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Deposition of metallic impurities from HF process solutions has been investigated experimentally and explained theoretically in a qualitative manner. The depositions are shown to be electrochemical in nature in that an oxidation reduction reaction results in metal ions in solution depositing on the wafer as elements with an oxidation state of 0. The theory is only qualitative in that it can only predict which metals will deposit, not how much. Experimentally, simple transmission equations can be determined which relate metallic contamination levels on Si wafer surfaces (atoms/[cm.sup.2]) to metal concentration in the solution (ppb). Simple test structures have been fabricated with known amounts of iron and copper contamination in the pregate oxide clean of a 1.25 [[micro]meter] CMOS process. Device measurements indicate device degradation in the case of copper, confirming deposition studies that copper deposits from HF solutions. Iron contaminated wafers show no contamination related device effects, in support of theoretical predictions and deposition studies indicating iron does not deposit from HF solutions. The importance and potential usefulness of test structures as homogeneous contamination monitors is illustrated through device modeling of the contamination effects observed in the test structures that can then be used to estimate the effects of such contamination on ULSI circuit performance.

A study to simulate the single-event burnout of n-channel power metal oxide semiconductor field effect transistor is presented. It investigates the failure mechanism caused by the transport of a heavy ion within the device during operation in a space environment. A model, that takes into account a parasitic bipolar junction transistor and its feedback scheme, is also presented for predicting the susceptibility of such a MOSFET to burn-out.

The temperature dependence of single-event burn out (SEB) in n-channel power metal-oxide-semiconductor field effect transistors (MOSFETs) is investigated experimentally and analytically. Experimental data are presented which indicate that the SEB susceptibility of the power MOSFET decreases with increasing temperature. A previously reported analytical model that describes the SEB mechanism is updated to include temperature variations. This model is shown to agree with the experimental trends.

Analog-to-digital converters (ADCs) with different topologies respond differently to total ionizing dose (TID). A flexible behavioral modeling approach is proposed for system-level simulation of TID effects in successive-approximation-register (SAR) ADCs. The radiation-enabled approach can be adapted for a wide range of ADCs of various resolutions, clock speeds, and manufacturers. The empirical model is calibrated and validated, pre-rad and post-rad, for a particular ADC. Pre-rad calibration is performed by introducing distributions of static parameters corresponding to datasheet specifications. The post-rad calibration is accomplished by introducing error sources associated with the comparator and digital-to-analog converter (DAC), corresponding to experimental data. The calibrated model is used to examine the dynamic performance and to estimate the probability of parametric failure during the mission lifetime. [ABSTRACT FROM AUTHOR]

Modeling systems containing commercial-off-the-shelf (COTS) parts exposed to total ionizing dose (TID) are difficult due to large parameter variability in the parts as a function of dose. This article provides a rapid approach to predicting the system performance as a function of TID given these parameter variations. A radiation-aware model for an IRF510 power MOSFET is generated from a small population of irradiated parts, and this model is randomly sampled for each of the transistors in an example circuit, utilizing the degraded parameters. The simulations predict the circuit operating in one of three distinct modes, with circuits containing large variability in parts failing in some instances. The simulated data are compared to experimental data using a method that involves interchanging irradiated parts in a socketed printed circuit board (PCB) to produce a large number of different combinations of test circuits. The simulated data correctly predicted the circuit modes of operation, and the part-swapping technique eliminated the cost of building many test boards. [ABSTRACT FROM AUTHOR]

Peak transient currents due to pulsed-laser or heavy-ion irradiation of Ge $p$ MOS FinFETs are nearly independent of gate bias. This is because the prompt photocurrent is due primarily to a transient source–drain shunt. In contrast, long-term diffusion charge collection is strongly gate-bias dependent. This bias dependence results from hole injection from the source in response to the transient increase in electron concentration in the channel. The transients measured at the source terminal change polarity when the strike location moves from the source to the drain, but this effect does not occur for the transients measured at the drain terminal. Charge collection mechanisms are studied using TCAD simulations. [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]

Gate-all-around (GAA) silicon nanowire (NW) CMOS transistors demonstrate outstanding total-ionizing-dose (TID) tolerance due to the ultrascaled gate dielectric thickness, enhanced electrostatic gate control, and suppression of parasitic leakage current paths. nFETs and pFETs show similar TID responses, making the GAA NW technology an excellent candidate for CMOS IC applications in high-radiation environments. The slight degradation of the threshold voltage suggests limited charge buildup in the gate dielectrics. However, low-frequency noise and random telegraph noise measurements show the importance of change in trap configurations in both the near-interfacial SiO2 and HfO2 dielectric layers to the radiation response and reliability of GAA NW devices. These traps are most likely due to oxygen vacancies and/or hydrogen complexes. [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]

Heavy-ion, focused X-ray, and pulsed laser single-event transient (SET) experiments are performed on a silicon epitaxial diode. Collected charge, transient rise times, and transient fall times are calculated and compared between different sources. The transient shape characteristics depend on the source (ion, X-ray, or laser), even when similar amounts of charge are generated. The observed differences are examined and explained in terms of basic charge collection mechanisms. [ABSTRACT FROM AUTHOR]

The energy distributions of electrons in gate-all-around (GAA) Si MOSFETs are analyzed using full-band 3-D Monte Carlo (MC) simulations. Excellent agreement is obtained with experimental current–voltage characteristics. For these 24-nm gate length devices, the electron distribution features a smeared energy peak with an extended tail. This extension of the tail results primarily from the Coulomb scattering within the channel. A fraction of electrons that enter the drain retains their energy, resulting in an out-of-equilibrium distribution in the drain region. The simulated density and average energy of the hot electrons correlate well with experimentally observed device degradation. We propose that the interaction of high-energy electrons with hydrogen-passivated phosphorus dopant complexes within the drain may provide an additional pathway for interface-trap formation in these devices. [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]

Heavy-ion measurements are used to define a multiply nested sensitive-volume model for a 180-nm static random access memory (SRAM) test structure using the Monte Carlo radiative energy deposition (MRED) tool. We demonstrate that the fundamental assumptions of simple rectangular-parallelepiped (RPP) or integral-RPP models are inappropriate for single-event latchup (SEL) in this test structure, indicating that more advanced modeling is needed. We develop an MRED model that agrees well with latchup data at normal incidence and at roll and tilt angles of 60°. This process should facilitate estimates of SEL cross section and event rates for this and similar technologies in space environments. [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]

Four D flip-flop (DFF) layouts were created from the same schematic in Sandia National Laboratories’ CMOS7 silicon-on-insulator (SOI) process. Single-event upset (SEU) modeling and testing showed an improved response with the use of shallow (not fully bottomed) N-type metal-oxide-semiconductor field-effect transistors (NMOSFETs), extending the size of the drain implant and increasing the critical charge of the transmission gates in the circuit design and layout. This research also shows the importance of correctly modeling nodal capacitance, which is a major factor determining SEU critical charge. Accurate SEU models enable the understanding of the SEU vulnerabilities and how to make the design more robust. [ABSTRACT FROM AUTHOR]

Effects of additional thermal budget associated with a three-dimensional (3D) fabrication sequence are evaluated for the total-ionizing dose radiation response of fully depleted silicon-on-insulator (FD-SOI) MOSFETs. Current-voltage and low-frequency (1/ ${f}$) noise measurements are compared for (1) conventional planar FD-SOI MOSFETs, and (2) MOSFETs formed in the bottom layer of the 3D process and subjected to the process steps associated with formation of a second active layer. Similar radiation-induced voltage shifts and increases of 1/ ${f}$ noise are observed after irradiation for both types of structures. These similar changes in response show that the additional thermal processing involved with 3D fabrication has little effect on border-trap densities and radiation-induced charge trapping in gate and/or buried oxides of MOSFETs formed in the bottom layer of the 3D process. [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]

Variability of the solar energetic particle environment is investigated for single-event burnout (SEB) reliability of silicon carbide power metal-oxide-semiconductor field-effect transistors. A probabilistic assessment of failure evaluates the benefits of derating voltage, shielding, and mission length. The Prediction of Solar particle Yields for Characterizing Integrating Circuits code is used to calculate a cumulative density function for the fluence of the environment. The lethal ion method is then used to determine what proportion of the environment will cause SEB. The operating voltage determines the lowest linear energy transfer (LET) particle that will cause SEB, and that should be included in the environment distribution. The shielding and mission length also determines the final environment distribution of the mission fluence. When the critical LET for a device is relatively low for the expected mission environment, the method in this article can calculate the probability of failure from a destructive event. The calculated probability of failure enables the consideration of part use outside the safe operating area, especially when derating the operating voltage would eliminate the technology advantage of the part. [ABSTRACT FROM AUTHOR]

Neuromorphic computing endeavors to imitate the way biological brains process information and solve problems. Uses for neuromorphic computing span disciplines and include applications in image processing, audio processing, optimization, and more. This work explores the effect of proton-induced single-event upsets (SEUs) on a neuromorphic computing architecture engaged in image recognition. Two main results are found. One, the overall classification accuracy is unchanged although a high number of hidden, tolerable errors occurred. Additionally, SEUs are found to alter the relative occurrence of false positives and false negatives, which occurred despite the overall classification accuracy remaining unaffected. [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]

Total-ionizing-dose mechanisms are investigated in 16-nm InGaAs FinFETs with an HfO2/Al2O3 gate-stack. Transistors are irradiated up to 500 krad(SiO2) and annealed at high temperatures. Irradiated devices show negative threshold-voltage Vth shifts, subthreshold stretch-out, and leakage current increases. These result from positive charge trapping in the gate oxide and shallow trench insulators, and increases in the interface and border-trap charge densities. Low-frequency noise measurements at different temperatures indicate a significant increase of noise magnitude in irradiated devices at an activation energy of ~0.4 eV. Density functional theory (DFT) calculations strongly suggest that transistor Vth shifts are due primarily to hole trapping at oxygen vacancies in HfO2, and the increased noise is due primarily to O vacancies in Al2O3. Additional contributions to the noise from defects in the GaAs buffer layer are also likely, primarily at low temperatures. [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]

A sensitive volume is developed using pulsed laser-induced collected charge for two bias conditions in an epitaxial silicon diode. These sensitive volumes show good agreement with the experimental two-photon absorption laser-induced collected charge at a variety of focal positions and pulse energies. When compared to ion-induced collected charge, the laser-based sensitive volume overpredicts the experimental collected charge at low bias and agrees at high bias. A sensitive volume based on ion-induced collected charge adequately describes the ion experimental results at both biases. Differences in the amount of potential modulation explain the differences between the ion- and laser-based sensitive volumes at the lower bias. Truncation of potential modulation by the highly doped substrate, at the higher bias, results in similar sensitive volumes. [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]

A two-photon absorption technique is used to understand the mechanisms of single-event effects (SEEs) in silicon carbide power metal–oxide–field-effect transistors (MOSFETs) and power junction barrier Schottky diodes. The MOSFETs and diodes have similar structures enabling the identification of effects associated specifically with the parasitic bipolar structure that is present in the MOSFETs, but not the diodes. The collected charge in the diodes varies only with laser depth, whereas it varies with depth and lateral position in the MOSFETs. Optical simulations demonstrate that the variations in collected charge observed are from the semiconductor device structure and not from metal/passivation-induced reflection. The difference in the spatial dependence of collected charge between the MOSFET and diode is explained by bipolar amplification of the charge carriers in the MOSFETs. Technology computer-aided design (TCAD) device simulations extend this analysis to heavy-ion-induced charge collection. In addition, there is discussion comparing this analysis with experimental results from prior works that show enhanced charge collection resulting from heavy-ion irradiation. [ABSTRACT FROM AUTHOR]

This paper introduces a Monte Carlo (MC) approach based on the binary collision approximation to estimate defect types and densities in proton- and heavy-ion-irradiated graphene layers. The types and concentrations of defects that appear in graphene due to irradiation with various ions with energies ranging from ~100 keV to ~100 MeV are identified. This simple method enables defect introduction rates in graphene to be predicted to within better than a factor of two accuracy, relative to experimental measurements in a beam environment. The results demonstrate that all defects generated by ions with high incident energy are formed via head-on collisions and in-plane recoils, which is unique for 2-D materials. [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]

We report on the measurement and analysis of energetic heavy ion radiation effects on the mechanical properties of silicon carbide (SiC) crystals, by exploiting a vertical stack of micromachined vibrating SiC thin diaphragms integrated in a three-dimensional (3D) fashion. The diaphragms are 1 mm × 1 mm in lateral dimensions and 2 μm in thickness, vibrating at their multiple flexural modes in the range of 200 to 800 kHz. Upon 10.25 MeV oxygen ion irradiation, the 4 devices in the 3D stack exhibit saliently different changes in their multimode resonance frequencies. The device that is intended to capture most ions shows the largest frequency downshifts (∼6.6%–11.3%), corresponding to the extracted tension release from 382 MPa to 306 MPa, which can be explained by the maximum displacement damage in this device. The design of 3D integration not only scientifically enables probing different radiation effects in multiple devices simultaneously with clear controls but also economically evades very expensive, repetitive tests on individual devices, thus proving to be a powerful platform for analyzing and understanding radiation damage in micro/nanoelectromechanical systems and other micro/nanosystems. [ABSTRACT FROM AUTHOR]

Silicon-on-insulator latch designs and layouts that are robust to multiple-node charge collection are introduced. A general Monte Carlo radiative energy deposition (MRED) approach is used to identify potential single-event susceptibilities associated with different layouts prior to fabrication. MRED is also applied to bound single-event testing responses of standard and dual interlocked cell latch designs. Heavy ion single-event testing results validate new latch designs and demonstrate bounds for standard latch layouts. [ABSTRACT FROM AUTHOR]

The pulsed-laser single-event transient response of InGaAs FinFETs on bulk silicon substrates is investigated. Charge collection due to a source–drain shunt effect and drain-to-substrate junction charge collection contribute to the observed transients. The transient response of these silicon substrate devices is compared to that of InGaAs FinFETs on semi-insulating substrates. Faster transients with reduced peak currents and peak widths are observed on the silicon substrate devices. Simulations show hole collection by the silicon substrate. This reduces the amount of source-barrier lowering and bipolar-amplification relative to other III–V devices. Moreover, the reduced hole lifetime in the GaAs buffer layer also contributes to the relative reduction of the bipolar amplification in these devices. [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]

The thermalization process of sub-10-eV charge carriers is examined with treating carrier transport with full-band Monte Carlo simulations. The average energy loss (3.69 eV in Si and 2.62 eV in Ge) required to create a thermalized electron–hole pair, obtained from the simulations, is very close to the experimentally measured radiation–ionization energies of Si and Ge irradiated with high-energy particles. These results suggest that only interactions that occur after the radiation-generated charge carriers decay to energies of ~10 eV or less determine the fundamental property of the radiation–ionization energies. In addition to an energy loss equal to the band gap energy via impact ionization, acoustic-phonon emission, which has been omitted in prior work, contributes 30% of the remaining carrier energy loss, while optical-phonon emission contributes the other 70%. [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]

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.

Gate and drain bias dependences of hot carrier degradation are evaluated for AlGaN/GaN HEMTs fabricated via two different process methods. Both positive and negative threshold voltage $V_{\mathbf{th}}$ shifts are observed for each device type, depending on the mode and duration of the stress, indicating the presence of significant densities of donor-like and acceptor-like traps. Worst-case stress bias for transconductance degradation is the “ON” state for both device types. We find that transconductance degradation provides a more effective parameter to monitor defect buildup than $V_{\mathbf{th}}$ shifts, and that a single worst-case stressing bias condition cannot be defined for all varieties of AlGaN/GaN HEMTs. Low-frequency noise measurements versus temperature assist the identification of defects responsible for the observed degradation. Defect dehydrogenation and oxygen impurity centers are found to be particularly significant to the response of these devices. [ABSTRACT FROM AUTHOR]

Total-ionizing-dose effects on electrothermal micro- scanners are investigated using 10-keV X-rays and 14.3-MeV oxygen ions. The corresponding changes in mechanical displacement are measured using an optical microscope. Applied dc voltage and/or radiation-induced charging lead to changes in the vertical position and resistance of the structures. Radiation-induced changes in the vertical position and resistance and postirradiation recovery or superrecovery of these quantities are sensitive to dc biases applied during and/or after irradiation. Simple electrostatic and computational models are qualitatively consistent with observed trends in device response. [ABSTRACT FROM AUTHOR]

Heavy ion-induced single-event burnout (SEB) is investigated in high-voltage silicon carbide power MOSFETs. Experimental data for 1200-V SiC power MOSFETs show a significant decrease in SEB onset voltage for particle linear energy transfers greater than 10 MeV/cm2/mg, above which the SEB threshold voltage is nearly constant at half of the rated maximum operating voltage for these devices. TCAD simulations show a parasitic bipolar junction transistor turn-on mechanism, which drives the avalanching of carriers and leads to runaway drain current, resulting in SEB. [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]

The operation of transistorized Marx-bank circuits (MBCs) is analyzed, and physics-based modeling is used to understand the anomalous switching behavior of the first stage single trigger avalanche transistors of MBCs at high-current-injection conditions. The role of a voltage trigger pulse having variable rise time when applied to the base terminal is investigated to model the underlying physics of the anomalous switching behavior. Experimental observations related to ultrafast anomalous switching mechanisms of trigger transistor, i.e., either primary breakdown or current mode secondary breakdown, for faster and slower base drives are presented. This demonstrates the importance of the dynamic avalanche process and reverse saturation current on the switching mechanism under high-speed base-trigger ramps for different avalanche BJTs from various manufacturers and different lots. The agreement between 2-D TCAD device simulation results and the experimental observations shows the validity of the proposed theory when the base width and mobile carrier recombination rate are used as parameters in the device simulation setup. [ABSTRACT FROM AUTHOR]

Two-photon absorption (TPA) pulsed-laser testing is used to analyze the TPA-induced single-event latchup sensitive-area of a specially designed test structure. This method takes into account the existence of an onset region in which the probability of triggering latchup transits between 0 and 1 as the laser pulse energy increases. This variability is attributed to a combination of laser pulse-to-pulse variability and variations in local carrier density and temperature. For each spatial position, the latchup probability associated with a given energy is calculated. Calculation of latchup cross section at lower laser energies, relative to onset, is improved significantly by taking into account the full probability distribution. The transition from low probability of latchup to high probability is more abrupt near the source contacts than for surrounding areas. [ABSTRACT FROM PUBLISHER]