Search

Total-ionizing-dose (TID) effects are investigated in a highly-scaled gate-all-around (GAA) FET technology using Si nanowire channels with a diameter of 8 nm. n- and p-FETs are irradiated up to 300 Mrad(SiO2) and annealed at room temperature. TID effects are negligible up to 10 Mrad(SiO2). At ultrahigh doses, the TID degradation depends on the irradiation bias condition, with more severe effects observed in longer channel devices. The worst case irradiation condition is when positive bias is applied to the gate. Threshold-voltage shifts are caused by H+-driven generation of interface traps at the oxide/channel interface. In contrast, FETs irradiated under negative gate bias are dominated by transconductance loss and increases of low-frequency noise, suggesting the activation of border traps. Enhanced off-leakage current is observed in n-FETs due to charge trapping in shallow-trench isolation, and in p-FETs due to trap-assisted recombination at STI sidewalls and/or spacer dielectrics at drain/bulk junctions. [ABSTRACT FROM AUTHOR]

Total-ionizing-dose (TID) responses are investigated for 3-D-sequentially integrated fully depleted silicon-on-insulator (FD-SOI) MOSFETs. Strong layer-to-layer coupling of TID response is observed. The simultaneous application of positive bias to the gate of the bottom-layer device and negative bias to the top-layer device leads to the maximum enhancement of positive charge trapping in the top-layer device and the intermediate dielectric layer. This enhancement is due to the upward-directed electric field in the intermediate dielectric layer under these bias conditions. In contrast, electrostatic shielding prevents the gate bias of the top-layer device from affecting the response of the bottom-layer device, as confirmed by experiments and technology computer-aided design (TCAD) simulations. Effects of layer-to-layer coupling are less significant for postirradiation-biased annealing. [ABSTRACT FROM AUTHOR]

An overview is presented of displacement damage (DD) effects, total-ionizing-dose (TID) effects, and single-event effects in AlGaN/GaN high electron mobility transistors (HEMTs). High-fluence proton-induced DD creates point defects and impurity complexes at fluences that are comparable to or higher than those encountered in space applications. Defect and impurity dehydrogenation also contributes significantly to the DD/TID response at fluences typical of realistic space environments. The bias applied during irradiation can affect the DD/TID response strongly. Bias stress before irradiation can lead to enhanced proton-induced degradation of AlGaN/GaN HEMTs. Low-frequency noise measurements and density functional calculations provide insight into defect microstructures and energy levels. GaN-based HEMTs can be quite vulnerable to single-event effects in space. Of particular concern is single-event burnout (SEB). The vulnerabilities of GaN-based devices to SEB at voltages below rated limits and significant device-to-device variations in SEB response lead to significant voltage derating for GaN-based power devices in space systems. Developing an improved understanding of the effects of defects and hydrogen on the radiation response of AlGaN/GaN HEMTs can improve the DD/TID response by reducing threshold-voltage shifts and transconductance degradation. Reducing defect densities may also reduce the variation in SEB response, enabling reliable device operation at higher voltages in future space systems. [ABSTRACT FROM AUTHOR]

Total-ionizing-dose (TID) effects are investigated for 22-nm fully-depleted silicon-on-insulator (FDSOI) and 14-nm bulk FinFET charge-trap memory transistors. Electron trapping in the gate dielectric establishes the programmed memory state for both silicon on insulator (SOI) and bulk devices. To first order, ionizing radiation does not interact strongly with programing-induced charges in the gate dielectric for either device type. Hole trapping in the buried oxide dominates the TID response of the 22-nm FDSOI devices. The 14-nm bulk devices with two fins and total effective fin widths of 150 nm are minimally affected by TID, but the subthreshold leakage of devices with 40 fins and total effective fin widths of $3~\mu \text{m}$ increases with increasing TID. When devices are programmed or reprogrammed after irradiation, significant increases in subthreshold slope are observed due to the generation of interface traps, border traps, and/or charge lateral nonuniformities. [ABSTRACT FROM AUTHOR]

Total-ionizing-dose (TID) effects and low-frequency noise are evaluated in advanced bulk nMOS and pMOS FinFETs with SiO2/HfO2 gate dielectrics. Otherwise identical devices built with and without through-silicon via (TSV) integration exhibit threshold voltage shifts of less than 25 mV and changes in maximum transconductance of less than 1% up to 2 Mrad(SiO2). TSV integration negligibly impacts threshold shifts and degradation of subthreshold swing and $I_{\mathrm{\scriptscriptstyle ON}}/I_{\mathrm{\scriptscriptstyle OFF}}$ ratios. Similar low-frequency noise magnitudes and frequency dependencies are observed before and after TID irradiation for each device type. Effective densities of the near-interfacial electron traps responsible for the noise in the nMOS devices increase as the surface potential moves toward midgap, while effective densities of the hole traps that cause the noise in the pMOS devices increase as the surface potential moves toward the valence band edge. [ABSTRACT FROM AUTHOR]

Single-event upsets are observed in a 72-layer 3-D NAND flash memory operated in a single-level cell mode after low-energy proton (500 keV–1.2 MeV) and heavy-ion irradiation. The layer-by-layer error count is analyzed to visualize the stopping of low-energy protons within the memory stack, and Monte Carlo simulations are correlated with the experimental data. Direct ionization by low-energy protons is identified by 3-D data analysis and the energy dependence of device-sensitive cross section. Heavy-ion data is also presented for comparison. [ABSTRACT FROM AUTHOR]

Total-ionizing-dose (TID) effects are compared in 1) conventional high-temperature processed planar fully-depleted silicon-on-insulator (FD-SOI) p-channel MOSFETs, 2) 3-D sequentially integrated (3DSI) FD-SOI MOSFETs in the bottom layer with additional thermal budget and process flows due to the creation of the top layer, and 3) 3DSI low-temperature-processed FD-SOI MOSFETs in the top layer. When irradiated under worst case negative bias, 3DSI bottom-isolated transistors show significantly enhanced charge trapping and transconductance degradation than planar devices. The enhanced degradation for bottom-isolated devices is attributed primarily to increased interface- and border-trap formation at the buried oxide (BOX)/Si interface and/or lateral charge nonuniformities in the BOX. The radiation-induced transconductance degradation in top-isolated devices is attributed to the increased resistance of the portion of the channel that underlies the source/drain spacers. [ABSTRACT FROM AUTHOR]

Pulsed-laser-induced single-event current measurements on two geometries of waveguide-integrated germanium photodiodes were conducted over a range of operating voltages to examine the impact of photodiode geometry on the transient response. Vertical p-i-n photodiodes exhibit transients with a duration that is relatively independent of the operating voltage, while the transient duration in lateral p-i-n photodiodes depends on the operating voltage. Furthermore, the experimental measurements facilitate identification of device dimensions that impact the transient response. These results can be used to identify potential radiation mitigation strategies for photodiodes operating in a radiation environment. Understanding the implications of design choices is critical for designing integrated photonic systems that balance system performance with tolerance for radiation degradation. [ABSTRACT FROM AUTHOR]

Semiconductor–insulator interfaces play an important role in the reliability of integrated devices; however, the impact of these interfaces on the physical mechanisms related to single-event effects has not been previously reported. We present experimental data that demonstrate that single-event charge collection can be impacted by changes in interface quality. The experimental data, combined with simulations, show that single-event response may depend on surface recombination at interface defects. The effect depends on strike location and increases with increasing linear energy transfer (LET). Surface recombination can affect single-event charge collection for interfaces with a surface recombination velocity (SRV) of 1000 cm/s and is a dominant charge collection mechanism with SRV $> 10^{5}$ cm/s. [ABSTRACT FROM AUTHOR]

The total-ionizing-dose (TID) response of indium gallium arsenide (InGaAs) MOSFETs with Al2O3 gate dielectrics and several channel lengths is evaluated under different biases. DC static characteristics show large negative threshold voltage Vth shifts and subthreshold stretchout (SS), indicating net positive charge trapping in the gate oxide and generation of the interface and border traps. Hysteresis and Id – Vgs measurements from cryogenic to high temperatures show the important role of defects in the Al2O3 gate dielectric to the TID response. Radiation-induced-hole trapping is attributed to oxygen vacancies in the Al2O3. The relatively large hysteresis in these devices is attributed primarily to dangling Al bonds in the near-interfacial Al2O3. Analysis of the temperature dependence of Vth and SS suggests that the rate at which electrons leave the Al2O3 during a positive-to-negative gate-bias sweep is higher than the rate at which they enter during a negative-to-positive gate-bias sweep. [ABSTRACT FROM AUTHOR]

The onset of ion-induced reverse leakage current in SiC Schottky diodes is shown to depend on material properties, ion linear energy transfer (LET), and bias during irradiation, but not the voltage rating of the parts. This is demonstrated experimentally for devices from multiple manufacturers with voltage ratings from 600 to 1700 V. Using a device with a higher breakdown voltage than required in the application does not provide increased robustness related to leakage current degradation, compared to using a device with a lower voltage rating. [ABSTRACT FROM AUTHOR]

We evaluate the total ionizing dose (TID) responses of InGaAs nMOS FinFETs with different gate lengths irradiated with 10-keV X-rays under different gate biases. The largest degradation after irradiation occurs at $V_{\mathrm {G}} = -1$ V. Radiation-induced trapped positive charge dominates the TID response of InGaAs FinFET transistors, consistent with previous results for InGaAs multifin capacitors. Shorter gate-length devices show larger radiation-induced charge trapping than longer gate-length devices, most likely due to the electrostatic effects of trapped charge in the surrounding SiO2 isolation and SiO2/Si3N4 spacer oxides. The 1/ $f$ noise measurements indicate a high trap density and a nonuniform defect-energy distribution, consistent with a strong variation of effective border-trap density with surface potential. [ABSTRACT FROM AUTHOR]

The total-ionizing-dose response of few layer MoS2 transistors with ZrO2 or h-BN gate dielectrics is investigated under various bias conditions. Defects in MoS2 and surrounding dielectric layers significantly affect radiation-induced trapping. For devices with ZrO2 dielectrics, much larger negative Vth shifts and peak transconductance degradation are observed for irradiation under negative and ground bias than under positive bias. The h-BN devices exhibit positive threshold voltage shifts under negative-bias irradiation. For both ZrO2 and h-BN passivated devices, the peak transconductance degradation results from charge trapping at the surface of the MoS2 or in nearby oxides. Changes in defect energy distributions of MoS2 FETs during X-ray irradiation are characterized via temperature-dependent low-frequency noise measurements. Density functional theory calculations are performed to provide insight into the pertinent defects. [ABSTRACT FROM AUTHOR]

Irradiation of 2N5339 n-p-n bipolar junction transistors (BJTs) with either 250-MeV protons or 10-keV X-rays shifts the input characteristics to lower values of $V_{\mathrm {BE}}$ while degrading the current gain and drive current. The degradation is consistent with increased recombination in the neutral base and emitter–base (E–B) depletion region. A decrease in collector current following proton irradiation suggests that recombination in the neutral base is significant. At a given ionizing dose, degradation is worse for proton irradiation than for X-ray irradiation due to the presence of displacement damage and a higher charge yield. A comparison of degradation produced by the two radiation sources suggests that ~40% of the excess base current resulting from 250-MeV proton irradiation is due to ionization damage. When compared with previous results for other devices, these results suggest that ionization-to-displacement damage ratios in bipolar devices may increase with proton energy in a way that is consistent with trends in charge yield and non-ionizing energy loss (NIEL). [ABSTRACT FROM AUTHOR]

Tunneling-dominated charge transport is demonstrated in vertically stacked MoS2/interlayer/MoS2 heterostructures with Al2O3, hexagonal boron nitride (h-BN), and HfO2 dielectrics. All devices are highly resistant to 10-keV X-ray irradiation. Only small transient changes in X-ray-induced photocurrent are observed as a result of trap creation in the thin interlayer dielectric, with rapid passivation. Samples with Al2O3 and h-BN interlayer dielectrics show significant increases in conduction current during proton irradiation, due to displacement-damage-induced defects that lower the effective tunnel-barrier height. Density-functional-theory calculations provide insights into the pertinent defects. Devices with HfO2 interlayer dielectrics show great promise for use in radiation tolerant, ultimately scaled tunnel FETs. [ABSTRACT FROM AUTHOR]

Lighter doping, pretreatment (exposure to hydrogen in a steam bath), and lower dose rate are each found to exacerbate 10-keV X-ray-induced negative frequency shifts and increase in resistivity measured in T-shaped, asymmetric, piezoresistive, micromachined, and resonating cantilevers. All devices recover to levels close to preirradiation after several hours of postirradiation annealing. The effects are attributed to dose-rate-dependent efficiencies of the depassivation of dopants by hydrogen and surface charging effects, which alter the effective Young’s modulus and shear elastic constants. Increases in resistivity are attributed to increases in scattering causing decreases in mobility. Results indicate the need to consider dopant type and concentration when choosing microelectromechanical systems for use in radiation environments in addition to accounting for low-dose-rate effects. [ABSTRACT FROM AUTHOR]

Significant threshold voltage $V_{\mathrm {th}}$ shifts are observed during 10-keV X-ray irradiation of AlGaN/GaN high-electron mobility transistors (HEMTs). Shifts are much smaller for lower dose-rate Cs-137 irradiation than that for higher dose-rate X-ray irradiation. This occurs because hydrogen transport and interactions with defects and impurities in these crystalline wide bandgap semiconductor materials differ fundamentally from those in amorphous SiO2. The electric field is also higher in GaN-based HEMTs than in bipolar base oxides. The absence of enhanced low-dose-rate sensitivity in these devices simplifies testing of GaN-based HEMTs for space applications. No significant X-ray-induced $V_{\mathrm {th}}$ shifts are observed in development stage InAlN/GaN HEMTs. [ABSTRACT FROM AUTHOR]

The radiation response of complementary metal–oxide–semiconductor (CMOS) gate oxides is typically insensitive to true dose-rate effects, but damage in deep-sub-micrometer technologies is dominated by ionization mechanisms in thick isolation oxides surrounding the transistors. Recent results in 65-nm FETs demonstrated that performance degradation in ultrahigh total ionizing dose (TID) experiments is due to defects in the isolation shallow trench isolation oxide or in the materials composing the lightly doped drain spacers. These insulators are thick, deposited, and crossed by a low electric field, characteristics similar to those typical of passivation oxides in linear bipolar technologies for which an enhanced low-dose-rate sensitivity (ELDRS) has been observed and systematically studied. We report in this paper the clear evidence of a dose-rate sensitivity of the TID-induced damage in both 130- and 65-nm CMOS technologies exposed to different radiation sources (X-rays and $\gamma $ -rays from a 60Co source). This sensitivity is attributed to mechanisms similar to those explaining ELDRS in bipolar devices and represents a significant challenge to the definition of a qualification procedure for circuits to be used in extreme radiation environments. [ABSTRACT FROM AUTHOR]

We demonstrate the utility of focused, pulsed X-rays for investigating localized total ionizing dose effects in bipolar analog integrated circuits. Using the LM139 comparator as a test vehicle, we show how the technique can be used to identify the sources of degradation as a result of irradiating different transistors of the device and how this impacts the input bias current, input offset voltage, and output voltage. The 2-D mapping of the sensitive regions of transistors is presented, where the results of localized irradiation impact the monitored operational parameters. [ABSTRACT FROM PUBLISHER]

The single-event-transient response of InGaAs FinFETs with different fin widths is examined using pulsed-laser and heavy-ion irradiation. Devices with wider fins collect more charge in both environments. Quantum-well structures confine charge collection in the channel, and determine the sensitive volume. Simulations show that the charge density produced by irradiation is similar for devices with different fin widths, but more charge is collected by wider fin devices due to the larger channel volume. Charge accumulated in the buffer and substrate layers modulates the body potential, altering the degree of back-gate control, leading to additional effects associated with charge accumulation in wider fin devices. Optical simulations for a model system suggest that optical phenomena in the fins should be considered for laser testing. These include optical interference, plasmonic enhancement at the metal–dielectric interfaces, and enhanced electron–hole pair recombination due to multiple reflections in multigate devices with nanoscale dimensions. [ABSTRACT FROM PUBLISHER]

A bipolar-transistor-based sensor technique has been used to compare silicon displacement damage from known and unknown neutron energy spectra generated in nuclear reactor and high-energy-density physics environments. The technique has been shown to yield 1-MeV(Si) equivalent neutron fluence measurements comparable to traditional neutron activation dosimetry. This paper significantly extends previous results by evaluating three types of bipolar devices utilized as displacement damage sensors at a nuclear research reactor and at a Pelletron particle accelerator. Ionizing dose effects are compensated for via comparisons with 10-keV X-ray and/or cobalt-60 gamma ray irradiations. Nonionizing energy loss calculations adequately approximate the correlations between particle and device responses and provide evidence for the use of one particle type to screen the sensitivity of the other. [ABSTRACT FROM PUBLISHER]

Nb2O5-based metal–insulator–metal (MIM) diodes are ideal for neuromorphic computing applications because they exhibit desirable rectification, hysteresis, and capacitance characteristics without electroforming. We employ capacitance-frequency measurements to evaluate the total-ionizing-dose res- ponse of these devices to avoid measurement-induced disturbance of trap distributions caused by typical gate-voltage sweeping methods. Power-law dependences are observed for the low-frequency capacitance and conductance, consistent with hopping conduction of carriers through the oxides. Despite their high oxygen-vacancy densities, the Nb2O5-based MIM diodes are radiation tolerant up to at least Mrad(SiO2) doses. [ABSTRACT FROM PUBLISHER]

The degradation induced by ultrahigh total ionizing dose in 65-nm MOS transistors is strongly gate-length dependent. The current drive decreases during irradiation, and the threshold voltage often shifts significantly during irradiation and/or high-temperature annealing, depending on transistor polarity, applied field, and irradiation/annealing temperature. Ionization in the spacer oxide and overlying silicon nitride layers above the lightly doped drain extensions leads to charge buildup as well as the ionization and/or release of hydrogen. Charge trapped in the spacer oxide or at its interface modifies the parasitic series resistance, reducing the drive current. The released hydrogen transports as H+ with an activation energy of ~0.92 eV. If the direction of the electric field is suitable, the H+ can reach the gate oxide interface and depassivate Si-H bonds, leading to threshold voltage shifts. Newly created interface traps are most prominent near the source or drain. The resulting transistor responses and defect-energy distributions often vary strongly in space and energy as a result, as demonstrated through current–voltage, charge-pumping, and low-frequency noise measurements. [ABSTRACT FROM PUBLISHER]

Total-ionizing-dose-induced resonance frequency shifts in piezoresistive micromachined cantilevers are experimentally shown to be dose-rate dependent. Devices were irradiated to 1 Mrad(SiO2) at rates from 5.4 to 30.3 krad(SiO2)/min, with lower rate exposures producing up to four-times more negative frequency shifts than higher rate exposures. Devices that were hydrogenated in a steam bath for 1 h showed shifts similar to those of control (not hydrogenated) devices at higher dose rates, and larger shifts than control devices at lower rates. All devices recovered to levels close to preirradiation after several hours of post-irradiation annealing. The dose-rate dependence is attributed to differences in carrier concentration caused by varying efficiencies of the depassivation of boron by hydrogen at higher and lower dose rates and/or surface charging effects, and the subsequent differences in Young’s modulus that occur as a result. Many of these processes are similar to effects that lead to ELDRS in linear bipolar transistors, emphasizing the need to include low-dose-rate testing of microelectromechanical systems devices when considering them for use in space systems. [ABSTRACT FROM PUBLISHER]

The response of silicon-based microelectromechanical systems resonators to proton irradiation is determined by the combined effects of displacement damage and total ionizing dose (TID). Displacement damage (DD) can lead to carrier removal, which tends to decrease the carrier concentration, and TID leads to dopant activation and/or surface charging effects, which tend to increase the carrier concentration. These competing effects lead to changes in carrier concentration that alter Young’s modulus, and consequently the resonance frequency. For higher flux 2-MeV proton irradiation to 1014/cm2, TID effects dominate at low fluence, leading to a decrease in resonance frequency, which is offset by displacement damage effects at higher fluence. Fast recovery is observed as TID effects anneal out and DD effects remain. For lower-flux 0.8-MeV proton irradiation to 7 \times 10^12 /cm2, DD effects are relatively more significant than for 2-MeV proton irradiation, and an increase in resonance frequency is observed at all fluences. Stopping and range of ions in matter calculations reinforce these conclusions. [ABSTRACT FROM PUBLISHER]

Heavy-ion-induced degradation in the reverse leakage current of SiC Schottky power diodes exhibits a strong dependence on the ion angle of incidence. This effect is studied experimentally for several different bias voltages applied during heavy-ion exposure. In addition, TCAD simulations are used to give insight on the physical mechanisms involved. [ABSTRACT FROM PUBLISHER]

The influence of surface carrier concentration on the ideality factor of excess base current ( \Delta IB ) in gated lateral PNP (GLPNP) bipolar junction transistors (BJTs) induced by 1-MeV electrons is investigated. \Delta IB in LPNP BJTs is impacted by the surface carrier density and radiation-induced interface traps. In GLPNP BJTs, the surface carrier concentration can be controlled by the voltage applied to a gate over the base region. The ideality factor changes after irradiation, and its dependence on emitter-base voltage ( V\mathrm {EB} ) is a function of gate voltage. For the irradiated devices, as the gate voltage decreases from +20 to −5 V, the ideality factor for excess base current changes from a single slope to two-slope behavior. The majority carrier concentration at the surface of the base, controlled by the gate voltage, impacts the excess base current and its ideality factor. [ABSTRACT FROM AUTHOR]

We have characterized the total ionizing dose response of strained Ge p MOS FinFETs built on bulk Si using a fin replacement process. Devices irradiated to 1.0 Mrad(SiO2) show minimal transconductance degradation (less than 5%), very small \text {V}_{th} shifts (less than 40 mV in magnitude) and very little ON/OFF current ratio degradation (<5%), and only modest variation in radiation response with transistor geometry (typically less than normal part-to-part variation). Both before and after irradiation, the performance of these strained Ge p$ MOS FinFETs is far superior to that of past generations of planar Ge $p$ MOS devices. These improved properties result from significant improvements in processing technology, as well as the enhanced gate control provided by the strained Ge FinFET technology. [ABSTRACT FROM PUBLISHER]

We find that the low-frequency 1/ f noise of AlGaN/GaN HEMTs before and after 1.8-MeV proton irradiation is more consistent with a carrier-number fluctuation model that includes a non-constant defect-energy distribution {D}_{t} ( {E}_{f} ) than with the Hooge mobility fluctuation model. A strongly varying Dt ( {E}f ) in these devices is confirmed by measurements of the voltage and temperature dependence of the noise. First-order estimates of effective border-trap density before and after 1.8-MeV proton irradiation are obtained for commercial and research-grade devices using a simple number-fluctuation model. The input-referred noise magnitude of GaN/AlGaN HEMTs decreases at biases that are much more positive than threshold because the gated region of the HEMT comprises a relatively small portion of the channel, and the noise is attenuated by the voltage divider formed by the gated and ungated regions of the channel. [ABSTRACT FROM PUBLISHER]

We evaluate the response of T-shaped, asymmetric, piezoresistive, micromachined cantilevers fabricated on p-type Si to 10-keV X-ray irradiation. The resonant frequency decreases by 25 ppm at 2.1 Mrad(SiO2), and partially recovers during post-irradiation annealing. An explanation of the results is proposed that is based on radiation-induced acceptor depassivation. This occurs because radiation-generated holes release hydrogen from previously passivated acceptors, causing the carrier concentration to increase, especially near the surface. Increased carrier concentration decreases Young’s modulus, resulting in a decrease in the cantilever resonant frequency. Finite element simulations show that the effect of a decreasing Young’s modulus in the surface region is consistent with the measured decrease in resonant frequency in the irradiated devices. [ABSTRACT FROM PUBLISHER]

Total-ionizing-dose (TID) effects on piezoelectric micromachined ultrasonic transducers (pMUTs) are investigated using 10-keV X-rays under different bias conditions. The corresponding changes in resonant frequency and quality factor are evaluated using impedance analysis methods. Radiation-generated electrons or holes are trapped in the pre-existing defects of piezoelectric materials. Therefore, the sensitivity of pMUTs to X-ray irradiation depends strongly on the device bias during irradiation. The trapped charges change stress and strain in the materials due to the inverse piezoelectric effect, resulting in resonant frequency shifts and quality factor variation. [ABSTRACT FROM PUBLISHER]

Responses to 1.8 MeV proton irradiation and 10-keV X-ray irradiation under typical bias conditions are investigated for AlGaN/GaN HEMTs fabricated with different types of process technologies. We find that, in contrast to previous generations of process technologies, total ionizing dose effects can be significant in these devices. For proton irradiation, worst-case bias for transconductance degradation for GaN-on-SiC substrate devices is ON bias, and for devices built on free-standing GaN substrates, the worst-case bias condition is semi-ON bias. Low-frequency noise measurements demonstrate that these differences result from differences in defect types and energy distributions for the different types of devices, both before and after irradiation. These results emphasize the need to test devices under a wide range of conditions during characterization and qualification testing. [ABSTRACT FROM PUBLISHER]

The effects of total-ionizing-dose irradiation are investigated in HfO2/InGaAs quantum-well MOSFETs. Radiation-induced hole trapping is higher for irradiation under positive gate bias than under negative gate bias. Electrical stress-induced electron trapping compensates radiation-induced hole trapping during positive gate-bias irradiation. Stress-induced hole trapping adds to the effects of radiation-induced hole trapping under negative gate bias. Radiation-induced charge trapping increases with the channel length. [ABSTRACT FROM PUBLISHER]

Experimental results on ion-induced leakage current increase in 4H-SiC Schottky power diodes are presented. Monte Carlo and TCAD simulations show that degradation is due to the synergy between applied bias and ion energy deposition. This degradation is possibly related to thermal spot annealing at the metal semiconductor interface. This thermal annealing leads to an inhomogeneity of the Schottky barrier that could be responsible for the increase leakage current as a function of fluence. [ABSTRACT FROM PUBLISHER]

The total ionizing dose response of Ge channel pFETs with raised Si0.55Ge0.45 source/drain is investigated under different radiation bias conditions. Threshold-voltage shifts and transconductance degradation are noticeable only for negative-bias (on state) irradiation, and are mainly due to negative bias-temperature instability (NBTI). Nonmonotonic leakage changes during irradiation are observed, which are attributed to the competition of radiation-induced field transistor leakage and S/D junction leakage. [ABSTRACT FROM PUBLISHER]

A probabilistic Bayesian modeling method for determining the effects of radiation-induced component-level parameter shifts on system-level performance is described. The modeling method incorporates information about the system design and component-level degradation into a Bayesian network and performs inference on the constructed network using Markov chain Monte Carlo approaches, producing distributions for the range of component responses. Deterministic simulations use the results of the Bayesian inference to determine the combined impact of multiple degraded components on system performance quantities. The goal of the modeling approach is to turn uncertain information into actionable knowledge. The utility of this approach is demonstrated using a case study based on total ionizing dose degradation of line-sensor components in a simple line-tracking robot system. [ABSTRACT FROM PUBLISHER]

The sensitivity of GaN/AlGaN HEMTs to 1.8 MeV proton irradiation is greatly enhanced by biasing the devices during irradiation and/or applying high field stress before irradiation. The resulting defect energy distributions are evaluated after irradiation and/or high field stress via low-frequency noise measurements. Significant increases are observed in acceptor densities for defects with \sim 0.2 and \sim 0.7 eV energy levels. These defects appear to dominate the degradation in threshold voltage and transconductance for these devices. Density functional theory (DFT) calculations show that N vacancy-related defects in GaN and hydrogenated ON complexes in AlGaN are strong candidates for the defects with \sim 0.2 eV energy levels in these devices. We also present evidence that the previously unidentified \sim 0.7 eV defect in GaN is a N anti-site defect (NGa). [ABSTRACT FROM PUBLISHER]

NPN and PNP bipolar junction transistors of varying sizes are irradiated with 4-MeV protons and 10-keV X-rays to determine the amount of ionization-related degradation caused by protons and calculate an improved estimate of displacement-related degradation due to protons. While different ratios of degradation produced by displacement damage and ionization effects will occur for different device technologies, this general approach, with suitable margin, can be used as a screen for sensitivity to neutron-induced displacement damage. Further calculations are performed to estimate the amount of degradation produced by 1-MeV equivalent neutron displacement damage compared to that produced by the displacement damage due to protons. The results are compared to previous work. [ABSTRACT FROM PUBLISHER]

The effects of proton-induced displacement damage in GaN HEMTs on circuit-level RF power amplifier parameters such as circuit gain, stability, and RF output power are presented. The results are explained based on the device-level degradation. Commercial-off-the-shelf GaN HEMTs from two manufacturers were compared. Differences are observed in both device and circuit level responses. Suggestions to mitigate the negative effects of displacement damage on GaN based amplifiers are also provided. [ABSTRACT FROM PUBLISHER]

Density functional theory (DFT) has emerged as a powerful tool to model defect properties and dynamics at the quantum mechanical level. Results from targeted DFT calculations can provide valuable insight into the atomistic nature of radiation-induced defect phenomena in microelectronics. This review describes the foundations of DFT, its implementations, and defect calculations. Illustrative examples from recent studies are presented in which DFT calculations, combined with experiments, have led to new insights into the microscopic processes that lead to the observed radiation response. These include GaN/AlGaN HEMTs, proton-induced interface-trap formation at the Si-SiO_2 interface, and the role of hydrogen in enhanced low-dose-rate sensitivity (ELDRS) in bipolar devices and ICs. [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]

MRED is a Python-language scriptable computer application that simulates radiation transport. It is the computational engine for the on-line tool CRÈME-MC. MRED is based on c++ code from Geant4 with additional Fortran components to simulate electron transport and nuclear reactions with high precision. We provide a detailed description of the structure of MRED and the implementation of the simulation of physical processes used to simulate radiation effects in electronic devices and circuits. Extensive discussion and references are provided that illustrate the validation of models used to implement specific simulations of relevant physical processes. Several applications of MRED are summarized that demonstrate its ability to predict and describe basic physical phenomena associated with irradiation of electronic circuits and devices. These include effects from single particle radiation (including both direct ionization and indirect ionization effects), dose enhancement effects, and displacement damage effects. MRED simulations have also helped to identify new single event upset mechanisms not previously observed by experiment, but since confirmed, including upsets due to muons and energetic electrons. [ABSTRACT FROM AUTHOR]

The impact of high-Z metals on energy deposition in thin volumes due to direct ionization by ions in space environments is examined. The importance of energy loss straggling in small volumes typical of those found in advanced devices is also evaluated. It is found that direct ionization by protons over a large energy range may contribute significantly to error rates in advanced silicon on insulator devices due to energy loss straggling. This improves on conventional event rate analysis based on linear energy transfer, which does not describe the contributions of direct ionization by protons to the error rate. [ABSTRACT FROM AUTHOR]

A new geometry-aware single-event enabled compact model for sub-50 nm partially depleted silicon-on-insulator MOSFETs is presented. The model extends the bias-dependent single-event modeling methods with an integrated parasitic BJT using the SPICE Gummel Poon equations and parameters derived from the manufacturer’s process design kit, physical layout, and technology information. The model compares well with TCAD and test data. [ABSTRACT FROM AUTHOR]

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]

Electrical stress and 10-keV x-ray irradiation and annealing responses are evaluated for back-gate MoS2 transistors. Relative stability of device characteristics is observed for constant-voltage stress. The drain current decreases significantly after both positive and negative bias irradiation. Density functional theory calculations and ozone exposure experiments suggest that O atoms adsorbed on the MoS2 surface during 10-keV x-ray irradiation function as electron traps, causing mobility degradation and voltage shifts. [ABSTRACT FROM PUBLISHER]

AlGaN/GaN high electron mobility transistors (HEMTs) irradiated with 1.8-MeV protons show more relative degradation in RF power/current gain, cutoff frequency f_T, and maximum oscillation frequency fmax than DC transconductance. These result from radiation-induced increases in fast bulk and surface trap densities, as well as increasing impedance mismatch at high frequencies with increasing proton fluence. NH3-rich MBE devices show less degradation in DC transconductance, but more degradation in RF gain than Ga-rich devices. [ABSTRACT FROM PUBLISHER]

The total ionizing dose (TID) response of double-gate SiGe-SiO_2/HfO_2 \ pMOS FinFET devices is investigated under different device bias conditions. Negative bias irradiation leads to the worst-case degradation due to increased hole trapping in the HfO_2 layer, in contrast to what is typically observed for devices with SiO_2 or HfO_2 gate dielectrics. This occurs in the devices because radiation-induced holes that are generated in the SiO_2 interfacial layer can transport and become trapped in the HfO_2 under negative bias, leading to a more negative threshold voltage shift than observed at 0 V bias. Similarly, radiation-induced electrons that are generated in the SiO_2 interfacial layer can transport into the HfO_2 and become trapped under positive bias, leading to a more positive threshold voltage shift than observed at 0 V bias. [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]

The total-dose radiation tolerance of 32-nm nFETs is investigated. nFETs built in 32-nm RF-CMOS-on-SOI technology with high-k dielectrics show increased off-state leakage current and electron trapping in the gate oxide. The impact of CMOS-on-SOI technology scaling (from 65-nm to 32-nm) on the total-dose radiation tolerance and hot-carrier reliability (HCR) is investigated through both experiments and supporting TCAD simulations. The 32-nm nFETs exhibit less total-dose degradation compared to 45-nm nFETs. However, the hot-carrier degradation increases as the technology scales. An interplay of electric-field in the gate oxide and impact ionization in the channel region is responsible for the observed differences in the degradation mechanisms for the three technologies. [ABSTRACT FROM AUTHOR]