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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Response of a DRAM to single-ion tracks of different heavy-ion species and stopping powers

Multiple-bit errors caused by single-ion tracks in a 256-kb DRAM fabricated by a bulk process were observed for different ion species and stopping power values. The results demonstrate the utility of this device for the evaluation of ion-beam uniformity and ion-beam-induced charge collection in IC devices. The data indicate that single-ion-induced charge transport results in multiple-bit error clusters due to lateral diffusion of excess minority carriers (electrons). Charge collection occurred from a depth of up to 35 microns from the surface of the device. An apparent charge loss was observed for very heavy ions with a high stopping power (Au at 350 MeV).

Zoutendyk, J. A.↗
NASA NTRS1987

Response of a metal-oxide-semiconductor field-effect transistor to a cosmic-ray ion track

A cosmic-ray ion track passing perpendicularly through the oxide layer of an enhancement-mode metal-oxide-semiconductor field-effect transistor (MOSFET) forms a conducting path, the resistance of which is proportional to the stopping power of the cosmic ion and independent of the cross-sectional area of the ion track. The voltage across the oxide capacitance may drop below the threshold voltage if the gate bias is sufficiently low or if the external resistance in the gate-source circuit is sufficiently high. The first of a pair of MOSFETs forming a flip-flop circuit may thus be turned off, and the second transitor may turn on, providing it has a sufficiently short delay time, thereby completing a single-event upset.

Benumof, Reuben↗
NASA NTRS2018

Recent Developments in the Code RITRACKS (Relativistic Ion Tracks)

The code RITRACKS (Relativistic Ion Tracks) was developed to simulate detailed stochastic radiation track structures of ions of different types and energies. Many new capabilities were added to the code during the recent years. Several options were added to specify the times at which the tracks appear in the irradiated volume, allowing the simulation of dose-rate effects. The code has been used to simulate energy deposition in several targets: spherical, ellipsoidal and cylindrical. More recently, density changes as well as a spherical shell were implemented for spherical targets, in order to simulate energy deposition in walled tissue equivalent proportional counters. RITRACKS is used as a part of the new program BDSTracks (Biological Damage by Stochastic Tracks) to simulate several types of chromosome aberrations in various irradiation conditions. The simulation of damage to various DNA structures (linear and chromatin fiber) by direct and indirect effects has been improved and is ongoing. Many improvements were also made to the graphic user interface (GUI), including the addition of several labels allowing changes of units. A new GUI has been added to display the electron ejection vectors. The parallel calculation capabilities, notably the pre- and post-simulation processing on Windows and Linux machines have been reviewed to make them more portable between different systems. The calculation part is currently maintained in an Atlassian Stash® repository for code tracking and possibly future collaboration.

Plante, Ianik↗
NASA NTRS1989

Characterization of multiple-bit errors from single-ion tracks in integrated circuits

The spread of charge induced by an ion track in an integrated circuit and its subsequent collection at sensitive nodal junctions can cause multiple-bit errors. The authors have experimentally and analytically investigated this phenomenon using a 256-kb dynamic random-access memory (DRAM). The effects of different charge-transport mechanisms are illustrated, and two classes of ion-track multiple-bit error clusters are identified. It is demonstrated that ion tracks that hit a junction can affect the lateral spread of charge, depending on the nature of the pull-up load on the junction being hit. Ion tracks that do not hit a junction allow the nearly uninhibited lateral spread of charge.

Zoutendyk, J. A.↗
NASA NTRS1992

Collection Of Charge By Diffusion From Ion Track

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.

Edmonds, Larry D.↗
NASA NTRS1988

Lateral charge transport from heavy-ion tracks in integrated circuit chips

A 256K DRAM has been used to study the lateral transport of charge (electron-hole pairs) induced by direct ionization from heavy-ion tracks in an IC. The qualitative charge transport has been simulated using a two-dimensional numerical code in cylindrical coordinates. The experimental bit-map data clearly show the manifestation of lateral charge transport in the creation of adjacent multiple-bit errors from a single heavy-ion track. The heavy-ion data further demonstrate the occurrence of multiple-bit errors from single ion tracks with sufficient stopping power. The qualitative numerical simulation results suggest that electric-field-funnel-aided (drift) collection accounts for single error generated by an ion passing through a charge-collecting junction, while multiple errors from a single ion track are due to lateral diffusion of ion-generated charge.

Zoutendyk, J. A.↗
NASA NTRS1996

The Influence of Spatial Variations of Diffusion Length on Charge Collected by Diffusion from Ion Tracks

Charge collected by diffusion from ion tracks in a semiconductor substrate may be influenced by the substrate diffusion length, which is related to recombination losses. A theoretical analysis shows that, excluding some extreme cases, charge collection is insensitive to spatial variations in the diffusion length funciton, so it is possible to define an effective diffusion length having the property that collected charge can be approximated by assuming a uniform diffusion length equal to this effective value.

SRAMs epi SRAMs ion tracks charge collection↗
NASA NTRS2001

Observations on ion track structure in semiconductors : a phenomenological study

An ion track structure model at the nanometer scale is presented. The model is based on electrostatic principles and is supported by observed experimental results conducted on power MOSFETs. The model predicts the existence of a transient induced electric field following the passage of an energetic heavy ion. There are two segments to the field (a radial and an axial component). It is the interaction of this transient electric field with the local environment that can trigger a catastrophic failure.

SEGR↗
NASA NTRS1978

Ion tracking in an electrostatic potential distribution

An ion tracking system utilizing a single detector was designed to resolve two dimensional potential distributions in a vacuum. The ion detector consisted of a continuous dynode electron multiplier tube mounted behind a series of aperture plates. The detector was located on a track below a wedge shaped structure used to produce the desired potential distribution. A 150 volt electron beam aimed at selected regions, ionized the residual gas in the chamber. The ions were ejected from their source points by electrostatic forces causing them to drift downward toward the detector. Measurements of particle energy, detector position, and entry angle of the incoming particle flux were used to initialize a computer trajectory-tracing program. The program assumes a known theoretically calculated potential distribution near the wedge for computation of particle trajectories, providing a basis for evaluating the data. Special attention was given to characterization of the ion detector.

Ross, D. P.↗
NASA NTRS1991

Charge collected by diffusion from an ion track under mixed boundary conditions

Charge-carrier diffusion from an ion track in a silicon substrate at least a few hundred microns thick is analyzed. The substrate upper surface is treated as reflective except for a small section, intended to represent a reverse-biased junction, which is treated as a sink. Total charge collected by the sink is calculated by assuming transport to be governed by an ambipolar diffusion equation with temporally constant and spatially uniform carrier lifetime and diffusion coefficient. Present results apply to a normally incident track but could easily be generalized to arbitrary track direction. The collected charge is found to depend on track length and on the electrostatic capacitance, rather than the area, of the sink. Theoretical predictions are compared to the results of a numerical simulation called the Poisson and Continuity Equation Solver (PISCES) for three cases and are found to agree within a factor of two in the worst case.

Edmonds, Larry D.↗
NASA NTRS1991

Theoretical prediction of the impact of Auger recombination on charge collection from an ion track

A recombination mechanism that significantly reduces charge collection from very dense ion tracks in silicon devices was postulated by Zoutendyk et al. The theoretical analysis presented here concludes that Auger recombination is such a mechanism and is of marginal importance for higher density tracks produced by 270-MeV krypton, but of major importance for higher density tracks. 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 non-zero limiting value as t yields 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.

Edmonds, Larry D.↗
NASA NTRS1991

Theoretical prediction of the impact of Auger recombination on charge collection from an ion track

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.

Edmonds, Larry D.↗
NASA NTRS1989

Spread Of Charge From Ion Tracks In Integrated Circuits

Single-event upsets (SEU's) propagate to adjacent cells in integrated memory circuits. Findings of experiments in lateral transport of electrical-charge carriers from ion tracks in 256K dynamic randon-access memories (DRAM's). As dimensions of integrated circuits decrease, vulnerability to SEU's increases. Understanding gained enables design of less vulnerable circuits.

Zoutendyk, John A.↗
NASA NTRSDate not supplied

Analytical Calculation of the Energy Deposition Spectrum and Average Dose to A Spherical Target By Ion Tracks at All Impact Parameters

Microdosimetry is used to estimate quality factors for risk assessment in radiation protection [1] and to quantify relative biological effectiveness (RBE) for treatment planning of hadron radiation therapy [2]. Radiation physics has shown that energetic ions deposit energy in a complex manner: the track structure. The Local Effect Model (LEM) [3] is often used as an approximation to describe this complex track structure. We have previously calculated an analytical expression for the dose to a spherical target fully located in the penumbra of an ion track using the LEM [4]. In this work, the calculation has been extended to all impact parameters. Furthermore, using these analytical expressions, it was possible to obtain the theoretical energy deposition spectra to a sphere irradiated uniformly.

I Plante↗