Engineering topics
Publications and source records attributed to Edmonds, Larry D..
This paper reports proton damage in LED and phototransistor of the Micropac 66179 optocoupler. Analysis of the test data reveals interesting information, such as the dependence of the transistor gain on irradiation and photocurrent.
A single-event effect (SEE) occurs when a single ionizing particle passing through an electronic device produces a detectable event in the device. The type of SEE most frequently discussed in the literature is a "single-node upset" problem in which an upset at a given node depends only on conditions seen by that node. In contrast, some devices are designed so that an upset becomes a "dual-node" problem in which a device upset depends on conditions simultaneously seen by two nodes. This report derives a method for estimating heavy-ion induced upset rates for the dual-node problem.
The ADC model is a charge-collection model derived for simple p-n junction silicon diodes having a single reverse-biased p-n junction at one end and an ideal substrate contact at the other end. The present paper extends the model to include multiple junctions, and the goal is to estimate how collected charge is shared by the different junctions.
We present a test methodology for estimating system error rates of Field Programmable Gate Arrays (FPGAs) mitigated with Triple Modular Redundancy (TMR). The test methodology is founded in a mathematical model, which is also presented. Accelerator data from 90 nm Xilins Military/Aerospace grade FPGA are shown to fit the model. Fault injection (FI) results are discussed and related to the test data. Design implementation and the corresponding impact of multiple bit upset (MBU) are also discussed.
A previous rigorous mathematical analysis of drift-diffusion equations was used to investigate collected charge in a simple reverse-biased p-n junction diode exposed to an ionization source that liberates carriers (electron-hole pairs) in a quasi-neutral region within the diode. Each of two simple models was found to agree with the more rigorous analysis when carrier liberation is sufficiently intense. One is the sensitive volume (SV) model, and the other was called “ambipolar diffusion with a cutoff” (ADC). The earlier rigorous analysis was worked out in detail only for a localized source, i.e., a point source of carrier liberation, so it was able to validate the applicability of each simple model only for that case. The present paper treats an arbitrary spatial distribution of carrier generation and concludes that the ADC model remains valid for this more general case, but the SV model does
This viewgraph presentation reviews the basics of single event upset mitigation, triple-module redundancy (TMR), new "fitting" equation for TMR, and examples of application to real data.
Charge collection from ion tracks in epi diodes is investigated by computer simulations. As previously noted by others, collected charge can exceed charge liberated in the epi layer. Several cases are compared to illustrate the effect of changing ion LET, epi doping density, and doping types. It is found that the n(sup +)-p-p(sup +) diode displays a funneling regime and a diffusion regime (as previously noted by others),, but the p(sup +)-n-n(sup +) diode does not. Simple models are proposed for quantitative estimates of collected charge. A qualitative two-state picture of funneling is discussed.
Report presents theoretical calculations of contribution of Auger recombination to depletion of charge carriers from ionization track left by passage of energetic heavy ion through silicon-based electronic device.
Upper bounds on rates of single-event upsets (SEU's) in digital integrated circuits and other electronic devices exposed to anisotropic fluxes of energetic ionizing particles computed by use of improved method. Derived from simplified, worst-case mathematical models of charge-collecting volumes and physical phenomena in electronic devices.
Two reports describe preliminary theoretical and experimental studies based on method described in "Laser Scanner Tests For Single-Event Upsets" (NPO-18216). Laser-scan and heavy-ion data found correlated within factor of two. Method of testing for single-event upsets intended to overcome disadvantages of, complement, and/or substitute for more-expensive cyclotron-testing method, which does not provide spatial resolution.
Report discusses collection of electrical charge from track of energetic heavy ion through reverse-biased n+/p junction in semiconductor device. Study focuses on effect of funneling upon total charge collected by low-impedance external circuit. Presents detailed qualitative description of collapse of depletion region and subsequent recovery.
Collection of electric charge carriers from track of energetic ion through silicon electronic device studied using diffusion model representing transport of charge from ion track to sink. Effects of ionizing radiation approximated by simple equations.
Report presents results of experiments where multiple-bit errors were induced in 256-kbit commercial integrated-circuit dynamic random-access memory (DRAM) by variety of normally incident heavy ions. Idea demonstrates utility of DRAM and methods used to analyze experimental data, with view towards applying methods and data to other digital integrated circuits.
Rigorous analysis yields reliable criteria for "best-fit" functions. Improved "curve-fitting" method yields approximate solutions to differential equations of steady-state diffusion. Method applies to problems in which rates of diffusion depend linearly or nonlinearly on concentrations of diffusants, approximate solutions analytic or numerical, and boundary conditions of Dirichlet type, of Neumann type, or mixture of both types. Applied to equations for diffusion of charge carriers in semiconductors in which mobilities and lifetimes of charge carriers depend on concentrations.
The theoretical analysis presented indicates that Auger recombination can reduce charge collection from very dense ion tracks in silicon devices. It is of marginal importance for tracks produced by 270-MeV krypton, and therefore it is of major importance for ions exhibiting a significantly larger loss. The analysis shows that recombination loss is profoundly affected by track diffusion. As the track diffuses, the density and recombination rate decrease so fast that the linear density (number of electron-hole pairs per unit length) approaches a nonzero limiting value as t approaches infinity. Furthermore, the linear density is very nearly equal to this limiting value in a few picoseconds or less. When Auger recombination accompanies charge transport processes that have much longer time scales, it can be simulated by assigning a reduced linear energy transfer to the ion.
A method for constructing upper bound estimates for device single event upset (SEU) rates is presented. A directional Heinrich flux, as a function of direction, must be known. A computer code, included, converts the directional Heinrich flux into an 'effective flux'. The effective flux provides a simple way to estimate upper bound SEU rates for devices with a known normal incident cross section versus LET curve.
Report describes experimental and computer-simulation study of multiple-bit errors caused by impingement of single energetic ions on 256-Kb dynamic random-access memory (DRAM) integrated circuit. Studies illustrate effects of different mechanisms for transport of charge from ion tracks to various elements of integrated circuits. Shows multiple-bit errors occur in two different types of clusters about ion tracks causing them.
Funneling is qualitatively discussed in detail, and a quantitative analysis is given for the total (time-integrated) collected charge. It is shown that, for an n(+)/p junction, the total collected charge QT is given by QT = (1 + mu-n/mu-p) QD + 2Q(diff), where QD is the charge initially liberated in the depletion region and Qdiff is charge collected by diffusion. This equation does not apply to very short ion tracks or to devices having a thin epilayer. A numerical example is presented, and a comparison is made with PISCES results.