Total-ionizing dose (TID) and displacement damage (DD) are investigated in SiC power MOSFETs at ultrahigh doses with 10-keV X-ray and 3-MeV protons. Significant parametric shifts in the electrical ...responses of the devices are observed depending on the bias condition and on the fabrication technology. Worst TID degradation is measured when positive gate bias is applied during the irradiation, due to positive charge trapping in the gate oxide. Devices built in the latest generation SiC technology reveal a smaller subthreshold swing degradation, thanks to a better quality of the SiC/SiO2 interface. Devices exposed to 3-MeV protons exhibit a complex combination of TID and DD effects. The <inline-formula> <tex-math notation="LaTeX">I-V </tex-math></inline-formula> and capacitance-voltage (<inline-formula> <tex-math notation="LaTeX">C-V </tex-math></inline-formula>) measurements in SiC power MOSFETs identify two main degradation mechanisms: 1) TID-induced charge trapping in the gate oxide and SiC/SiO2 interface and 2) DD-induced lattice damage in the SiC drift region, which degrades the series resistance of the devices.
We studied device-to-device variations as a function of total dose in MOSFETs, using specially designed test structures and procedures aimed at maximizing matching between transistors. Degradation in ...nMOSFETs is less severe than in pMOSFETs and does not show any clear increase in sample-to-sample variability due to the exposure. At doses smaller than 1 Mrad( SiO 2 ) variability in pMOSFETs is also practically unaffected, whereas at very high doses-in excess of tens of Mrad( SiO 2 )-variability in the on-current is enhanced in a way not correlated to pre-rad variability. The phenomenon is likely due to the impact of random dopant fluctuations on total ionizing dose effects.
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>.
The very high radiation fluences expected at the high-luminosity large hadron collider (LHC) impose new challenges in terms of design of radiation resistant silicon detectors. The choice to use ...p-type substrates to improve the charge collection efficiency involves an optimization of the strip isolation to interrupt the inversion layer between the n± implants, limiting the breakdown voltage. To this purpose, TCAD modeling and simulation schemes, already developed and validated at typical LHC fluences have to be adapted to take into account effects usually neglected at lower fluences. To better understand in a comprehensive framework, the complex and articulated phenomena related to bulk and surface radiation damage, measurements on test structures and sensors, as well as TCAD simulations related to bulk, surface and interface effects, have been carried out. In particular, we have studied the properties of the SiO 2 layer and of the Si-SiO 2 interface, using MOS capacitors and gate-controlled diodes (gated diodes) manufactured by different vendors on a high-resistivity p-type silicon before and after irradiation with X-rays in the range from 50 krad to 10 Mrad. In this paper, we present the results of the experimental characterizations as well as the simulation findings, in order to analyze the effects of the interface traps on the strip isolation. This analysis helps us to validate the model and to identify the most sensitive technological and design parameters to be optimized for the design of advanced 2-D and 3-D silicon radiation detectors.
The iMPACT project tracker and calorimeter Mattiazzo, S.; Bisello, D.; Giubilato, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2017, Letnik:
845
Journal Article
Recenzirano
Odprti dostop
In recent years the use of hadrons for cancer radiation treatment has grown in importance, and many facilities are currently operational or under construction worldwide. To fully exploit the ...therapeutic advantages offered by hadron therapy, precise body imaging for accurate beam delivery is decisive. While traditional X-ray Computed Tomography (xCT) fails in providing 3D images with the precision required for hadrons treatment guidance, Proton Computer Tomography (pCT) scanners, currently in their R&D phase, can. A pCT scanner consists of a tracker system, to track protons, and of a calorimeter, to measure their residual energy. In this paper we will present the iMPACT project, which foresees a novel proton tracking detector with higher scanning speed, better spatial resolution and lower material budget with respect to present state-of-the-art detectors, leading to enhanced performances. The tracker will be matched to a fast, highly segmented proton range calorimeter.
The ALICE experiment at CERN will undergo a major upgrade in the second Long LHC Shutdown in the years 2018–2019; this upgrade includes the full replacement of the Inner Tracking System (ITS), ...deploying seven layers of Monolithic Active Pixel Sensors (MAPS). For the development of the new ALICE ITS, the Tower-Jazz 0.18μm CMOS imaging sensor process has been chosen as it is possible to use full CMOS in the pixel and different silicon wafers (including high resistivity epitaxial layers). A large test campaign has been carried out on several small prototype chips, designed to optimize the pixel sensor layout and the front-end electronics. Results match the target requirements both in terms of performance and of radiation hardness. Following this development, the first full scale chips have been designed, submitted and are currently under test, with promising results. A telescope composed of 4 planes of Mimosa-28 and 2 planes of Mimosa-18 chips is under development at the DAFNE Beam Test Facility (BTF) at the INFN Laboratori Nazionali di Frascati (LNF) in Italy with the final goal to perform a comparative test of the full scale prototypes. The telescope has been recently used to test a Mimosa-22THRb chip (a monolithic pixel sensor built in the 0.18μm Tower-Jazz process) and we foresee to perform tests on the full scale chips for the ALICE ITS upgrade at the beginning of 2015. In this contribution we will describe some first measurements of spatial resolution, fake hit rate and detection efficiency of the Mimosa-22THRb chip obtained at the BTF facility in June 2014 with an electron beam of 500MeV.
The CLARO8 chip has been designed for single-photon counting in the upgraded RICH detector of the LHCb experiment at CERN. The chip has 8 channels with 5ns peaking time and a recovery time better ...than 25ns. Each channel is made of a charge amplifier with 2-bit settable attenuation, plus a comparator with a 6-bit settable threshold, and the configuration register is protected against Single Event Upsets by triple modular redundancy. In order to ensure stable operation of the upgraded RICH detectors over the expected lifetime of the experiment after the upgrade, the performance of the CLARO8 in high radiation fields has been assessed. These chips will be exposed, during the whole upgrade running phase, to a total ionizing dose of 200krad, a neutron fluence of 3×1012 1MeVneq/cm2 and a high energy hadrons fluence of 1.2×1012cm−2. Systematic irradiation campaigns have been performed using ions, protons and mixed-field high-energy hadron beams. This paper describes the radiation hardness campaign of the CLARO8 chips and the main results of its extensive characterisation.
LePix—A high resistivity, fully depleted monolithic pixel detector Giubilato, P.; Bisello, D.; Chalmet, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2013, Letnik:
732
Journal Article
Recenzirano
The LePix project explores monolithic pixel sensors fabricated in a 90nm CMOS technology built over a lightly doped substrate. This approach keeps the advantages usually offered by Monolithic Active ...Pixel Sensors (MAPS), like a low input capacitance, having a single piece detector and using a standard CMOS production line, and adds the benefit of charge collection by drift from a depleted region several tens of microns deep into the substrate, therefore providing an excellent signal to noise ratio and a radiation tolerance superior to conventional un-depleted MAPS. Such sensors are expected to offer significant cost savings and reduction of power consumption for the same performance, leading to the use of much less material in the detector (less cooling and less copper), addressing one of the main limitations of present day particle tracking systems.
The latest evolution of the project uses detectors thinned down to 50μm to obtain back illuminated sensors operated in full depletion mode. By back-processing the chip and collecting the charge from the full substrate it is hence possible to efficiently detect soft X-rays up to 10keV. Test results from first successfully processed detectors will be presented and discussed.
PDF
