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Random telegraph noise (RTN) measurements are performed on as-processed, programmed, erased, and irradiated 80 nm vertical charge-trapping nand memory transistors. Variations in current with time of up to ±20% are observed during the RTN testing interval. The RTN of these devices is relatively unaffected by irradiation of devices to 500 krad(SiO2). Root-mean-square (rms) magnitudes of measured RTN exceed predictions of number-fluctuation models (NFMs) by up to six-times. This result demonstrates that fluctuations in carrier scattering rates caused by motion and/or reconfiguration of traps at grain boundaries likely lead to a significant fraction of the low-frequency noise and/or RTN in poly-crystalline Si channel, charge-trapping memory devices. The magnitudes of these fluctuations may present significant challenges to the resolution of highly scaled 3-D memory devices.

Commercial Schottky-gate AlGaN/GaN high-electron-mobility transistors (HEMTs) exhibit a large peak in low-frequency (LF) noise magnitude at $\sim $ 325 K. An activation energy of 0.56 ± 0.05 eV is determined for the responsible generation–recombination (G–R) center via Arrhenius analysis. Comparisons with first-principles calculations and complementary experimental studies show that this G–R center is due to substitutional iron impurities, FeGa. Independent determination of the activation energy for this prominent noise peak enables recalibration of the Dutta–Horn model of LF noise for GaN-based HEMTs and a downward revision by $\sim $ 20% of past LF-noise estimates of effective defect energies. The resulting LF-noise-derived defect-energy distributions are consistent with deep-level-transient spectroscopy (DLTS) measurements on GaN-based diodes before and after 1.8-MeV proton irradiation. The activation of FeGa-related centers via defect dehydrogenation during high-voltage stress is demonstrated via LF noise measurements on AlGaN/GaN-on-SiC HEMTs.

In this work, a thorough assessment of the robustness of complementary channel HfO2 ferroelectric FET (FeFET) against total ionizing dose (TID) radiation is conducted, with the goal of determining its suitability for use as high-performance and energy-efficient embedded nonvolatile memory (eNVM) for space applications. We demonstrate that: i) ferroelectric HfO2 thin film is robust against X-ray and proton irradiation; ii) FeFET exhibits a polarization state dependent radiation sensitivity where the high- ${V} {_{\text {TH}}}$ (HVT) state sees noticeable negative ${V} {_{\text {TH}}}$ shift and low- ${V} {_{\text {TH}}}$ (LVT) is immune to irradiation, irrespective of the channel type; iii) the state dependence is ascribed to the depolarization field in the HVT, which points toward the channel and facilitates the transport and trapping of radiation-generated holes close to the channel. In the future, radiation hardening techniques need to be considered.

The properties of defects in n-p-n Si bipolar junction transistors (BJTs) caused by 17-MeV Si ions are investigated via current–voltage, low-frequency (LF) noise, and deep level transient spectroscopy (DLTS) measurements. Four prominent radiation-induced defects in the base–collector junction of these transistors are identified via DLTS. At least two defect levels are observed in temperature-dependent LF 1/f noise measurements, one that is similar to a prominent defect in DLTS and another that is not. Defect microstructures are discussed. Our results show that DLTS and 1/f noise measurements can provide complementary information about defects in linear bipolar devices.

A probabilistic total ionizing dose (TID) failure assessment is extended to include survivor data, enabling the bounding of failure probability to a desired confidence level (CL) without failure data. The extension provides an avenue for analyzing microelectronics tested for TID without reaching a failure mode, a scenario often encountered by missions utilizing commercial-off-the-shelf (COTS) technologies. Using the type-I censored likelihood formulation and a realistic upper bound on expected device performance, the failure probability space is bounded by confidence contours within the context of a variable environment. The framework accommodates any type of distribution assumed for the part failure or the environment under consideration. Furthermore, the framework can be utilized pre-emptively to plan future device TID tests, minimizing costs while meeting survival requirements. Heritage data may also be used as survivors to further minimize testing costs when parts are from the same lot, but the amount of constraint derived from heritage is limited. Altogether, the framework enables a formal, mathematically rigorous analysis of radiation tolerant devices tested to a maximum dose, as well as flight heritage, in a hardness assurance methodology.

We provide comprehensive experimental data and technology computer-aided design (TCAD) simulations to clarify total-ionizing-dose mechanisms in 16-nm Si FinFETs. In n-channel FinFETs irradiated to ultrahigh doses, the transconductance evolution rebounds (increase up to 3–10 Mrad followed by a decrease), while the drain-to-source leakage current steadily augments until reaching a plateau at very large doses. These effects result from positive charge trapping deep in the sidewalls of the shallow trench isolation (STI) and negative trapped charge accumulation localized in the upper STI corners. Larger sizes of inter-fin STI enhance the leakage current degradation of transistors with smaller numbers of fins. Hydrogen-induced border- and/or interface-trap generation at the Si/oxide interface at the STI corners leads to increased low-frequency noise (LFN) at doses $>{10}$ Mrad(SiO2). These results show that the quality of oxides and interfaces in the upper region of the STI adjacent to the device channel is crucial for the tolerance to ultrahigh radiation of modern FinFET technologies.

A re-evaluation of experimental results within the context of first-principles calculations strongly suggests that interface traps can contribute significantly to low-frequency (1/ $f$ ) noise in irradiated MOS devices. Hydrogen-induced trap activation and passivation are likely origins of the observed fluctuations. Measured and calculated activation energies for hydrogen drift, diffusion, and dissociation are consistent with energetics of 1/ $f$ noise. The dominant noise source is determined by densities of relevant defect precursors, hydrogen concentrations, device processing, and history. When present, hydrogen-induced interface-trap activation and passivation adds to noise due to border traps. These results should help assess and assure the performance and reliability of analog integrated circuits in high radiation environments.

Total-ionizing-dose (TID) effects are evaluated in top-gated IGZO thin-film transistors (TFTs) irradiated with different gate biases. Negative-bias irradiation leads to worst case degradation of TID response, primarily due to enhanced charge trapping in the SiO2 insulator that underlies the IGZO channel and serves as an oxygen-penetration layer during device processing. TID response comparisons with back-gated devices indicate that hydrogen also plays an important role in the observed degradation of top-gated devices. The source of this hydrogen is most likely SiN oxygen blocking layers. Comparisons with other display and alternative-channel MOS technologies illustrate that further optimization should enable the use of IGZO in future space applications.

Damage separation analysis was performed for two types of bipolar junction transistors (BJTs) following proton irradiation over the energy range of 1.6–650 MeV. The functional dependence of excess base current on fluence for each device type is consistent with base polarity as it relates to the effect of oxide-trapped charge on surface recombination. For a given fluence, the excess base current decreases with proton energy due to reductions in non-ionizing energy loss (NIEL) and stopping power. Relative damage coefficients, computed from normalized $\Delta I_{\mathrm {B}}$ versus fluence curves, imply a mix of ionization and displacement damage. The relative amounts of ionization damage and displacement damage as a function of proton energy are consistent with charge yield (CY), stopping power and NIEL. A simple model for the energy dependence of damage contributions, based on CY and the relative amounts of deposited ionizing and non-ionizing energy, is described. The model calculations as a function of proton energy are in good agreement with the relative damage contributions estimated from the damage separation analysis.

Total-ionizing-dose (TID) effects are evaluated in back-gated indium–gallium–zinc oxide (IGZO) thin-film transistors irradiated under different gate biases. Negative-bias irradiation leads to worst-case degradation of TID response in these devices, primarily as a result of enhanced charge trapping in the SiO2 overlayer. The relatively small peak transconductance decrease after irradiation illustrates that IGZO transistors are much less sensitive to interface-trap buildup and other instabilities due to hydrogen release and transport than amorphous Si thin film transistors examined previously. The TID response of devices with different gate sizes is also investigated. No significant geometry dependence is observed, which is promising for future scaling down of the technology.

Total-ionizing-dose (TID) effects in AlGaN/GaN high-electron-mobility transistors (HEMTs) are evaluated by dc and low-frequency noise measurements. Devices with and without passivation layers are irradiated with 10-keV X-rays up to 100 Mrad(SiO2) under different bias conditions. Irradiated devices show significant electrical shifts in threshold voltage and transconductance. At doses < 10 Mrad(SiO2), the TID-induced effects are related to the passivation of preexisting acceptor-like defects via hole capture, which induces negative threshold voltage shifts and improvement of transconductance. At doses $>$ 10 Mrad(SiO2), dehydrogenation of defects and impurity complexes leads to the creation of acceptor-like defects, which degrade the transconductance, shift positively the threshold voltage, and increase the low-frequency noise. Effects are enhanced in unpassivated devices and when the gate is biased at high voltage.

Total-ionizing-dose (TID) responses are investigated for fully depleted silicon-on-insulator (FDSOI) ring oscillators (ROs) in 3-D architectures. Operational frequencies decrease after irradiation in these devices due primarily to threshold voltage shifts and transconductance degradation due to interface-trap buildup in the pull-up $p$ MOSFETs. 3-D sequentially integrated FDSOI ROs fabricated in the bottom layer of the 3-D structure show the most significant frequency degradation. The ac-bias irradiation leads to greater shifts than static-bias irradiation in these devices due to enhanced interface-trap buildup. Circuit simulations reinforce the relative importance of transconductance degradation in pull-up $p$ MOSFETs to the TID response of these ROs.

Total ionizing dose (TID) irradiation and low-frequency noise characterization are performed on carbon nanotube field-effect transistors (CNTFETs). Large hysteresis due to high border-trap densities is observed in as-processed and irradiated devices. TID irradiation also leads to significant radiation-induced charge trapping in the surrounding dielectrics resulting in parametric degradation. Percolation-path switching and border traps contribute to low-frequency noise, with a relatively more prominent role for border traps after irradiation than before irradiation. These results show that process improvements are required to optimize both the initial operating characteristics and the radiation response of CNTFETs.

Negative bias-temperature instabilities and low-frequency noise are investigated in strained Ge ${p}$ MOS FinFETs with SiO textsubscript 2/HfO textsubscript 2 gate dielectrics. The extracted activation energies for NBTI in Ge ${p}$ MOS FinFETs are smaller than for Si ${p}$ MOSFETs. Low-frequency noise magnitudes at lower temperatures are unaffected by negative-bias-temperature stress (NBTS), but increase significantly for temperatures above $\sim 230$ K. The increased noise due to NBTS is attributed primarily to the activation of oxygen vacancies and hydrogen-related defects in the SiO2 and HfO2 layers.

Effects of programming/erasing (P/E) and total-ionizing dose (TID) are investigated on 2- and 40-fin charge-trap transistors (CTTs) fabricated in a 14-nm bulk-Si CMOS technology. Significant random telegraph noise (RTN) is observed in as-processed CTTs, especially for 2-fin devices. Trapped charge in programed devices does not significantly affect 1/ ${f}$ noise magnitudes, but P/E leads to trap activation/deactivation, causing changes in border-trap energy and spatial distributions. TID irradiation activates a large number of stable radiation-induced traps.

The effects of geometry and cycling are evaluated for charge-trapping NAND memory devices with SiON tunneling layers. Processing splits include SiON tunneling layers with and without $\text{H}_{2}/\text{D}_{2}$ high-pressure annealing. Programed and erased devices were irradiated up to 500 krad(SiO2) with 10-keV X-rays. Excellent retention and endurance are demonstrated for these devices before and after irradiation. Scaling devices to smaller dimensions enhances program/erase efficiency and radiation tolerance.

The temperature dependence of low-frequency noise is investigated from 80 to 320 K for nMOS and pMOS bulk Si FinFETs with SiO2/HfO2 gate dielectrics. Both types of devices show excellent stability during bias-temperature stress and high total-ionizing dose (TID) irradiation. nMOSFET 1/ $f$ noise generally decreases as measuring temperature increases, with three prominent individual defect-related peaks. These peaks in noise magnitude are most likely due to hydrogen shuttling near the interface and/or O vacancies in the HfO2. In contrast, the 1/ $f$ noise in pMOSFETs generally increases with increasing temperature without prominent peaks in noise magnitude. The gate-voltage dependence of low-frequency noise also is evaluated at different temperatures for both device types. Results confirm that the nMOS devices have effective border-trap energy distributions that are nonuniform and generally increase toward midgap, and the pMOS devices have more uniform defect-energy distributions that increase monotonically toward the valence band.

We investigate the influence of high energy photons and thiol ligands on the photophysical properties of sub-monolayer CdTe/CdS quantum dots (QDs) immobilized in porous silica (PSiO2) scaffolds. The highly disperse, uniform distributions of QDs in a three-dimensional PSiO2framework ensure uniform interaction of not only radiation but also subsequent surface repassivation solutions to all immobilized QDs. The high optical densities of QDs achieved using PSiO2enable straightforward monitoring of the QD photoluminescence intensities and carrier lifetimes. Irradiation of QDs in PSiO2by high energy photons, X-rays, and γ-rays leads to dose-dependent QD photodarkening, which is accompanied by accelerated photooxidative effects in ambient environments that give rise to blue-shifts in the peak QD emission wavelength. Irradiation in an oxygen-free environment also leads to QD photodarkening but with no accompanying blue-shift of the QD emission. Significant reversal of QD photodarkening is demonstrated following QD surface repassivation with a solution containing free-thiols, suggesting reformation of a CdS shell, etching of surface oxidized species, and possible reduction of photoionized dark QDs to a neutral, bright state. Permanent lattice displacement damage effects may contribute toward some irreversible γ radiation damage. This work contributes to an improved understanding of the influence of surface ligands on the optical properties of QDs and opens up the possibilities of engineering large area, low-cost, reuseable, and flexible QD-based optical radiation sensors.

The development of engineering-level models requires adoption of physical mechanisms that underlie observed phenomena. This paper reviews several cases where parameter-free, atomic-scale, quantum mechanical calculations led to the identification of specific physical mechanisms for phenomena relating to performance, reliability, radiation effects, and aging issues in microelectronics. More specifically, we review recent calculations of electron mobilities that are based on atomic-scale models of the Si-SiO2 interface and elucidate the origin of strain-induced mobility enhancement. We then review extensive work that highlights the role of hydrogen as the primary agent of reliability phenomena such as Negative Bias Temperature Instability (NBTI) and radiation effects, such as Enhanced Low Dose Radiation Sensitivity (ELDRS) and dopant deactivation. Finally, we review atomic-scale simulations of recoils induced by energetic ions in Si and SiO2. The latter provide a natural explanation for single-event gate rupture (SEGR) in terms of defects with energy levels in the SiO2 band gap.

We have exposed MOS gate and field oxide transistors to moisture treatments with all pins grounded for up to three weeks. Irradiated field oxide structures showed a significant decrease in low frequency noise with moisture treatment, due to the passivation of Si dangling bonds at or near the Si/SiO2 interface. With moisture exposure, pMOS gate oxide transistors showed significant increases in pre-irradiation 1/f noise and post-irradiation oxide- and interface-trap charge densities. The 1/f noise of nMOS gate oxide transistors shows much less sensitivity to moisture exposure than pMOS transistors, before and after irradiation. We attribute these differences in sensitivities to moisture treatment to the enhancement of water diffusion in SiO2 by B atoms in the oxides that overlie the source/drain junctions of the pMOS transistors, in contrast to the retardation of moisture diffusion by P atoms in the corresponding regions of the nMOS devices.

Temperature and electrical stress induced degradation in the characteristics is reported for germanium substrate MOS capacitors with HfO2/HfSiON gate dielectrics. The accumulation capacitance decreases with temperature stress due to diffusion of germanium into the high-k dielectric. The interface trap and border trap densities decrease due to temperature stress-induced oxide growth at the oxide-germanium interface.

Bias-temperature-instabilities (BTIs) are investigated for 4H-SiC based nMOSFETs before and after total ionizing dose irradiation. We find that the threshold voltage shifts of unirradiated devices decrease significantly with elevated-temperature stress under accumulation bias; in contrast, devices stressed under inversion bias do not exhibit significant threshold voltage shifts. Threshold voltage shifts due to BTI for unirradiated devices stressed under accumulation bias may well be enhanced significantly as a result of the additional ionization of deep dopants in SiC at elevated temperatures. The BTIs are caused by charge carriers are captured by deep interface traps (more than 0.6 eV away from the SiC conduction or valence bands) and O vacancies in the SiO2. Hole trapping at O vacancies dominates the ionizing radiation response. The magnitudes of the changes in threshold voltage shifts increase with switched bias-temperature stress after irradiation, relative to those in unirradiated devices.

Temperature and electrical stress induced degradation in the characteristics is reported for germanium substrate MOS capacitors with HfO2/HfSiON gate dielectrics. The accumulation capacitance decreases with temperature stress due to diffusion of germanium into the high-κ dielectric. The interface trap and border trap densities decrease due to temperature stress-induced oxide growth at the oxide-germanium interface.

We have exposed MOS gate and field oxide transistors to moisture treatments with all pins grounded for up to three weeks. Irradiated field oxide structures showed a significant decrease in low frequency noise with moisture treatment, due to the passivation of Si dangling bonds at or near the Si/SiO2 interface. With moisture exposure, pMOS gate oxide transistors showed significant increases in pre-irradiation 1/f noise and post-irradiation oxide- and interface-trap charge densities. The 1/f noise of nMOS gate oxide transistors shows much less sensitivity to moisture exposure than pMOS transistors, before and after irradiation. We attribute these differences in sensitivities to moisture treatment to the enhancement of water diffusion in SiO2 by B atoms in the oxides that overlie the source/drain junctions of the pMOS transistors, in contrast to the retardation of moisture diffusion by P atoms in the corresponding regions of the nMOS devices.

The development of engineering-level models requires adoption of physical mechanisms that underlie observed phenomena. This paper reviews several cases where parameter-free, atomic-scale, quantum mechanical calculations led to the identification of specific physical mechanisms for phenomena relating to performance, reliability, radiation effects, and aging issues in microelectronics. More specifically, we review recent calculations of electron mobilities that are based on atomic-scale models of the Si-SiO2 interface and elucidate the origin of strain-induced mobility enhancement. We then review extensive work that highlights the role of hydrogen as the primary agent of reliability phenomena such as Negative Bias Temperature Instability (NBTI) and radiation effects, such as Enhanced Low Dose Radiation Sensitivity (ELDRS) and dopant deactivation. Finally, we review atomic-scale simulations of recoils induced by energetic ions in Si and SiO2. The latter provide a natural explanation for single-event gate rupture (SEGR) in terms of defects with energy levels in the SiO2 band gap.

Approximately 90 papers were presented in oral or poster format at the 1990 NSRE Conference held July 16-20 in Reno, Nevada. More than 90 percent of the papers submitted for review were turned in by Wednesday of the conference. This enabled the editors to distribute nearly all of the papers to reviewers at the conference site, thereby lightening the editors' luggage and getting the review process off to a fast start.