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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]

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]

Integrated silicon microwave pin diodes are exposed to 10-keV X-rays up to a dose of 2 Mrad(SiO2) and 14-MeV fast neutrons up to a fluence of $2.2\,\,\boldsymbol {\times }\,\,10\,\,^{\mathrm{ 13}}$ cm−2. Changes in both dc leakage current and small-signal circuit components are examined. Degradation in performance due to total-ionizing dose (TID) is shown to be suppressed by non-quasi-static (NQS) effects during radio frequency (RF) operation. Tolerance to displacement damage from fast neutrons is also observed, which is explained using technology computer-aided design (TCAD) simulations. Overall, the characterized pin diodes are tolerant to cumulative radiation at levels consistent with space applications such as geosynchronous weather satellites. [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 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]

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]

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]

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]

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]

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]

Silicon waveguide (WG) integrated p-i-n germanium photodiodes (PDs) from a monolithic electronic–photonic integrated circuit technology were exposed to ionizing radiation from a 10-keV X-ray source to investigate total ionizing dose effects. Existing work on radiation effects in PDs, which is almost entirely based on normal-incidence PDs (rather than WG-integrated PDs), is reviewed to provide context and a framework for understanding the measurement results. Back-end-of-line considerations suggest the enhancement of the ionizing dose due to high- $Z$ materials near the PD. PD performance was characterized in terms of dark current, S-parameters, dc photocurrent response, and optical-to-electrical conversion frequency response, shortly before and after irradiation. No significant degradation was observed, indicating that these devices may be suitable for applications in harsh radiation environments. [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]

Angular single-event (SE) mechanisms and experimental upset data for 14-/16-nm bulk fin field-effect transistor (FinFET) technologies are presented and analyzed. The discrete structure of FinFETs introduces unique geometrical and orientation dependences for angular SE mechanisms and SE upset (SEU) responses of FinFET circuits. Geometric analyses and 3-D technology computer-aided design results effectively explain the angular mechanisms behind experimentally observed SE crosssectional responses. Results show that angular SEU crosssectional characteristics can be attributed to the proportional contributions of charge deposition regions in the fin structure and the subfin bulk substrate. [ABSTRACT FROM PUBLISHER]

We have evaluated the total-ionizing-dose response of graphene-based X-ray detectors fabricated from graphene oxide (GO) via laser scribing. Raman characterization shows that the resulting structures exhibit the desired conversion of GO to graphene; both high- and low-resistance detectors are formed. The detectors are quite radiation sensitive, as demonstrated by fast pulse testing. The response time of the detectors degrades with total-ionizing dose exposure as a result of electron trapping at residual oxygen from unreacted GO and/or adsorbed oxygen on the graphene surface. [ABSTRACT FROM PUBLISHER]

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

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

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

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

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

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

We have measured the low-frequency 1/ f noise of Si0.55Ge0.45 p MOSFETs with a Si capping layer and SiO2/HfO2/TiN gate stack as a function of frequency, gate voltage, and temperature (100–440 K). The magnitude of the excess drain voltage noise power spectral density ( \textitS {vd} ) is unaffected by negative-bias-temperature stress (NBTS) for temperatures below ~250 K, but increases significantly at higher temperatures. The noise is described well by the Dutta-Horn model before and after NBTS. The noise at higher measuring temperatures is attributed primarily to oxygen-vacancy and hydrogen-related defects in the SiO2 and HfO2 layers. At lower measuring temperatures, the noise also appears to be affected strongly by hydrogen-dopant interactions in the SiGe layer of the device. [ABSTRACT FROM PUBLISHER]

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

We investigate negative-bias temperature instabilities in SiGe pMOSFETs with SiO 2/HfO 2 gate dielectrics. The measured activation energies for interface-trap charge buildup during negative-bias temperature stress are lower for SiGe channel pMOSFETs with SiO 2/HfO 2 gate dielectrics and Si capping layers than for conventional Si channel pMOSFETs with SiO 2 gate dielectrics. Electron energy loss spectroscopy and scanning transmission electron microscopy images demonstrate that Ge atoms can diffuse from the SiGe layer into the Si capping layer, which is adjacent to the SiO 2/HfO 2 gate dielectric. Density functional calculations show that these Ge atoms reduce the strength of nearby Si–H bonds and that Ge–H bond energies are still lower, thereby reducing the activation energy for interface-trap generation for the SiGe devices. Activation energies for oxide-trap charge buildup during negative-bias temperature stress are similarly small for SiGe pMOSFETs with SiO 2/HfO 2 gate dielectrics and Si pMOSFETs with SiO 2 gate dielectrics, suggesting that, in both cases, the oxide-trap charge buildup likely is rate-limited by hole tunneling into the near-interfacial SiO 2. [ABSTRACT FROM PUBLISHER]

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

Bias-temperature instabilities (BTIs) are investigated for n- and p-substrate 4H-SiC metal–oxide–semiconductor (MOS) capacitors. The midgap voltage (V \rm mg) shifts positively under positive bias stress at high temperatures for n-substrate capacitors with 67.5-nm nitrided oxides and shifts negatively under negative bias for p-substrate capacitors with 55-nm nitrided oxides. The magnitudes of the Vmg shifts are less than 0.5 V for electric fields of magnitudes of approximately \pm3.1 MV/cm for up to one day of stress at 150 ^\circ\C or 20 min of stress at 300 ^\circ\C. Switched-bias stressing at 150 ^\circ\C causes partially reversible shifts for the n-substrate capacitors, while the p-substrate capacitors show monotonically increasing negative shifts. Based on the measured temperature dependence of the Vmg shifts, the effective activation energy for BTI that is measured between room temperature and 250 ^\circ\C is 0.12 \pm 0.02 eV for the n-substrate capacitors (positive shifts) and 0.23 \pm 0.02 eV for the p-substrate capacitors (negative shifts). The midgap voltage shifts in these wide-bandgap devices are caused by charge capture at deep interface traps and N-related defects at or near the \SiC-\SiO2 interface, which can be enhanced at elevated temperatures by the generation of additional carriers due to the ionization of deep dopants in the SiC during bias-temperature stress. [ABSTRACT FROM PUBLISHER]

Enhanced rates of oxide growth have been observed on silicon upon exposure to 10-keV X-ray irradiation. Oxide thicknesses were determined using spectroscopic ellipsometry on irradiated and control samples, and confirmed via X-ray photoelectron spectroscopy. The oxidation rate varied with the radiation total dose and dose rate. The increased oxidation rate is attributed to the generation of ozone, which decomposes into molecular oxygen and highly reactive atomic oxygen at the surface of the Si wafer. The generation of ozone by 10-keV X-rays was found to increase linearly with increasing dose rate. UV irradiation led to similarly enhanced oxidation rates. The potential application of this phenomenon to dosimetry is explored. [ABSTRACT FROM AUTHOR]

Irradiated Ge pMOSFETs have been characterized via charge pumping (ICP) and 1/f noise. The noise increases much more with irradiation than does ICP for devices with eight Si monolayers at the interface, while devices with five Si monolayers and lower halo implantation dose exhibit comparable increases in noise and ICP with irradiation. These results suggest that border traps in the HfO2 affect the noise more than interface traps, and that devices with eight Si monolayers have a higher border-trap density than devices with five Si monolayers. Noise measurements as a function of gate voltage show that the border trap density increases significantly toward the Ge valence band edge, while three-level charge pumping reveals an interface trap density that increases slightly toward midgap. [ABSTRACT FROM AUTHOR]

The irradiation and annealing responses of Ge pMOSFETs have been investigated under transmission gate bias. Both the radiation-induced charge trapping and the low frequency (1/ f ) noise increase with total ionizing dose and decrease with annealing time. The smallest increases in noise after irradiation are observed for Ge pMOSFETs with the lowest halo implantation doses. The smallest increases in oxide and interface trap charge densities are obtained for devices with eight monolayers of Si at the interface, as compared to devices with five Si monolayers. [ABSTRACT FROM AUTHOR]