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Irradiation of semiconductors by energetic beams generates excess electrons and holes and may cause device degradation or failure. Both gradual degradation by total ionizing radiation (TID) and sudden degradation/failure (soft/hard breakdown) by a combination of energetic heavy ions and high voltages (typically single-event effects or SEEs) are mediated by excess carriers. The role of defect dynamics in TID degradation has been adequately understood by a combination of experiments and density-functional-theory (DFT) quantum calculations, but little has been done so far to document a role for ion-induced defects in SEE. Here, we report proof-of-principle DFT calculations in a model cubic GaN system for two defect-related excess-carrier phenomena that can play a role in various forms of device degradation and failure. The first phenomenon is the existence, dynamics, and potential roles of defect-induced quasi-localized "resonant states" in the energy-band continua. These states can enhance TID-excess-carrier and hot-carrier degradation. Furthermore, they evolve and multiply during energetic-ion-induced atom recoils and defect creation (displacement damage) and can potentially serve as excess-carrier conduction paths in SEE. The second phenomenon is the conversion of isolated vacancies into nanovoids that can participate in the formation of conducting defect "nanowires" dressed by resonances or in explosive SEE hard breakdowns. [ABSTRACT FROM AUTHOR]

A computationally efficient approach for estimating the impact of a 3-D distribution of carriers on an optical signal propagating within a waveguide is outlined and incorporated into a carrier transport solver to model the optical response as the carriers diffuse within the waveguide. It is shown that as the ionizing particle passes though the waveguide, the transmission will sharply drop, partially recover on the order of picoseconds, and then continue to recover as carriers recombine or escape the waveguide. The transient optical responses of a photonic waveguide can be incorporated into a photonic integrated circuit solver to demonstrate the spatial sensitivity of the radiation-induced transient optical response of a Mach–Zehnder modulator. The impact of the initial distribution of carriers injected into a photonic waveguide during single-event effects (SEEs) testing on the transient optical response is examined to assess the impact of using alternative SEE testing techniques to emulate ionizing particles. Since the transient optical response will depend on both the peak carrier density and total carriers injected into a waveguide, testing with larger carrier distributions will have difficultly matching both the transmission drop and recovery. Due to the reliance on carrier distributions with a larger spatial extent and fewer peak carrier densities than an ionizing particle, care must be taken when using alternative SEE testing techniques to not overestimate the SEE susceptibility of the photonic devices. [ABSTRACT FROM AUTHOR]

Charge transport mechanisms of forward and reverse leakage currents in vertical GaN Schottky barrier diodes are investigated by measuring the temperature-dependent current–voltage characteristics. The results show that the leakage current is primarily governed by dislocation-associated thermionic field emission (TFE). The primary transport path is the reduced, localized conduction band around the dislocation core rather than the continuum defect states. A refined phenomenological physical model is developed for conductive dislocations in GaN, emphasizing that: 1) surface donors, surrounding the core of dislocations, can significantly shrink the barrier region after ionization, causing severe TFE leakage; 2) the ON donors likely to be responsible for TFE have a typical density of ~ 1 × 1018 cm−3 at 300 K and activation energy of 78 meV; and 3) the barrier height at donor sites is ~0.65 eV at 300 K, which is reduced by ~0.4 eV with respect to the dislocation-free region. [ABSTRACT FROM AUTHOR]

Pulsed, laser-induced, single-event current measurements on silicon-on-insulator (SOI) FinFETs at subbandgap wavelength (1260 nm) are affected by the polarization of the laser light used in the experimental testing setup. Such polarization dependence is not observed during pulsed laser, single-event effects testing on large-area silicon diodes, suggesting that polarization dependence arises due to the presence of the nanoscale fin. Plasmonic enhancement is proposed as a likely mechanism for the polarization effects due to the metal/dielectric interfaces in the fin region. The observed polarization dependence has ramifications for collection and interpretation of data acquired by pulsed laser testing. Device orientation of FinFETs and other nanoscale devices during pulsed laser testing should be considered in order to ensure consistent testing conditions and reproducible measurement results across multiple measurement campaigns. [ABSTRACT FROM AUTHOR]

This paper discusses two different modes of breakdown in the reverse-biased I–V characteristics observed generically in bipolar junction transistors (BJTs) with the base emitter shorted, showing an erratic behavior, in the presence of large displacement currents. Experimental observations related to reverse-biased collector junctions of BJTs, that exhibit two different states of breakdown when a fast voltage ramp is applied are presented. Numerical simulations of the transient behavior of avalanche injection in p/n-/n+ structures show that two very close breakdown states coexist. The mechanisms leading to the erratic behavior of the second breakdown are discussed. The jittery nature of the breakdown is attributed to the delay associated with the buildup of the electric field across the n-/n+ junction. [ABSTRACT FROM AUTHOR]

Presents information on a study which derived theoretical expressions which relate to the terminal characteristics of photoconductive switches to the incident light. General relations from energy considerations useful for computation of the efficiency of a variety of switching devices; Measurement of the spatial photosensitivity of a high-resistivity intrinsic substrate with blocking and injecting contacts; Experimental arrangement.

A marked state dependence and significant reduction in SEU cross section with even small increases in incident angle are reported in an asymmetric RC-hardened 90 nm CMOS SRAM. The effects are attributable to the bias dependence and high aspect ratio of the deep trench capacitor sidewall depletion region, exacerbated by process-induced boron depletion. The asymmetric implementation, using capacitive hardening in only one leg of the SRAM cell, led to the appearance of the effect in experimental results. [ABSTRACT FROM PUBLISHER]

The effects of shallow-trench-isolation-induced mechanical stress on radiation-induced off-state leakage current are reported in 90-nm NMOS devices. The radiation-induced leakage current increases with increasing active device-to-isolation spacing. The leakage current also depends on channel width; narrow devices exhibit less leakage before irradiation, but more after irradiation. These geometrical factors affect the mechanical stress in the device, which impact the dopant diffusion and activation and the charge trapping in the STI oxide. The combined effects of these layout-related phenomena affect the sensitivity to radiation-induced charge. [ABSTRACT FROM AUTHOR]

Complex interplay between hydrogen-related defect formation and passivation is observed in irradiated bipolar transistors. Hydrogen soaking experiments are performed to evaluate the dependence of defect buildup and annealing in gated lateral bipolar transistors on hydrogen exposure. Comparisons of the radiation responses of transistors tested in 2009 to identical devices from the same wafer tested in 2003 show that aging has reduced the amount of radiation-induced interface trap and oxide trapped charge formation in most cases. These results demonstrate that the way in which the radiation response of a hydrogen-sensitive device evolves with age depends on whether hydrogen is diffusing into or out of the device, and whether the initial defect concentration favors passivation or depassivation reactions. These results strongly suggest that hydrogen exposure cannot replace low-dose-rate irradiation in ELDRS tests for bipolar devices and ICs without extensive characterization testing. [ABSTRACT FROM AUTHOR]

Enhanced Low Dose Rate Sensitivity (ELDRS) in bipolar linear transistors was first identified in bipolar micro-circuit transistors in 1991 and demonstrated in bipolar linear circuits in 1994. Since then it has been a major topic of research, characterization and analysis. Data compendia of low dose rate enhancement factors were presented in 1996, 2001 and 2008, identifying 30 unique widely used circuit types as susceptible to ELDRS. Early work on ELDRS was directed toward identifying mechanisms, characterizing circuits and developing hardness assurance methods, concentrating on accelerated testing techniques. More recently the research on ELDRS has focused on the effects of pre-irradiation elevated temperature stress (PETS), final passivation layers and molecular hydrogen in the package. This review paper provides an update on ELDRS in bipolar linear circuits, including the most recent results of mechanisms research, and the effects of post metallization processing on the total ionizing dose response. [ABSTRACT FROM AUTHOR]

We present evidence that enhanced low-dose-rate sensitivity (ELDRS) in lateral and substrate pnp bipolar devices can occur because of the much lower probability for electron capture by protons in SiO2, as compared to mobile or trapped holes. New experimental results and a critical evaluation of previous work demonstrate that, at high dose rates and/or in oxides with low concentrations of hydrogen, electrons can more easily neutralize slowly diffusing or metastably trapped holes via annihilation (recombination) or compensation (offsetting trapping) before the holes can release H+. In contrast, at low dose rates and/or in oxides with higher concentrations of hydrogen, which can react with and modify the structure of O-vacancy-related defects, it is more likely that holes can release H+ during transport. This is because the cross section for electron capture by H+ is several orders of magnitude smaller than the electron capture cross section for a slowly moving or metastably trapped hole. This enhanced proton release at low dose rates or in oxides with high hydrogen concentrations can lead to increased interface trap formation, which is the most common source of enhanced gain degradation in lateral and substrate pnp bipolar transistors. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

Heavy ion-induced single events transients (SETs) in advanced digital circuits are becoming a significant reliability issue for space-based systems. In this work, two experiments are performed on devices designed to look specifically at digital single event transients. Small voltage variations, like those that can be found across an integrated circuit, are shown to affect the digital single event transient response significantly. For technologies with supply voltages near 1 V, these potential variations may result in unexpected vulnerability. [ABSTRACT FROM AUTHOR]

Radiation-induced dopant passivation is evidenced for the first time in partially-depleted SOI n-channel MOSFETs. Isochronal annealing experiments following 10 Mrad(SiO2) irradiation demonstrate that the neutralization of boron atoms in the NMOSFET body is most pronounced in the 125°C-150°C temperature range. This results in an abrupt decrease of the threshold voltage and the subthreshold swing, due to the transition of the body from partial to full depletion. The SO! four-gate transistor, inherently present in the partially-depleted MOSFET structure, is demonstrated to be a very efficient tool for monitoring dopant neutralization through irradiation and annealing. Radiation-induced dopant passivation has important consequences regarding the reliability of short-channel partially-depleted NMOSFETs. [ABSTRACT FROM AUTHOR]

Abstract: The single-event error rate in advanced semiconductor technologies can be estimated more accurately than conventional methods by using simulation based on accurate descriptions of a large number of individual particle interactions. The results can be used to select the ion types and energies for accelerator testing and to identify situations in which nuclear reactions will contribute to the error rate. [Copyright &y& Elsevier]

Degradation due to irradiation is known to be associated with the presence of hydrogen in the bulk of the gate oxide, in bulk Si, and at the Si/SiO2 interface. Previous studies have shown that the migration of protons in the oxide for positive applied gate bias and their reactions at the interface can account for the time and dose-rate dependence of the degradation. Recent experiments, however, have shown that interfacial degradation can occur even in the presence of strong negative gate bias that prevents the arrival of protons at the interface from the oxide side. This result suggests that mechanisms in addition to proton drift in SiO2 can lead to radiation-induced interface-trap formation. Since previous work on modeling the enhanced low-dose-rate sensitivity (ELDRS) of irradiated bipolar devices was based on formation of an electrostatic barrier that hinders proton transport to the interface at high dose rates, this effect also must be examined in more detail. In this work we use results from first-principles calculations to demonstrate that hydrogen can also be released easily in bulk Si, and especially in the near interfacial area. This hydrogen moves readily to the interface under negative bias. Typical hydrogen precursors in Si are identified as H-dopant complexes. ELDRS shares thus a common origin with another critical reliability phenomenon, the negative bias-temperature instability. [ABSTRACT FROM AUTHOR]

Total dose effects on silicon on insulator (SOI) UNI BOND wafers are studied via optical second harmonic generation (SHG). This technique is qualitatively compared with the pseudo-MOSFET technique for monitoring charges at the interfaces. optical and electrical methods are combined to separate the contribution of the signal from each interface to the total SHG intensity. Radiation-induced oxide and interface traps increase the interface fields as determined from the SHG signals and the results are compared with electrical measurements. [ABSTRACT FROM AUTHOR]

The radiation effects community has long known that single event transients in digital microcircuits will have an increasing importance on error rates as device sizes shrink. However separating these errors from static errors in latch cells has often proved difficult. Thus determining both the significance and the nature of these transient errors has not been easy. In this study, by utilizing a latch that is radiation hard at static clock frequencies the errors due to transients could be separated. By separating the transient error rate from the static upset error rate, the pulse structure of the propagating transients was studied using SPICE. The implications of these pulsewidths will also be discussed. [ABSTRACT FROM AUTHOR]

Structures integrated onto a BiCMOS test chip are specially designed to characterize the complex mechanisms related to proton radiation response in bipolar technologies. Bipolar devices from a commercial process are modified to include independent gate terminals. Through the use of gate control, the effects of proton-induced defects on discrete bipolar devices and analog bipolar circuits can be analyzed independently, thereby facilitating a quantitative description of the nonlinear relationship between the radiation defects and electrical response at both the device and circuit level. [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]

Gallium oxide is an emerging wide-bandgap semiconductor with promise for applications in space systems that may be exposed to energetic particles. We use molecular dynamics simulations, based on first principles density-functional methods, to determine the nature and stability of the defects generated by atoms knocked-out by particle irradiation at near threshold energies (found to be 28 ± 1 eV for Ga and 14 ± 1 eV for O). For Ga atoms, several types of low energy knock-out events result in defect complexes, but the final structures depend critically on the initial displacement direction. In contrast, a vacancy plus a peroxide linkage occurs in all types of low energy knock-out events of O atoms. Based on energy-barrier calculations, there is a low (high) probability for Ga (O) defect recombination. The electronic structure of residual, relaxed defects generated by Ga knock-outs reveals defect levels near the band edges. [ABSTRACT FROM AUTHOR]

Total-ionizing-dose (TID) effects and low-frequency noise are evaluated in 30-nm gate-length bulk and silicon-on-insulator (SOI) FinFETs for devices with fin widths of 10–40 nm. Minimal threshold voltage shifts are observed at 2 Mrad(SiO2), but large increases in low-frequency noise are found, and significant changes in defect-energy distributions are inferred. Radiation-induced leakage current is enhanced for narrow- and short-channel bulk FinFETs. Short-channel SOI FinFETs show enhanced degradation compared with longer-channel devices. Narrow- and short-channel SOI devices exhibit high radiation tolerance. Significant random telegraph noise (RTN) is observed in smaller devices due to prominent individual defects. [ABSTRACT FROM AUTHOR]

We evaluate the total-ionizing-dose (TID) responses of InGaAs nMOS fin field-effect transistors (FinFETs) with a modified gate-stack irradiated with 10-keV X-rays under different gate biases. This modified InGaAs nMOS FinFET process shows decreased subthreshold leakage current and increased hysteresis in as-processed devices, and reduced hole trapping in irradiated devices, than first-generation development-stage devices. The reduction in subthreshold leakage current is attributed to changing the buffer layer from GaAs to In0.3Ga0.7As, thereby enhancing the material quality. Both the increased hysteresis in as-processed devices and reduced hole trapping in irradiated devices are attributed primarily to thinning the Al2O3 layer that separates the HfO2 from the InGaAs layers. This facilitates charge exchange with defects at the HfO2/Al2O3 interface and reduces the percentage of radiation-induced holes that are generated in Al2O3 and trapped in HfO2. The removal of a tungsten layer above the TiN gate reduces the interface dose enhancement. [ABSTRACT FROM AUTHOR]

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]

This paper models the indeterminacy that occurs during the formation of breakdown current channels in a bipolar structure, when subjected to an ultrafast high voltage pulse. The experimental results, pertaining to different regimes of the voltage ramp speed, applied across the bipolar structure are modeled. The avalanche injection mechanisms under variable high speed ramps are studied through the formation and propagation of ionizing waves, which lead to either weak or strong injection of mobile carriers, as the high current injection paths get coupled. Furthermore, the role of emitter injection is related to the indeterminacy associated with the snapback phenomenon and systematically related to the experimental observations. [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]

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]

Energetic carriers in semiconductors thermalize by impact-ionization, which generates electron–hole pairs (EHPs), and by energy losses to phonons. The average EHP creation energy is typically about three times the energy gap. In 1960, Shockley derived a simple equation for the average EHP creation energy with a single free parameter that fits experimental values for a wide range of materials, but the underlying assumptions, as stated, have been widely criticized as lacking justification. Modified expressions derived by improved approximations have been proposed but do not fare better. Here, we revisit the foundations of Shockley's equation and provide a robust justification for the kinetic-energy component as a model averaging procedure and then apply a similar procedure to the phonon component of the equation. The phonon result retains Shockley's form, but the interpretation and justification are now on par with those of the kinetic-energy term. The single-parameter fit to the data remains unchanged, i.e., the present analysis accounts for the exceptional applicability of Shockley's equation. [ABSTRACT FROM AUTHOR]

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]

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]

A method of analyzing ion-induced reverse leakage current in SiC power devices is described. The resulting methodology enables the estimation of the proportion of ion strikes that produce step increases in leakage current as well as distributions of sensitive die areas relative to leakage step magnitude. These results are compared across various bias and ion linear energy transfer combinations to isolate the influence of each variable. [ABSTRACT FROM AUTHOR]

Negative-bias-stress and total-ionizing-dose (TID) effects in deeply scaled Ge-gate-all-around (GAA) nanowire (NW) devices are characterized for different biasing conditions. Negative-bias-stress-induced degradation in Ge GAA device originates primarily from the interface- and border-trap generation. Devices stressed at high gate voltage show rapid initial degradation and quick saturation dominated by interface-trap generation. Radiation-induced OFF-state leakage current in Ge GAA NWs increases with dose due to enhanced band-to-band tunneling (BTBT) caused by charge trapping in the shallow trench isolation (STI). [ABSTRACT FROM AUTHOR]

Gallium nitride (GaN) has attracted great attention as a structural material for advanced microelectromechanical systems (MEMS), thanks to its excellent ensemble of electrical and mechanical properties. Here, we report on studying the effects of ion radiation-induced displacement damage on resonant MEMS made of GaN film grown on aluminum nitride (AlN) buffer layer. We design and fabricate GaN/AlN heterostructure doubly-clamped microstring resonators with length $L \,\, =100$ , 200, 300, 400, 500, 600, and 700 $\mu \text{m}$ , and irradiate the devices with 440-keV Ar $^{+}$ ions, to probe the effects of ion radiation-induced displacement damage on the resonance behavior. The ion energy and range have been selected so that the ions would stop within the GaN layer, thus allowing diagnostics to show the effects of damage in the structure. The multimode resonance frequencies of the devices decrease significantly ($\vert \Delta f\vert /f >50$ %) with the increase of fluence beyond 1014 cm−2. According to scanning electron microscopy (SEM) imaging, the irradiated GaN/AlN resonators are visibly deformed at high fluence, where the amount of curvature increases monotonically with the fluence. The deformation of the structures can be ascribed to the change in both Young’s modulus and built-in stress resulting from ion radiation-induced displacement damage. The results extend the understanding of radiation-induced damage mechanisms in resonant MEMS. [ABSTRACT FROM AUTHOR]

Total-ionizing-dose effects are evaluated in vertical-charge-trapping NAND devices with silicon oxynitride (SiON) and SiO2 tunneling layers. Processing splits include SiON tunneling layers with and without H2/D2 high-pressure annealing. Programmed devices were irradiated to 500 krad(SiO2) with 10-keV X-rays and annealed for 30 min. Second programming after annealing does not fully restore the original, programmed state. Radiation-induced trapped holes compensate for deeply trapped electrons that are injected into the dielectric during device programming. Throughout the full irradiation and annealing sequence, threshold voltages remain large enough to enable successful nonvolatile (NV) memory application. [ABSTRACT FROM AUTHOR]

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]

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 model for radiation-induced interface-trap buildup distinguishes among the contributions of hydrogen dimerization, electron recombination, and electric field mechanisms, quantitatively explaining time-dependent and true dose rate effects in irradiated bipolar isolation oxides. Hydrogen dimerization is the dominant ELDRS mechanism for devices exposed to medium \ H2 concentrations (1% per volume), whereas \ H2 cracking dominates as \ H2 concentration is increased further. Electron recombination mechanisms contribute at high dose rates (> 100~\ rad(\ SiO2)/{\ {s}}), but are not the dominant ELDRS mechanism at dose rates lower than 100 \ rad(\ SiO2)/{\ {s}}). [ABSTRACT FROM AUTHOR]

Abstract: The impact of device width on the variability of radiation-induced leakage currents in 90nm and 65nm CMOS technologies is investigated. The off-state leakage current variability increases with decreasing channel width for both technologies, and with increasing total ionizing dose for three different process variants from the 90nm technology. More variability is observed for narrow width devices compared to wider devices before and after irradiation. Device-to-device variability is compared for two technologies (65 and 90nm) and three process variants (low, standard, and high threshold voltage). These results illustrate the importance of process-induced variability on the radiation response of MOS devices and integrated circuits. [Copyright &y& Elsevier]

Electronic structure calculations and irradiation measurements are used to obtain insight into oxide trapped charge mechanisms in varying hydrogen ambients. Quantitative agreement between measured and simulated oxide and interface-trap charge densities is obtained over a wide range of H2 concentrations by implementing first-principles calculations of the energetics, and dynamics of charge transport and trapping, into TCAD simulations of irradiated MOS structures. Hole trapping dominates for typical H2 densities, but protons can dominate at high H2 densities. The rate of the interface trap reaction, in which protons that are liberated from charged oxygen vacancies by molecular hydrogen form dangling bonds on the interface, is found to play a key role in determining the relative concentrations of oxide and interface-trap charge densities. [ABSTRACT FROM AUTHOR]

A physics-based TCAD model for enhanced low-dose-rate sensitivity in linear bipolar devices is developed. Quantitative agreement is found with measured data over a wide range of dose rates and H2 concentrations. Analysis of the degradation effects of individual defect types, the implementation of which has been informed by first principles calculations, provides insights into the mechanisms behind enhanced low-dose-rate effects in different hydrogen environments. The effects of initial defect concentration and location and the energetics of the defect-related reactions are explored. Conclusions are drawn about the roles of molecular hydrogen and hydrogenated defects in the radiation response of these devices. [ABSTRACT FROM PUBLISHER]

InAs–AlSb high-electron mobility transistors stressed with hot carriers may exhibit shifts in the peak transconductance toward more negative gate-voltages. The devices are most degradation prone in operating conditions with high longitudinal (in the direction of IDS) electric fields in the channel. Room-temperature annealing, gate current, and channel-mobility measurements suggest the presence of a metastable defect in the top AlSb layer. Device simulations and first-principles quantum–mechanical calculations are used to investigate the physical nature of the defects responsible for degradation. Metastable configurations of substitutional and interstitial oxygen have charge states and transition energies consistent with the degradation trends. [ABSTRACT FROM PUBLISHER]

Abstract: The sensitivity of radiation-induced source–drain leakage to the amount of recess in the shallow-trench isolation (STI) of CMOS technologies is reported. The impact of the doping profile along the STI sidewall on the magnitude of the leakage current is quantified. The sensitivity of the radiation-induced leakage current to these parameters provides insight into how process variability is manifested as variations in the radiation response. [Copyright &y& Elsevier]

The energetics of the interactions between molecular hydrogen and common defects in \SiO2 that are typically associated with O deficiency have been obtained using atomic-scale quantum mechanical calculations. \H2 does not easily crack at neutral vacancies, but it will crack efficiently at O vacancy sites that have captured a hole and relaxed into the puckered configuration of an \E\gamma^{\prime} defect, releasing a proton into the oxide. Isolated Si dangling bonds also can play a role in cracking \H2, depending on their concentration in the oxides. These results provide significant insight into the underlying causes of latent interface trap buildup in MOS devices and enhanced low-dose-rate sensitivity in linear bipolar devices. [ABSTRACT FROM AUTHOR]

The dependence of the subthreshold-swing (SS) degradation on fin width is reported for irradiated 100-nm-gatelength, fully depleted n-channel FinFETs. The wider the fin is, the greater the radiation-induced SS degradation. The higher tolerance to radiation-induced charge for the narrower FinFETs is attributed to the additional lateral gate control over the body potential. The irradiation and room temperature annealing results suggest that the SS increase for wider FinFETs is due primarily to nonuniform trapped charge in the buried oxide (BOX). The subthreshold characteristics of FinFETs with two fins are more likely to exhibit a nonuniform subthreshold slope (NUSS), resulting from fin-to-fin variability, than FinFETs with 20 fins, where the corresponding Id-Vgs curve is the composite of the 20 individual IdVgs curves. [ABSTRACT FROM AUTHOR]

We have investigated the effects of biased and unbiased X-ray irradiation on the subsequent time-dependent dielectric breakdown (TDDB) of 130-nm MOSFETs irradiated up to 1 Mrad(SiO2). We found a small but measurable increase in TDDB lifetime after irradiation at the worst-case irradiation bias. The influence of radiation bias on subsequent TDDB is more significant in the PMOSFETs than the NMOSFETs. The increased TDDB lifetime and the irradiation-bias dependence are attributed to the influence of radiation-induced traps on the stressing current during the reliability testing. [ABSTRACT FROM AUTHOR]

Low-frequency (1/f) noise measurements were performed at room temperature as a function of gate bias on field-oxide field effect transistors (FOXFETs) that were irradiated with 10-keV X-rays and then annealed at room temperature. The resulting oxide-trap and interface-trap charge densities were estimated by the midgap charge separation technique. Some devices also were exposed to 85% relative humidity at 130degC for three days after irradiation and annealing. Effective border trap densities were estimated from noise measurements in each case. The noise magnitude increases after irradiation and decreases first during annealing and then even more significantly after moisture exposure. The post-humidity-exposure noise for the irradiated devices is well below the pre-irradiation noise for these devices and experimental conditions. The increased noise due to irradiation is attributed to O vacancies and hydrogen bridge (Si-H-Si) defects in the near-interfacial field oxide. The reduction in noise with room-temperature annealing and humidity exposure is due to a combination of thermal and tunnel annealing processes and defect passivation reactions involving water. [ABSTRACT FROM PUBLISHER]

Swift heavy ion (SHI) damage, including single-event gate rupture (SEGR), radiation-induced soft breakdown (RISB), and long-term reliability degradation (LTRD), plays an important role in limiting device lifetime and reliability. However, the atomic-scale physical origins of these phenomena have not been elucidated. In this work, we explain the underlying physical processes responsible for SHI-induced effects in oxides, providing a direct link between atomic motion and macroscopic electrical effects. SRIM 2008 calculations show that SHIs produce low-energy atomic recoils in SiO2. Using parameter-free quantum mechanical calculations, we probe the atomic-scale dynamics of the resulting low-energy atomic displacements. We show that low-energy displacements in SiO2 produce pockets containing high densities of network defects, and that these defects generate electronic states throughout the SiO2 band gap. These spatially correlated defect states represent a low-resistivity ldquoconducting piperdquo through SiO2 layers, and provide an atomistic mechanism for the formation of electrically-active damage that does not rely on thermal spike effects. In the case of SEGR, the conducting pipe allows energy stored on the gate capacitance to be discharged into the oxide, resulting in the permanent damage observed experimentally. The persistence of defects resulting from SHI-induced atomic displacements provides a physical explanation for percolation models of LTRD and RISB. [ABSTRACT FROM PUBLISHER]

The effects of gate length and drain bias on the off-state drain leakage current of irradiated fully-depleted SOI n-channel MOSFETs are reported. The experimental results are interpreted using a model based on the combined effects of band-to-band tunneling (BBT) and the trapped charge in the buried oxide. For negative gate-source voltages, the drain leakage current increases with the drain voltage because the electric field in the gate-to-drain overlap region is increasing. The off-state current in these devices increases with total ionizing dose due to oxide trapped charge build up in the buried oxide, enhanced by the BBT mechanism. The experimental data show that these effects are more significant for devices with shorter gate-lengths. Simulation results suggest that the BBT-generated holes are more likely to drift all the way from the drain to the source in shorter devices, enhancing the drain leakage current, while they tend to tunnel across the gate oxide in longer devices. [ABSTRACT FROM PUBLISHER]