collection electrode, increasing the pixel capacitance. By varying the gap size between collection node and pwells, the geometry can be optimised to keep the capacitance low also after irradiation. To study the performance after irradiation, of the optimised diode designs, the passive pixel matrices were irradiated with doses up to 10 Mrad (SiO
2
) using a X-ray tube with a Tungsten anode. The measurements are complemented by TCAD simulations. The maximum capacitance increase after irradiation was found to reach 6 and 12 fF/pixel for pixel pitches of 25 and 50 μm, respectively. The relative capacitance increase after irradiation has hereby been found to reach up to 250% after a dose of 10 Mrad.
Single-photon avalanche diode (SPAD) arrays fabricated in a 180-nm CMOS technology with a high-voltage option have been exposed to calibrated neutron and X-ray sources to evaluate their radiation ...tolerance. The technology is being investigated in view of the design of low material budget detectors for charged particle tracking based on the coincidence of the signals coming from two or more overlapping layers of SPAD sensors. Each element in the array is a monolithic detector including the processing electronics together with the diode in the same substrate. Different sensor dimensions and structures have been implemented in the test chip to thoroughly explore the technology features. This paper will present and discuss the results from the characterization, in terms of dark count rate, of SPAD arrays irradiated with X-ray doses reaching 1 Mrad(SiO 2 ) and with neutron fluences up to <inline-formula> <tex-math notation="LaTeX">10^{11}~1 </tex-math></inline-formula>-MeV neutron equivalent cm<inline-formula> <tex-math notation="LaTeX">^{-2} </tex-math></inline-formula>.
Abstract
The development of novel Monolithic Active Pixel Sensor (MAPS) technologies has been pursued by several collaborations in the last two decades. The ARCADIA project aims to design fully ...depleted MAPS for medical, space, HEP and X-ray detection applications, that can be produced with a commercial 110 nm CMOS production process. Among the test structures of the first two engineering runs of the project, passive pixel arrays with different pitches and layouts were included. The main characteristics of the produced devices in terms of dark current, depletion voltage, punch through current and pixel capacitance have been evaluated from IV and CV characteristics of the pixel arrays. Groups of four samples have been extracted from as many different positions within each wafer and electrically characterized to obtain information on the variability in the pixel operating voltage range and in the pixel dark current, reflecting variations related to the employed production process. The experimental data demonstrated a good uniformity in the considered parameters for different sample positions within the produced wafers, as well as for samples extracted from different wafers with the same substrate type.
Single-photon avalanche diodes (SPADs) fabricated using two different CMOS technologies were exposed to a neutron source up to a maximum fluence of <inline-formula> <tex-math notation="LaTeX">3\times ...10^{11}\,\,1 </tex-math></inline-formula>-MeV neutron equivalent cm −2 . Significant changes in the dark count rate (DCR), with a strong dependence on the fluence and the device active area, were detected after irradiation. A model for the probability of DCR degradation, accounting for the source spectrum and the geometry of the device under test (DUT), was proposed and proved to be in good agreement with experimental data. The model may be helpful in performing worst-case analysis of SPAD-based detection systems under neutron irradiation.
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