Showing papers in "IEEE Transactions on Nuclear Science in 2013"

Radiation Effects on Silica-Based Optical Fibers: Recent Advances and Future Challenges

Abstract: In this review paper, we present radiation effects on silica-based optical fibers. We first describe the mechanisms inducing microscopic and macroscopic changes under irradiation: radiation-induced attenuation, radiation-induced emission and compaction. We then discuss the influence of various parameters related to the optical fiber, to the harsh environments and to the fiber-based applications on the amplitudes and kinetics of these changes. Then, we focus on advances obtained over the last years. We summarize the main results regarding the fiber vulnerability and hardening to radiative constraints associated with several facilities such as Megajoule class lasers, ITER, LHC, nuclear power plants or with space applications. Based on the experience gained during these projects, we suggest some of the challenges that will have to be overcome in the near future to allow a deeper integration of fibers and fiber-based sensors in radiative environments.

Single Event Transients in Digital CMOS—A Review

Abstract: The creation of soft errors due to the propagation of single event transients (SETs) is a significant reliability challenge in modern CMOS logic. SET concerns continue to be exacerbated by Moore's Law technology scaling. This paper presents a review of digital single event transient research, including: a brief historical overview of the emergence of SET phenomena, a review of the present understanding of SET mechanisms, a review of the state-of-the-art in SET testing and modelling, a discussion of mitigation techniques, and a discussion of the impact of technology scaling trends on future SET significance.

Total Ionizing Dose Effects in MOS and Low-Dose-Rate-Sensitive Linear-Bipolar Devices

Abstract: An overview is presented of total ionizing dose (TID) effects in MOS and bipolar devices from a historical perspective, focusing primarily on work presented at the annual IEEE Nuclear and Space Radiation Effects Conference (NSREC). From the founding of the IEEE NSREC in 1964 until ~1976, foundational work led to the discovery of TID effects in MOS devices, the characterization of basic charge transport and trapping processes in SiO2, and the development of the first generations of metal-gate radiation-hardened MOS technologies. From ~1977 until ~1985, significant progress was made in the understanding of critical defects and impurities that limit the radiation response of MOS devices. These include O vacancies in SiO2, dangling Si bonds at the Si/SiO2 interface, and hydrogen. In addition, radiation-hardened Si-gate CMOS technologies were developed. From ~1986 until ~1997, a significant focus was placed on understanding postirradiation effects in MOS devices and implementing hardness assurance test methods to qualify devices for use in space systems. Enhanced low-dose-rate sensitivity (ELDRS) was discovered and investigated in linear bipolar devices and integrated circuits. From ~1998 until the present, an increasing focus has been placed on theoretical studies enabled by rapidly advancing computational capabilities, modeling and simulation, effects in ultra-thin oxides and alternative dielectrics to SiO2, and in developing a comprehensive model of ELDRS.

Evidence and Consequences of Ce $^{4+}$ in LYSO:Ce,Ca and LYSO:Ce,Mg Single Crystals for Medical Imaging Applications

Abstract: Lu2(1-x)Y2xSiO5:Ce (10 at% Y) single crystals co-doped with Ca2+ and Mg2+ were prepared by the Czochralski technique. It is shown that co-doping leads to significant improvements of the scintillation performances. Afterglow following X-ray excitation is reduced down to 200 ppm after 20 ms and light yield is increased from 28,000 ph/MeV up to 34,000 ph/MeV under 137Cs-662 keV excitation. X-ray Absorption Near Edge Spectroscopy (XANES) was used to demonstrate that a significant part of the Ce ions are stabilized in the Ce4+ oxidation state in co-doped crystals. A new scintillation mechanism involving Ce4+ is proposed.

Displacement Damage Effects in Irradiated Semiconductor Devices

Abstract: A review of radiation-induced displacement damage effects in semiconductor devices is presented, with emphasis placed on silicon technology. The history of displacement damage studies is summarized, and damage production mechanisms are discussed. Properties of defect clusters and isolated defects are addressed. Displacement damage effects in materials and devices are considered, including effects produced in silicon particle detectors, visible imaging arrays, and solar cells. Additional topics examined include NIEL scaling, carrier concentration changes, random telegraph signals, radiation hardness assurance, and simulation methods for displacement damage. Areas needing further study are noted.

Radiation Hardness Assurance Testing of Microelectronic Devices and Integrated Circuits: Radiation Environments, Physical Mechanisms, and Foundations for Hardness Assurance

Abstract: This document describes the radiation environments, physical mechanisms, and test philosophies that underpin radiation hardness assurance test methodologies. The natural space radiation environment is presented, including the contributions of both trapped and transient particles. The effects of shielding on radiation environments are briefly discussed. Laboratory radiation sources used to simulate radiation environments are covered, including how to choose appropriate sources to mimic environments of interest. The fundamental interactions of radiation with materials via direct and indirect ionization are summarized. Some general test considerations are covered, followed by in-depth discussions of physical mechanisms and issues for total dose and single-event effects testing. The purpose of this document is to describe why the test protocols we use are constructed the way they are. In other words, to answer the question: “Why do we test it that way”?

Radiation Effects in Flash Memories

Abstract: We review ionizing radiation effects in Flash memories, the current dominant technology in the commercial non-volatile memory market. A comprehensive discussion of total dose and single event effects results is presented, concerning both floating gate cells and peripheral circuitry. The latest developments, including new findings on the mechanism underlying upsets due to heavy ions and destructive events, are illustrated.

Physics of Multiple-Node Charge Collection and Impacts on Single-Event Characterization and Soft Error Rate Prediction

Abstract: Physical mechanisms of single-event effects that result in multiple-node charge collection or charge sharing are reviewed and summarized. A historical overview of observed circuit responses is given that concentrates mainly on memory circuits. Memory devices with single-node upset mechanisms are shown to exhibit multiple cell upsets, and spatially redundant logic latches are shown to upset when charge is collected on multiple circuit nodes in the latch. Impacts on characterizing these effects in models and ground-based testing are presented. The impact of multiple-node charge collection on soft error rate prediction is also presented and shows that full circuit prediction is not yet well understood. Finally, gaps in research and potential future impacts are identified.

Pulsed-Laser Testing for Single-Event Effects Investigations

Abstract: The application of pulsed lasers to the study of Single-Event Effects (SEEs) in integrated circuits and devices is described. The role of a pulsed laser is to provide spatial and temporal information about SEEs, information that is not available when broad-beam ion sources are used. A detailed description is given of the mechanisms involved, including light propagation and absorption by both linear and non-linear processes. Numerous examples highlight the versatility and usefulness of the technique in the study of SEEs.

Radiation Effects in SiGe Technology

Abstract: Silicon-Germanium (SiGe) technology effectively merges the desirable attributes of conventional silicon-based CMOS manufacturing (high integration levels, at high yield and low cost) with the extreme levels of transistor performance attainable in classical III-V heterojunction bipolar transistors (HBTs). SiGe technology joins together on-die high-speed bandgap-engineered SiGe HBTs with conventional Si CMOS to form SiGe BiCMOS technology, including all the requisite RF passive elements and multi-level thick-Al metalization required for high-speed circuit design. Such an silicon-based integrated circuit technology platform presents designers with an ideal division of labor for realizing optimal solutions to many performance-constrained mixed-signal (analog + digital + RF) systems. The unique bandgap-engineered features of SiGe HBTs enable several key merits with respect to operation across a wide variety of so-called “extreme environments”, potentially with little or no process modification, ultimately providing compelling advantages at the circuit and system level, across a wide class of envisioned commercial and defense applications. Here we give an overview of this interesting field, focusing primarily on the intersection of SiGe HBTs, and circuits built from them, with radiation-intense environments such as space.

An Updated Perspective of Single Event Gate Rupture and Single Event Burnout in Power MOSFETs

Abstract: Studies over the past 25 years have shown that heavy ions can trigger catastrophic failure modes in power MOSFETs [e.g., single-event gate rupture (SEGR) and single-event burnout (SEB)]. In 1996, two papers were published in a special issue of the IEEE Transaction on Nuclear Science [Johnson, Palau, Dachs, Galloway and Schrimpf, “A Review of the Techniques Used for Modeling Single-Event Effects in Power MOSFETs,” IEEE Trans. Nucl. Sci., vol. 43, no. 2, pp. 546-560, April. 1996], [Titus and Wheatley, “Experimental Studies of Single-Event Gate Rupture and Burnout in Vertical Power MOSFETs,” IEEE Trans. Nucl. Sci., vol. 43, no. 2, pp. 533-545, Apr. 1996]. Those two papers continue to provide excellent information and references with regard to SEB and SEGR in vertical planar MOSFETs. This paper provides updated references/information and provides an updated perspective of SEB and SEGR in vertical planar MOSFETs as well as provides references/information to other device types that exhibit SEB and SEGR effects.

Radiation Effects in Advanced Multiple Gate and Silicon-on-Insulator Transistors

Abstract: The aim of this review paper is to describe in a comprehensive manner the current understanding of the radiation response of state-of-the-art Silicon-on-Insulator (SOI) and FinFET CMOS technologies. Total Ionizing Dose (TID) response, heavy-ion microdose effects and single-event effects (SEEs) will be discussed. It is shown that a very high TID tolerance can be achieved by narrow-fin SOI FinFET architectures, while bulk FinFETs may exhibit similar TID response to the planar devices. Due to the vertical nature of FinFETs, a specific heavy-ion response can be obtained, whereby the angle of incidence becomes highly important with respect to the vertical sidewall gates. With respect to SEE, the buried oxide in the SOI FinFETs suppresses the diffusion tails from the charge collection in the substrate compared to the planar bulk FinFET devices. Channel lengths and fin widths are now comparable to, or smaller than the dimensions of the region affected by the single ionizing ions or lasers used in testing. This gives rise to a high degree of sensitivity to individual device parameters and source-drain shunting during ion-beam or laser-beam SEE testing. Simulations are used to illuminate the mechanisms observed in radiation testing and the progress and needs for the numerical modeling/simulation of the radiation response of advanced SOI and FinFET transistors are highlighted.

First Performance Results of Ce:GAGG Scintillation Crystals With Silicon Photomultipliers

Abstract: A new single-crystal Cerium doped Gd3Al2Ga3 O123Al2Ga3 O12 (GAGG) scintillation crystal with high luminosity, high density and relatively fast decay time has successfully been grown. We report on the first performance results of the new GAGG scintillation crystal read out with silicon photomultipliers (SiPM) from Hamamatsu (MPPC) and FBK. The best energy resolution (511 keV peak of Ge-68) of 7.9% was attained with GAGG coupled to MPPC and 9.0% with the FBK SiPM after correcting for non-linearity. On the other hand, the best coincidence resolving time (FWHM) of polished 3 × 3 × 5 mm3 and 3 × 3 × 20mm3crystals were 464 ±12 ps and 577 ±22 ps for GAGG crystals compared to 179 ±8 ps and 214 ±6 ps for LYSO crystals respectively with MPPCs. The rise time of GAGG was measured to be 200 ps (75%) and 6 ns (25%) while the decay time was 140 ns (92%), 500 ns (7.7%) 6000 ns (0.3%).

Radiation Effects on Fiber Gratings

Abstract: Fiber Bragg and long period gratings are photonic components that find numerous applications in telecommunication and sensing. In some cases, such as space, high-energy physics, and nuclear industry, those applications include the presence of ionizing radiation. It is therefore essential to evaluate their radiation response. In this paper, we review radiation effects on various types of fiber gratings.

Fault Simulation and Emulation Tools to Augment Radiation-Hardness Assurance Testing

Abstract: As of 2013, the gold standard for assessing radiation-hardness assurance (RHA) for a system, subsystem, or a component is accelerated radiation testing and/or pulsed laser testing. Fault injection tools, which include both fault simulation and emulation tools, have become more common in the last 15 years. Fault simulation tools use analytical methods for assessing RHA, whereas fault emulation uses hardware methods. Both fault simulation and emulation allow designers to augment traditional RHA techniques to determine whether circuit designs, microarchitectures, components, and application-specific integrated circuits (ASICs) meet the requirements for a particular mission. Fault simulation and emulation can provide the designers the luxury of testing on the benchtop without the time and financial constraints of accelerated radiation testing. This paper explores how to design, implement, and validate a fault simulation or emulation system. The paper ends with several case studies of currently used fault simulation and emulation systems.

Charge Summing in Spectroscopic X-Ray Detectors With High-Z Sensors

Abstract: The spectroscopic performance of photon counting detectors is limited by the effects of charge sharing between neighboring pixels and the emission of characteristic X-rays. For these reasons, an event can be either missed or counted more than once. These effects become more and more of a concern when pixel pitches are reduced, and for the technology available so far, this meant that there would always be a trade-off between a high spatial and a high spectral resolution. In this work, we present first measurements obtained with the new Medipix3RX ASIC, which features a network of charge summing circuits establishing a communication between pixels which helps to mitigate these effects. Combined with cadmium telluride sensors, we show that this new technology is successful at improving a detector's spectroscopic capabilities even at pixel pitches as small as 55 μm. At this pitch, we measure an energy response function similar to that observed for a pixel pitch of 165 μm in the absence of a charge summing circuitry. This amounts to an effective reduction of the pixel area by at least one order of magnitude at a comparable energy response. Additionally, we present synchrotron measurements at high X-ray fluxes, where significant pulse pile-up occurs, and provide first experimental evidence for a net benefit when balancing spectroscopic performance and high flux tolerance in charge summing mode.

Design and Performance of a Resistor Multiplexing Readout Circuit for a SiPM Detector

Abstract: A silicon photomultiplier (SiPM)-based positron emission tomography (PET) detector was developed using a resistor network charge division multiplexing circuit for detector readout. The detector consists of a lutetium-yttrium oxy-orthosilicate (LYSO) scintillation crystal array, an SiPM array detector (SPMArray 4, SensL Inc., Cork, Ireland) and the resistor multiplexing network implemented in a through-hole package to facilitate changing of resistor values. For purposes of optimizing the readout circuit, the LYSO array used was a 4 4 crystal array with crystal size mm on a pitch of 3.37 mm, matched to the SiPM pixel size. Flood image, energy resolution, photopeak amplitude, timing resolution, and signal time-pickoff measurements were performed using standard NIM electronics. The resistor network values were optimized through an iterative process. The performance of the detector was evaluated over a range of temperatures from 23°C to 60°C by heating the detector. The ability of the detector to resolve crystals smaller than the SiPM pixel pitch was evaluated using a dual-layer LYSO array with crystals of 1.67-mm pitch. The optimal resistor network values were found to be 100 Ω along the rows connecting the SiPM pixels and 56 Ω for the columns. For these resistor value settings, the average energy resolution for the central four crystals in the array at 23.5°C was 13.3% ± 0.3% and degraded to 16.3% ± 0.3% at 60°C. The photopeak amplitude decreased by 2%/°C, and the timing resolution degraded from 3.43 ± 0.22 ns to 4.64 ± 0.25 ns for a 350-750-keV energy window over this temperature range. The signal time-pick-off point shifted earlier by 2.7 ns as the temperature increased, an effect likely due to changes in the signal shape with temperature. The detector was able to resolve all 113 crystals in the dual-layer LYSO array. These results demonstrate that the resistor multiplexing readout circuit functions well for reading out SiPM array based detectors, which use scintillator crystal arrays much smaller than the SiPM pixel pitch. The reduced number of output signals achieved through this signal multiplexing greatly reduces the number of signal cables required. In addition, the ability of this detector to function over a wide range of temperatures offers significant flexibility in defining the system operating temperature set point.

Design Techniques for Xilinx Virtex FPGA Configuration Memory Scrubbers

Abstract: SRAM-based FPGAs are in-field reconfigurable an unlimited number of times. This characteristic, together with their high performance and high logic density, proves to be very convenient for a number of ground and space level applications. One drawback of this technology is that it is susceptible to ionizing radiation, and this sensitivity increases with technology scaling. This is a first order concern for applications in harsh radiation environments, and starts to be a concern for high reliability ground applications. Several techniques exist for coping with radiation effects at user application. In order to be effective they need to be complemented with configuration memory scrubbing, which allows error mitigation and prevents failures due to error accumulation. Depending on the radiation environment and on the system dependability requirements, the configuration scrubber design can become more or less complex. This paper classifies and presents current and novel design methodologies and architectures for SRAM-based FPGAs, and in particular for Xilinx Virtex-4QV/5QV, configuration memory scrubbers.

Iterative CT Reconstruction Using Shearlet-Based Regularization

Abstract: Total variation (TV) methods have been proposed to improve the image quality in count-reduced images, by reducing the variation between neighboring pixels. Although very easy to implement and fast to compute, TV-based methods may lead to a loss of texture information when applied to images with complex textures, such as high-resolution abdominal CT images. Here, we investigate the use of another regularization approach in the context of medical images based on multiresolution transformations. One such transformation is the shearlet transform, which is optimally sparse for images that are C2 except for discontinuities along C2 curves, and has better directional sensitivity than most other, related, wavelet transform approaches. We propose to solve the convex problem using the split-Bregman (augmented Lagrangian) approach. One of the primary advantages of the split-Bregman approach, is that the shearlet transform can easily be incorporated into the sparse-view CT reconstruction. The required sparsity prior is the l1 norm of the shearlet coefficients. Results are shown for this method in comparison to the same framework with TV as the regularization term on simulated data. The noise-resolution performance is investigated at different contrast levels. At equal image noise, TV-based regularization outperforms shearlet-based regularization. However, when image texture is analyzed on measured mouse data, shearlets outperform TV, which suffers from staircasing effects. Our results show that there are benefits in using shearlets in CT imaging: texture is reconstructed more accurately compared to when TV is used, without biasing the image towards a piecewise constant image model. However, due to the larger support of the basis functions, our results suggest that uncareful usage of shearlets may lead to wavy artifacts, which can be equally unwanted as staircasing effects.

Proton-Induced Dehydrogenation of Defects in AlGaN/GaN HEMTs

Abstract: The responses to 1.8 MeV proton irradiation of AlGaN/GaN HEMTs grown under Ga-rich and ammonia-rich conditions are investigated in this work. Changes in defect energy distributions of AlGaN/GaN HEMTs during proton irradiation are characterized via temperature-dependent low-frequency noise measurements. Density functional theory calculations show these changes are consistent with the reconfiguration and/or dehydrogenation of oxygen-related defects in Ga-rich devices.

Single-Event Performance and Layout Optimization of Flip-Flops in a 28-nm Bulk Technology

Abstract: Alpha, neutron, and heavy-ion single-event measurements were performed on both high-performance and hardened flip-flop designs in a 28-nm bulk CMOS technology. The experimental results agree very well with simulation predictions and confirm that event error rates can be reduced dramatically using effective layout design.

Radiation Hardness Assurance Testing of Microelectronic Devices and Integrated Circuits: Test Guideline for Proton and Heavy Ion Single-Event Effects

Abstract: This document gives detailed test guidelines for single-event upset (SEU), single-event latchup (SEL), single-event burnout (SEB), and single-event gate rupture (SEGR) hardness assurance testing. It includes guidelines for both heavy-ion and proton environments. The guidelines are based on many years of testing at remote site facilities and our present understanding of the mechanisms for single-event effects.

Development of a Dual-Sided Readout DOI-PET Module Using Large-Area Monolithic MPPC-Arrays

Abstract: We are proposing a novel design for a module with depth of interaction (DOI) capability for gamma rays by measuring the pulse-height ratio of double-sided Multi-Pixel Photon Counters (MPPCs) coupled at both ends of a scintillation crystal block. Thanks to newly developed monolithic MPPC arrays consisting of 4 × 4 channels with a three-side buttable package, the module is very thin and compact, thereby enabling less dead space between each module when arranged into a fully designed gantry. To demonstrate our concept of a DOI measuring technique, we first made a 1-D crystal array consisting of five Ce-doped Gd3Al2Ga3O12 (Ce:GAGG) cubic crystals measuring 3×3×3 mm3 in size, separated by a layer of air approximately 10 μm-thick. When the light signals output from both ends are read with the 3×3 mm2 MPPCs, the position of each crystal is clearly distinguished. The same measurements were also made using Ce-doped (Lu,Y)2(SiO4)O (Ce:LYSO), achieving a similarly good separation. We then fabricated thin Ce:GAGG 2-D crystal arrays consisting of two types: [A] 4 × 4 matrix of 3×3×3 mm3 pixels, and [B] 10 t 10 matrix of 0.8×0.8×5 mm3 pixels, with each pixel divided by a BaSO4 reflector 0.2 mm-thick. Then four arrays are laid on top of each other facing the DOI direction through a layer of air 10 μm-thick. We demonstrated that the 3-D position of each Ce:GAGG pixel is clearly distinguished in both the 2-D and DOI directions for type A and B when illuminated by 662 keV gamma rays. Average energy resolutions of 9.8 ± 0.8% and 11.8 ± 1.3% were obtained for types A and B, respectively. These results suggest that our proposed method is simple and offers promise in achieving both excellent spatial and energy resolutions for future medical imaging, particularly in positron emission tomography (PET).

Combined High Dose and Temperature Radiation Effects on Multimode Silica-Based Optical Fibers

Abstract: We investigate the response of Ge-doped, P-doped, pure-silica, or Fluorine-doped fibers to extreme environments combining doses up to MGy(SiO 2) level of 10 keV X-rays and temperatures between 25 °C and 300 °C. First, we evaluate their potential to serve either as parts of radiation tolerant optical or optoelectronic systems or at the opposite, for the most sensitive ones, as punctual or distributed dosimeters. Second, we improve our knowledge on combined ionizing radiations and temperature (R&T) effects on radiation-induced attenuation (RIA) by measuring the RIA spectra in the ultraviolet and visible domains varying the R&T conditions. Our results reveal the complex response of the tested fibers in such mixed environments. Increasing the temperature of irradiation increases or decreases the RIA values measured at 25 °C or sometimes has no impact at all. Furthermore, R&T effects are time dependent giving an impact of the temperature on RIA that evolves with the time of irradiation. The two observed transient and stationary regimes of temperature influence will make it very difficult to evaluate sensor vulnerability or the efficiency of hardening approaches without extensive test campaigns.

A 19.6 ps, FPGA-Based TDC With Multiple Channels for Open Source Applications

Abstract: This work presents a multi-channel, time-to-digital converter (TDC) based on a field-programmable gate array (FPGA). A thorough characterization of the TDC, based on a Xilinx Virtex-6 FPGA, is presented and several performance parameters are described, including distortions due to the FPGA architecture, temperature effects, intra-chip position variation, and chip-to-chip variation. An optimized TDC exhibits 10 ps LSB duration, an integral non-linearity range of 3.86 LSB, and an input range longer than 100 μs. Total time uncertainty (single-shot jitter) is measured to be 19.6 ps at a time difference of 40 ns, and less than 400 ps at a time difference larger than 100 μs.

High Resolution Photon Counting With MCP-Timepix Quad Parallel Readout Operating at $> 1~{\rm KHz}$ Frame Rates

Abstract: The unique capability of microchannel plates (MCPs) to convert a single photon/ electron/ ion/ neutron into a charge of 104 -107 electrons localized within 4-12 μm from the event position is widely used in event counting imaging detectors. The high spatial and timing resolution of MCP detectors have been demonstrated with different readout techniques. A compromise between the spatial and temporal resolution, the global/local counting rate and active area must always be made for each detector application. In this paper we present a 28 × 28 mm2 MCP detector with 2 × 2 Timepix ASICs for readout, capable of ~ 10 μm spatial resolution at event rates up to ~ 3 MHz, and in excess of 200 MHz with ~ 55 μm pixels. This detector has a unique capability to detect multiple simultaneous events, up to several thousand with ~ 10 μm resolution and > 25000 for the 55 μm mode. The latter is enabled by the new fast readout electronics capable of readout speeds of ~ 1200 frames/sec. Despite its limitations (relatively small active area, readout dead time of 300 μs) the MCP-Timepix detector can be very attractive for applications where high spatial resolution needs to be preserved for nearly simultaneous events, e.g., time of flight measurements with pulsed sources. The low noise of the Timepix readout enables operation at gains as low as 104 -105, which should extend the lifetime of the MCP detectors operating at high counting rates.

High Resolution Gamma Ray Spectroscopy at MHz Counting Rates With LaBr $_{3}$ Scintillators for Fusion Plasma Applications

Abstract: High resolution γ-ray spectroscopy measurements at MHz counting rates were carried out at nuclear accelerators, combining a LaBr 3(Ce) detector with dedicated hardware and software solutions based on digitization and off-line analysis. Spectra were measured at counting rates up to 4 MHz, with little or no degradation of the energy resolution, adopting a pile up rejection algorithm. The reported results represent a step forward towards the final goal of high resolution γ-ray spectroscopy measurements on a burning plasma device.

Development of Double-Sided Full-Passing-Column 3D Sensors at FBK

Abstract: We report on the main design and technological characteristics related to the latest 3D sensor process developments at Fondazione Bruno Kessler (FBK, Trento, Italy). With respect to the previous version of this technology, which involved columnar electrodes of both doping types etched from both wafer sides and stopping at a short distance from the opposite surface, passing-through columns are now available. This feature ensures better performance, but also a higher reproducibility, which is of concern in medium volume productions. In particular, this R&D project was aimed at establishing a suitable technology for the production of 3D pixel sensors to be installed into the ATLAS Insertable B-Layer. An additional benefit is the feasibility of slim edges, which consist of a multiple ohmic column termination with an overall size as low as 100 μm. Eight batches with two different wafer layouts have been fabricated using this approach, and including several design options, among them the ATLAS 3D sensor prototypes compatible with the new read-out chip FE-I4.

Electron-Induced Single-Event Upsets in Static Random Access Memory

Abstract: We present experimental evidence of single-event upsets in 28 and 45 nm CMOS SRAMs produced by single energetic electrons. Upsets are observed within 10% of nominal supply voltage for devices built in the 28 nm technology node. Simulation results provide supporting evidence that upsets are produced by energetic electrons generated by incident X-rays. The observed errors are shown not to be the result of “weak bits” or photocurrents resulting from the collective energy deposition from X-rays. Experimental results are consistent with the bias sensitivity of critical charge for direct ionization effects caused by low-energy protons and muons in these technologies. Monte Carlo simulations show that the contributions of electron-induced SEU to error rates in the GEO environment depend exponentially on critical charge.

An Automated SEU Fault-Injection Method and Tool for HDL-Based Designs

Abstract: Evaluating the sensitivity to soft-errors of integrated circuits and systems became a main issue especially if they are intended to operate in space or at high altitudes. In this paper, a new fully automated SEU fault-injection method is presented and illustrated by its application to an 8051 microcontroller. Predicted SEU error-rates are in a good agreement with results issued from radiation ground testing, thus putting in evidence the accuracy of the studied method.