Brian D. Sierawski

Monte Carlo Simulation of Single Event Effects

In this paper, we describe a Monte Carlo approach for estimating the frequency and character of single event effects based on a combination of physical modeling of discrete radiation events, device simulations to estimate charge transport and collection, and circuit simulations to determine the effect of the collected charge. A mathematical analysis of the procedure reveals it to be closely related to the rectangular parallelepiped (RPP) rate prediction method. The results of these simulations show that event-to-event variation may have a significant impact when predicting the single-event rate in advanced spacecraft electronics. Specific criteria for supplementing established RPP-based single event analysis with Monte Carlo computations are discussed.

Impact of Low-Energy Proton Induced Upsets on Test Methods and Rate Predictions

Direct ionization from low energy protons is shown to cause upsets in a 65-nm bulk CMOS SRAM, consistent with results reported for other deep submicron technologies. The experimental data are used to calibrate a Monte Carlo rate prediction model, which is used to evaluate the importance of this upset mechanism in typical space environments. For the ISS orbit and a geosynchronous (worst day) orbit, direct ionization from protons is a major contributor to the total error rate, but for a geosynchronous (solar min) orbit, the proton flux is too low to cause a significant number of events. The implications of these results for hardness assurance are discussed.

Multiple-Bit Upset in 130 nm CMOS Technology

The probability of proton-induced multiple-bit upset (MBU) has increased in highly-scaled technologies because device dimensions are small relative to particle event track size. Both proton-induced single event upset (SEU) and MBU responses have been shown to vary with angle and energy for certain technologies. This work analyzes SEU and MBU in a 130 nm CMOS SRAM in which the single-event response shows a strong dependence on the angle of proton incidence. Current proton testing methods do not account for device orientation relative to the proton beam and, subsequently, error rate prediction assumes no angular dependencies. Proton-induced MBU is expected to increase as integrated circuits continue to scale into the deep sub-micron regime. Consequently, the application of current testing methods will lead to an incorrect prediction of error rates

Impact of Ion Energy and Species on Single Event Effects Analysis

Experimental evidence and Monte-Carlo simulations for several technologies show that accurate SEE response predictions depend on a detailed description of the variability of radiation events (e.g., nuclear reactions), as opposed to the classical single-valued LET parameter. Rate predictions conducted with this simulation framework exhibit excellent agreement with the average observed SEU rate on NASAs MESSENGER mission to Mercury, while a prediction from the traditional IRPP method, which does not include the contribution from ion-ion reactions, falls well below the observed rate. While rate predictions depend on availability of technology information, the approach described here is sufficiently flexible that reasonably accurate results describing the response to irradiation can be obtained even in the absence of detailed information about the device geometry and fabrication process.

Muon-Induced Single Event Upsets in Deep-Submicron Technology

Experimental data are presented that show low-energy muons are able to cause single event upsets in 65 nm, 45 nm, and 40 nm CMOS SRAMs. Energy deposition measurements using a surface barrier detector are presented to characterize the kinetic energy spectra produced by the M20B surface muon beam at TRIUMF. A Geant4 application is used to simulate the beam and estimate the energy spectra incident on the memories. Results indicate that the sensitivity to this mechanism will increase for scaled technologies.

Application of RADSAFE to Model the Single Event Upset Response of a 0.25

The RADSAFE simulation framework is described and applied to model SEU in a 0.25 mum CMOS 4 Mbit SRAM. For this circuit, the RADSAFE approach produces trends similar to those expected from classical rectangular parallelepiped models, but more closely represents the physical mechanisms responsible for SEU in the SRAM circuit.

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Heavy ion cross section data taken from a hardened-by-design circuit are presented which deviate from the traditional single sensitive volume or classical rectangular parallelepiped model of single event upset. TCAD and SPICE analysis demonstrate a SEU mechanism dominated by multiple node charge collection. Monte Carlo simulation is used to model the response and predict an on-orbit error rate.

m CMOS SRAM

A comprehensive mathematical framework is established that encompasses both Monte Carlo single event effects (SEE) rate prediction and analytical approximations based on a single rectangular parallelepiped (RPP). Criteria derived from consideration of multiple devices and technologies are presented that are useful in identifying situations where RPP-model predictions of SEE rates may not be appropriate and should be augmented or replaced by advanced physical modeling.

Monte-Carlo Based On-Orbit Single Event Upset Rate Prediction for a Radiation Hardened by Design Latch

A combination of commercial simulation tools and custom applications utilizing Geant4 physics libraries is used to analyze thermal neutron induced soft error rates in a commercial bulk CMOS SRAM. Detailed descriptions of the sensitive regions based upon technology in computer-aided design calibration are used in conjunction with a physics-based Monte Carlo simulator to predict neutron soft error cross sections that are in good agreement with experimental results

General Framework for Single Event Effects Rate Prediction in Microelectronics

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.