Inherent Uncertainty in the Determination of Multiple Event Cross Sections in Radiation Tests

In radiation tests on SRAMs or FPGAs, two or more independent bitflips can be misled with a multiple event if they accidentally occur in neighbor cells. In the past, different tests such as the ``birthday statistics'' have been proposed to estimate the accuracy of the experimental results. In this paper, simple formulae are proposed to determine the expected number of false 2-bit and 3-bit MCUs from the number of bitflips, memory size and the method used to search multiple events. These expressions are validated using Monte Carlo simulations and experimental data. Also, a technique is proposed to refine experimental data and thus partially removing possible false events. Finally, it is demonstrated that there is a physical limit to determine the cross section of memories with arbitrary accuracy from a single experiment

SEU Characterization of Three Successive Generations of COTS SRAMs at Ultralow Bias Voltage to 14.2 MeV Neutrons

This paper presents a SEU sensitivity characterization at ultra-low bias voltage of three generations of COTS SRAMs manufactured in 130 nm, 90 nm and 65 nm CMOS processes. For this purpose, radiation tests with 14.2 MeV neutrons were performed for SRAM power supplies ranging from 0.5 V to 3.15 V. The experimental results yielded clear evidences of the SEU sensitivity increase at very low bias voltages. These results have been cross-checked with predictions issued from the modeling tool MUlti-SCAles Single Event Phenomena Predictive Platform (MUSCA-SEP3). Large-scale SELs and SEFIs, observed in the 90-nm and 130-nm SRAMs respectively, are also presented and discussed

Defining a strategy to perform life-tests with analog devices

Unlike for memory elements inside integrated circuits, scarce life tests have been performed to study single event transients in discrete analog devices. The reason is that life tests require a large amount of samples to be stored for having enough data allowing statistical conclusions and, usually, single event transients are captured by means of oscilloscopes. In this paper, we propose a strategy to carry out life tests in analog voltage comparators by means of digital programmable device that can detect anomalous pulses in the voltage comparator. Besides, the idea on which this kind of tests relies can be extended to be used with other families of analog devices, such as operational amplifiers, voltage references, etc

Statistical Deviations from the Theoretical only-SBU Model to Estimate MCU rates in SRAMs

This paper addresses a well-known problem that occurs when memories are exposed to radiation: the determination if a bitflip is isolated or if it belongs to a multiple event. As it is unusual to know the physical layout of the memory, this paper proposes to evaluate the statistical properties of the sets of corrupted addresses and to compare the results with a mathematical prediction model where all of the events are SBUs. A set of rules easy to implement in common programming languages can be iteratively applied if anomalies are observed, thus yielding a classification of errors quite closer to reality (more than 80% accuracy in our experiments)

Single Event Upsets under 14-MeV Neutrons in a 28-nm SRAM-based FPGA in Static Mode

A sensitivity characterization of a Xilinx Artix-7 FPGA against 14.2 MeV neutrons is presented. The content of the internal SRAMs and flip-flops were downloaded in a PC and compared with a golden version of it. Flipped cells were identified and classified as cells of the configuration RAM, BRAM, or flip-flops. SBUs and MCUs with multiplicities ranging from 2 to 8 were identified using a statistical method. Possible shapes of multiple events are also investigated, showing a trend to follow wordlines. Finally, MUSCA SEP3 was used to make assesment for actual environments and an improvement of SEU injection test is proposed

Single Events in a COTS Soft-Error Free SRAM at Low Bias Voltage Induced by 15-MeV Neutrons

This paper presents an experimental study of the sensitivity to 15-MeV neutrons of Advanced Low Power SRAMs (A-LPSRAM) at low bias voltage little above the threshold value that allows the retention of data. This family of memories is characterized by a 3D structure to minimize the area penalty and to cope with latchups, as well as by the presence of integrated capacitors to hinder the occurrence of single event upsets. In low voltage static tests, classical single event upsets were a minor source of errors, but other unexpected phenomena such as clusters of bitflips and hard errors turned out to be the origin of hundreds of bitflips. Besides, errors were not observed in dynamic tests at nominal voltage. This behavior is clearly different than that of standard bulk CMOS SRAMs, where thousands of errors have been reported

Experimental and Analytical Study of the Responses of Nanoscale Devices to Neutrons Impinging at Various Incident Angles

In harsh radiation environments, it is well known that the angle of incidence of impinging particles against the surface of the operating devices has significant effects on their sensitivity. This article discusses the sensitivity underestimations that are made if particle isotropy is not taken into account, by means of an analytical study made with a single-event upset predictive platform. To achieve this goal, experimental results carried out with a commercial-off-the-shelf (COTS) bulk 130-nm nonvolatile static random access memory (SRAM) for various incident angles on 14.2 MeV neutrons are first discussed. Then, a modeling tool called multiscales single-event phenomena predictive platform (MUSCA-SEP3) is used to predict the sensitivity of this memory under the same environmental conditions. Predictions and experimental results will be cross-checked, and therefore, the feasibility of this tool will be demonstrated for testing any other incident angle. Finally, an isotropic environment and an XY SRAM array will be emulated with MUSCA in order to demonstrate that the asymmetrical cross sections that were observed experimentally for various incidence angles are due to the underlying asymmetry of the metalization/passivation layers within the device with respect to its active silicon. Conclusions will finally be drawn as for the importance of taking into account particle isotropy in radiation-ground tests

Evaluation of a COTS 65-nm SRAM Under 15 MeV Protons and 14 MeV Neutrons at Low VDD

This article presents an experimental study on the sensitivity of a commercial-off-the-shelf (COTS) bulk 65-nm static random access memory (SRAM) under 15.6 MeV proton irradiation when powered up at ultralow bias voltage. Tests were run on standby and while reading the memory. Results show obvious evidence indicating that decreasing the bias voltage below 1 V exponentially increases the number of observed errors. Single-bit upsets (SBUs) and multiple-cell upsets (MCUs) (mostly with vertical shapes according to the manufacturers' layout) are reported and their behavior is analyzed in this article. Predictions on the single-event upset (SEU) sensitivity obtained with the multiscales single-event phenomena predictive platform (MUSCA-SEP3) modeling tool are also provided and compared with the experimental results. These are also compared with 14.2 MeV neutrons, showing a significant difference in the cross sections for both irradiation sources. Total ionizing dose (TID) tests and GEANT4 simulations were also run to check for the reason behind the difference in the cross section between these two particles

Radiation tests on commercial instrumentation amplifiers, analog switches & DAC's

A study of several commercial instrumentation amplifiers (INA110, INA111, INA114, INA116, INA118 & INA121) under neutron and vestigial gamma radiation was done. Some parameters (Gain, input offset voltage, input bias currents) were measured on-line and bandwidth, and slew rate were determined before and after radiation. The results of the testing of some voltage references REF102 and ADR290GR and the DG412 analog switch are shown. Finally, different digital-to-analog converters were tested under radiation

Monocyte chemoattractant protein-1 Is an independent predictor of coronary artery ectasia in patients with acute coronary syndrome

Our purpose was to assess a possible association of inflammatory, lipid and mineral metabolism biomarkers with coronary artery ectasia (CAE) and to determine a possible association of this with acute atherotrombotic events (AAT).We studied 270 patients who underwent coronary angiography during an acute coronary syndrome 6 months before. Plasma levels of several biomarkers were assessed, and patients were followed during a median of 5.35 (3.88–6.65) years. Two interventional cardiologists reviewed the coronary angiograms, diagnosing CAE according to previously published criteria in 23 patients (8.5%). Multivariate binary logistic regression analysis was used to search for independent predictors of CAE. Multivariate analysis revealed that, aside from gender and a diagnosis of dyslipidemia, only monocyte chemoattractant protein-1 (MCP-1) (OR = 2.25, 95%CI = (1.35–3.76) for each increase of 100 pg/mL, p = 0.001) was independent predictor of CAE, whereas mineral metabolism markers or proprotein convertase subtilisin/kexin type 9 were not. Moreover, CAE was a strong predictor of AAT during follow-up after adjustment for other clinically relevant variables (HR = 2.67, 95%CI = (1.22–5.82), p = 0.013). This is the first report showing that MCP-1 is an independent predictor of CAE, suggesting that CAE and coronary artery disease may share pathogenic mechanisms. Furthermore, CAE was associated with an increased incidence of AATThis work was supported by grants from the following: Fondo de Investigaciones Sanitarias (PI05/0451, PI05/1497, PI05/52475, PI05/1043, PS09/01405, and PI10/00072, PI14/01567, PI17/01615): http://www.isciii.es/ISCIII/ es/contenidos/fd-investigacion/fd-financiacion/convocatorias-ayudas-accion-estrategica-salud.shtml; Spanish Society of Cardiology; Spanish Heart Foundation. http://www.secardiologia.es/; Spanish Society of Arteriosclerosis.www.searteriosclerosis.org; CiberCV. http://www.cibercv.es/; RECAVA (RD06/0014/0035); www.recava.com; Fundación Lilly. https://www.lilly.es/nuestra-compania/fundacion-lilly-folder; Instituto de Salud Carlos III FEDER (FJD biobank: RD09/0076/00101); http://www.isciii.es/; and AbbVie Laboratories. http://www.abbvie.es/