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Single and multiple-event upsets in \ HfO_2/\ Hf one transistor, one resistor (1T1R) resistive random access memory (RRAM) structures are modeled dynamically using 3-D technology computer-aided design (TCAD) simulations. A dynamic single-event compact model is presented that allows direct correlation of the ion-generated voltage transient across the RRAM and the change in RRAM resistance. Experiments and modeling demonstrate an exponential relationship between the susceptibility of the RRAM and the applied voltage. Two implementations of the model are also presented including hardening voltage-susceptible resistive memory technologies and the impact of highly scaled access transistors. [ABSTRACT FROM PUBLISHER]

Single-event upsets in \bf HfO\bf 2/{\bf Hf} 1T1R Resistive Random Access Memory (RRAM) structures are experimentally demonstrated by generating current transients in the access transistors of the memory cells. The relationship between the single-event upset threshold of the RRAM and the applied voltage is exponential, which is verified using TPA laser analysis and heavy-ion irradiation. Multiple-Event Upsets (MEUs) also occur, where individual ions incrementally change the RRAM’s resistance until their cumulative effect causes an upset. Single-event models are presented that allow direct correlation of the voltage across the RRAM, caused by the ion-generated current transient, and the change in RRAM resistance. The RRAM is vulnerable only in the high resistance state, when a voltage capable of writing to the cell is applied to the bit line. This is approximately 0.5% of the memory element’s operation time, leading to relatively low projected upset rates. [ABSTRACT FROM PUBLISHER]

Charge collection by multiple junctions is investigated using broadbeam heavy-ion and backside laser current transient measurements. The probability that significant charge is collected by more than one junction is greater for laser-generated events compared to heavy-ion measurements, which is attributed to the larger carrier generation track radius for the laser. With both sources, the probability of collecting charge on multiple junctions saturates at high charge generation levels. Effects caused by the interaction between junctions on the transient current waveforms is determined using position-correlated two-photon absorption laser analysis. The total charge collected for ion strikes between four adjacent junctions is shown to be approximately the same as for a direct strikes on a single junction, even though the incident ion does not pass through the depletion region of a biased junction. [ABSTRACT FROM PUBLISHER]

Transient capture measurements on an irradiated diode show the effect of increasing ion LET and varying strike location on transient current response. Significant modulation of the electrostatic potential in the device depletion region during and after the strike profoundly affects transient characteristics. The peak transient current tends to saturate with increasing ionization intensity. The saturation depends on device parameters and the applied bias. A previously developed analytical model is used to describe the mechanisms responsible for this trend. Ion strikes near the device contacts produce transients that are significantly different than strikes away from the contacts, but still in the active region of the device. This is attributed to well potential modulation effects. Device-level simulations, broadbeam heavy-ion measurements, and two-photon absorption single-event effects testing are used to investigate these phenomena. The implications of these results for highly-scaled technologies are also discussed. [ABSTRACT FROM PUBLISHER]

Charge collection measurements reveal that the presence of high-Z materials increases proton-induced charge collection cross sections for high charge collection events. The mechanism for this effect is proton-induced fission events as shown through validated Monte Carlo simulations. These fission fragments are emitted isotropically in contrast to high-LET secondary particles from proton-silicon interactions which tend to be forward directed. [ABSTRACT FROM AUTHOR]

Variability in energy deposition caused by intrinsic statistical fluctuations is quantified for specific radiation environments. Differences in effective flux are observed for minimally ionizing particles, typically leading to a decrease in predicted soft error rate, the magnitude of which depends on the threshold LET. When compared to spectra accounting for energy-deposition fluctuations, predictions with traditional LET spectra in CREME96 are found to lead to conservative estimates in almost all situations. [ABSTRACT FROM AUTHOR]

The single-event-transient response of InGaAs MOSFETs exposed to heavy-ion and laser irradiations is investigated. The large barrier between the gate oxide and semiconductor regions effectively suppresses the gate transients compared with other types of III-V FETs. After the initial radiation-induced pulse, electrons and holes flood into the channel region at short time. The electrons are collected efficiently at the drain. The slower moving holes accumulate in the channel and source access region and modulate the source-channel barrier, which provides a pathway for transient source-to-drain current lasting for a few nanoseconds. The peak drain transient current reaches its maximum when the gate bias is near threshold and decreases considerably toward inversion and slightly toward depletion and accumulation. Two-dimensional TCAD simulations are used to understand the charge collection mechanisms. [ABSTRACT FROM PUBLISHER]

RRAM memory cells demonstrate resilience to ionizing dose and displacement damage, despite the presence of a nonhardened access transistor. Degradation in RRAM performance was not observed until large displacement damage doses and complete functionality was regained by cycling. A significant reduction in both the high and low resistance memory states and a complete collapse of the resistive window was observed for large proton fluences in RRAMs tested. Degradation in resistance states is associated with the generation of additional vacancies, which leads to (an) additional filament(s) in parallel to the existing conductive filament. Additional vacancies from displacement damage in the oxide of the resistive element do not permanently degrade device operation. The low resistance state is recovered to the pre-irradiation resistance through cycling at nominal high-speed switching conditions. Recovery of the resistive window to pre-irradiation values is obtained by applying longer write pulses which migrate remnants of radiation-induced filaments. [ABSTRACT FROM PUBLISHER]

Heavy-ion and two-photon-absorption (TPA) experiments have been performed on ultra-thin implant-free quantum well SiGe channel pMOSFETs. Both the single-event-transient pulse magnitude and polarity can depend strongly on the location of the strike along the device channel. The polarity inversion occurs primarily because very limited transient charge collection occurs below the quantum well, as confirmed by two-dimensional TCAD simulation. [ABSTRACT FROM PUBLISHER]

Charge collection mechanisms in AlGaN/GaN MOS-HEMTs are investigated. Device types include those with no gate oxide, and those with HfO_2 and Al_2O_3 gate oxides. Simultaneous charge collection is observed at the gate and the drain or the source, depending on strike location. Heavy ion data coupled with device simulations show that the introduction of a thin HfO_2 layer in the gate stack introduces only a small valence band barrier, reducing but not preventing collection of holes at the gate in HfO_2-gate devices. Furthermore, using Al_2O_3 gate oxide increases the valence band barrier over that of the HfO_2, to the point where the radiation-induced transient is not detectable. [ABSTRACT FROM PUBLISHER]

This correspondence comments on the correlation between measured and simulated charge collection in two diode structures presented in [1]. In [1], results from pulsed-laser-induced charge deposition via two-photon absorption revealed reasonable correlation between experimental data and simulations in some aspects but showed lack of correlation in terms of the measured and predicted magnitudes of the collected charge. The source of this poor agreement has recently been determined, and is attributed to an incorrect pulse energy calibration used for those experiments. With the proper energy calibration applied, the agreement between simulation and experiment is nearly quantitative for all observables in both devices. These results significantly strengthen the validity of the nonlinear optical beam propagation method numerical approach for accurately predicting pulsed-laser-induced charge deposition. [ABSTRACT FROM PUBLISHER]

Carrier-density distributions generated via two-photon absorption from pulsed laser excitation are simulated using nonlinear-optical beam propagation software. These simulated carrier-density distributions are used to calculate depth profiles of the integrated collected charge using a rectangular-parallel-piped approach for two silicon diodes of different structure. Using a set of proposed correlation metrics, the resulting simulated charge collection profiles are found to exhibit good agreement with measured transient charge-collection data for most, but not all of the metrics. The physical phenomena underlying the correlation metrics are discussed in detail. The remaining discrepancies that exist between the simulated and experimental results are addressed and their potential causes are detailed. [ABSTRACT FROM PUBLISHER]

Measurements of single particle displacement damage are presented as discrete increases in reverse-biased diode leakage current, or current steps, caused by individual heavy ions in ^252Cf-irradiated JFET diodes. The maximum size of measured current steps agrees with calculations obtained from the expression for Shockley-Read-Hall generation when the radiation-induced defect density is derived from Monte Carlo simulations of atomic displacements and the electric field enhancement of defect emission is taken into account. The distribution of the current steps shows good agreement with experimental data. [ABSTRACT FROM PUBLISHER]

A novel “quad-path” radiation hardening technique is implemented in a switched-capacitor sample/hold amplifier and validated by laser testing. The proposed technique eliminates the signal-range limitations of the original dual-path hardening technique by using both n- and p-type switches with separate dual and complementary signal paths. Single-event effect sample errors are reduced by up to 90%, with minimal speed, power and area penalties. [ABSTRACT FROM PUBLISHER]

Single particle displacement damage events are reported in silicon diodes irradiated with ^252Cf and ^241Am. In situ measurements of reverse current show the result of displacement damage incurred from individual fission fragments in ^252Cf irradiated diodes. Discrete increases in reverse current exceeding 20 fA are measured. The increases are temporally correlated with fission fragment-induced ionization events. The ratio of the damage factor associated with fission fragments to the damage factor associated with alpha particles is in good agreement with the ratio of non-ionizing energy loss calculated for fission fragments to NIEL calculated for alpha particles. [ABSTRACT FROM AUTHOR]

Pulse widths of single-event transients produced by alpha particles in a 65-nm bulk CMOS technology are reported. The experimental setup and calibration of the alpha particle experiment is described in detail. A focused-ion beam is also utilized to explore how pulse broadening in the test circuit impacts the alpha particle SET measurements. The results of this work show that alpha particles are able to induce transient signals with a width of about 25 ps in this technology. [ABSTRACT FROM AUTHOR]