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1. IntroductionMeasured X-ray powder diffraction line profiles are affected by the geometry of the diffractometer, the shape of the X-ray emission spectrum and the physical characteristics of the sample as [...]

1. IntroductionThe laboratory X-ray powder diffractometer offers several virtues that have rendered it a principal characterization device providing critical data for a range of technical disciplines involving crystalline materials. A [...]

Device-level current transients are induced by injecting carriers using two-photon absorption from a subbandgap pulsed laser and recorded using wideband transmission and measurement equipment. These transients exhibit three distinct temporal trends that depend on laser pulse energy as well as the transverse and vertical charge generation location. The nature of the current transient is controlled by both the behavior of the subcollector-substrate junction and isolation biasing. However, substrate potential modulation, due to deformation of the subcollector-substrate depletion region, is the dominant mechanism affecting transient characteristics. Index Terms--Current transient, electrostatic potential modulation, SiGe HBT, two-photon absorption.

The effects of device orientation on heavy ion-induced multiple-bit upset (MBU) in 65 nm SRAMs are examined. The MBU response is shown to depend on the orientation of the device during irradiation. The response depends on the direction of the incident ion to the n- and p-wells of the SRAM. The MBU response is simulated using Monte Carlo methods for a space environment. The probability is calculated for event size. Single-bit upsets in the space environment account for 90% of all events with exponentially decreasing probabilities of larger MBU events. Index Terms--Multiple-bit upset, MBU, MCU, SEU, heavy ion, SRAM, MRED, GEANT4, soft error.

Monte-Carlo radiation transport code is coupled with SPICE circuit level simulation to identify regions of single event upset vulnerability in an SEU hardened flip-flop, as well as predict single event upset cross sections and on-orbit soft error rates under static and dynamic operating conditions. Index Terms--Geant4, MRED, rate prediction, SEU, SPICE.

As integrated circuits become smaller and more complex, it has become increasingly difficult to simulate their responses to radiation. The distance and time scales of relevance extend over orders of magnitude, requiring a multi-scale, hierarchical simulation approach. This paper demonstrates the use of multi-scale simulations to examine two radiation-related problems: enhanced low-dose-rate sensitivity (ELDRS) in bipolar transistors and single-event effects (SEE) in CMOS integrated circuits. Examples are included that demonstrate how information can be passed from simulation tools operating at one level of abstraction to those operating at higher levels, while maintaining accuracy and gaining insight. Index Terms--Integrated circuits, multi-scale simulation, radiation, single-event effects, total ionizing dose.

1. IntroductionIn the early 1990s, a crystal diffraction instrument was developed at the National Institute of Standards and Technology (NIST) for the accurate comparison of crystal lattice spacing values. The [...]

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. Index Terms--Geant4, MRED, rate prediction, SEU.

Proton-induced energy deposition in a silicon P-i-N focal plane array is analyzed with Monte Carlo based simulations. These simulations include all physical processes, including events resulting from multiple particles incident on a single pixel, to describe the experimental data accurately. Post-processing of Monte Carlo simulations is done to account for the effects of pile up (multiple hits on a single pixel during one integration time) and non-radiation-induced noise in experiment. The results are compared with experimental data, and demonstrate how direct ionization dominates the cross section, yet fluctuations in dE/dx cause a broad range of energy depositions not addressed by an average LET calculation. An event rate is predicted for a full space proton flux and the dominance of direct ionization is shown and compared to computation using constant LET methods in CREME96. This comparison shows that at lower energies, CREME96 sufficiently predicts the event rate, but at higher energies a high fidelity simulation method is needed to capture the distribution. Index Terms--Energy deposited, event rate, focal plane array, Geant4, Monte Carlo, pile up.

This work draws on experimental and simulation results to derive a generalized SEU response model for bulk SiGe HBTs. The model was validated using published heavy ion and new proton data gathered from high-speed HBT digital logic integrated circuits fabricated in the IBM 5AM SiGe BiCMOS process. Calibrating to heavy ion data was sufficient to reproduce the proton data without further adjustment. The validated model is used to calculate upset event rates for low-earth and geosynchronous orbits under typical conditions. Index Terms--Deep trench isolation, Geant4, geosynchronous orbit, low-earth orbit, rate prediction, silicon-germanium HBT, single-event upset.

The RADSAFE simulation framework is described and applied to model SEU in a 0.25 [micro]m 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. Index Terms--GEANT4, heavy-ion, RADSAFE, SEU, TCAD.

Simulation results for the full galactic cosmic ray environment demonstrate that current accelerator-based test methods using linear energy transfer as the engineering metric to characterize single event effects are not sufficient to capture the nuclear reaction portion of the response. Nuclear reactions contribute significantly to on-orbit single-event rates as compared to those from direct ionization induced by the primary ions. Based on these results, the applicability of current single-event test methods to predicting on-orbit event rates is examined and improved procedures are identified. For devices with critical charge values that are in the range where nuclear reactions may play a role in determining the event rate, ground-based tests should include irradiation with several types of ions of different energies to identify the contribution of these reactions to the measured SEE cross section. Index Terms--Nuclear reactions, single event effect rate, single event effects.

Delayed charge collection from ionizing events outside the deep trench can increase the SEU cross section in deep trench isolation technologies. Microbeam test data and device simulations demonstrate how this adverse effect can be mitigated through substrate engineering techniques. The addition of a heavily doped p-type charge-blocking buried layer in the substrate can reduce the delayed charge collection from events that occur outside the deep trench isolation by almost an order of magnitude, implying an approximately comparable reduction in the SEU cross section. Index Terms--Deep trench isolation, Ion Beam Induced Charge Collection (IBICC), silicon germanium, Single Event Upset (SEU), substrate engineering.

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. Index Terms--Energy deposition cross section, multiple-bit upset (MBU), MRED, single event upset (SEU), SRAM, proton effects.

We present measurements of proton-induced single event transients in ultra-low noise HgCdTe IR detector arrays being developed for space-based astronomy and compare to modeling results. Index Terms--HgCdTe, IR detectors, single event transients, space-based astronomy, transient noise.

Simulations show that neglecting ion-ion interaction processes (both particles having Z > 1) results in an underestimation of the total on-orbit single event upset error rate by more than two orders of magnitude for certain technologies. The inclusion of ion-ion nuclear reactions leads to dramatically different SEU error rates for CMOS devices containing high Z materials compared with direct ionization by the primary ion alone. Device geometry and material composition have a dramatic effect on charge deposition in small sensitive volumes for the spectrum of ion energies found in space, compared with the limited range of energies typical of ground tests. Index Terms--Charge deposition, Geant4, heavy ion, MRED, single-event upset (SEU), SEU error rate.

Heavy ion irradiation was simulated using a Geant4 based Monte-Carlo transport code. Electronic and nuclear physics were used to generate statistical profiles of charge deposition in the sensitive volume of an SEU hardened SRAM. Simulation results show that materials external to the sensitive volume can affect the experimentally measured cross-section curve. Index Terms--Cross section, Geant4, MRED, single event upset.

A new software module adding screened Coulomb scattering to the Monte Carlo radiation simulation code Geant4 has been applied to compute the nonionizing component of energy deposited in semiconductor materials by energetic protons and other forms of radiation. This method makes it possible to create three-dimensional maps of nonionizing energy deposition from all radiation sources in structures with complex compositions and geometries. Essential aspects of previous NIEL computations are confirmed, and issues are addressed both about the generality of NIEL and the ability of beam experiments to simulate the space environment with high fidelity, particularly for light ion irradiation at very high energy. A comparison of the displacement energy deposited by electromagnetic and hadronic interactions of a proton beam with published data on GaAs LED degradation supports the conclusion of previous authors that swift light ions and slower heavy ions produce electrically active defects with differing efficiencies. These results emphasize that, for devices with extremely small dimensions, it is increasingly difficult to predict the response of components in space without the assistance of computational modeling. Index Terms--Computational physics, displacement damage, GaAs, Geant4, Monte Carlo, NIEL, nonionizing energy loss, nuclear stopping.