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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]

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]

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]

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]

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

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

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

A 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]

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]

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]

Bipolar test structures were irradiated and annealed with various combinations of molecular hydrogen gas ambients, bias, and thermal conditions. The results show that the buildup and annealing behavior of defects in bipolar base oxides depend strongly on hydrogen concentration. Differences observed in trapped oxide charge annealing rates suggest that the charged defects created in hydrogen-rich environments may be attributed to different types of positive charge in addition to trapped holes. [ABSTRACT FROM PUBLISHER]

Transistors and ICs built in several different captive and commercial facilities were exposed to moisture, irradiated, and annealed. The moisture exposures were performed using highly accelerated stress test (HAST) at 130degC and 85% relative humidity. Irradiation of n-channel transistors exposed to HAST followed by a long-term anneal resulted in some increase in interface-trap and oxide-trapped charge buildup. However, exposing p-channel transistors to HAST preirradiation resulted in extremely large and unexpected voltage shifts immediately following irradiation. They were observed for devices with either doped oxide or nitride final chip passivation. Because of this, nitride passivation may not be sufficient to prevent H2O from causing enhanced radiation-induced degradation over long time periods in some devices (e.g., commercial devices with nitride final chip passivation packaged in plastic packages). The smaller voltage shifts for the n-channel transistors may be related to the formation of phosphosilicate glass (PSG) overlying the sources and drains of the n-channel transistors impeding the diffusion of moisture to the gate oxides. It is shown that, the large radiation-induced voltage shifts for the p-channel transistors can lead to enhanced IC parametric degradation and functional failure at lower radiation levels. Large increases in radiation-induced field oxide leakage current were also observed for transistors exposed to HAST preirradiation. Transistors were also annealed (prior to irradiation) and irradiated in H2. Approximately the same level of radiation-induced degradation was observed for n- and p-channel transistors suggesting that the diffusion kinetics for H2 diffusion are considerably different than for H2O diffusion. These results raise the concern that exposure of devices to moisture or hydrogen can lead to long-term radiation-induced aging effects. [ABSTRACT FROM PUBLISHER]

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]

Single event latchup (SEL) in a 65 nm CMOS technology is examined with respect to strike angle of incidence and variations in device temperature. A significant difference in device sensitivity is observed with a change in the orientation of grazing angle strikes. The impact of an extremely high aspect ratio sensitive volume on SEL rate is discussed. It is suggested that SEL experiments should be conducted at various lateral orientations when near-grazing beam angles are tested. [ABSTRACT FROM AUTHOR]

We investigate the effects of both X-ray and proton irradiation on a novel 200 GHz/90 GHz (npn/pnp) complementary SiGe:C HBT technology. The dc forward mode total dose tolerance of the pnp HBTs is shown to exceed that of the npn HBTs by a significant margin after being subjected to both 63-MeV proton and 10-key X-ray sources, while the ac characteristics of both devices exhibit no degradation up to X-ray doses as high as 1.8 Mrad(SiO2). Pre- and post-irradiation results from a current feedback operational amplifier implemented in this technology and irradiated up to a dose of 1.8 Mrad(SiO2) are presented, showing no degradation in performance metrics under two low current density bias configurations. [ABSTRACT FROM AUTHOR]

The radiation tolerance of strained Si/SiGe n-MODFETs is investigated, using 10 keV X-rays, 63 MeV high energy protons, and 4 MeV low energy protons. The effects of radiation exposure on two major device design parameters (LSD and LG) in T-gate Si/SiGe n-MODFETs devices are examined. A strong dependence on source-drain spacing is observed for both the DC and RF characteristics. A drift-diffusion TCAD framework is used for 2-D device simulations. We believe that the low energy protons damage the SiGe/strained-Si/SiGe lattice, leading to partial strain relaxation. The conduction band-offset (CBO) of the strained SiGe/Si heterojunction is lowered leading to higher gate current leakage. The presence of radiation-induced bulk traps in the unrelaxed SiGe layers on the device behavior is also investigated. [ABSTRACT FROM AUTHOR]

The impact of 63.3 MeV proton and 10 keV x-ray irradiation on the DC and AC performance of complementary (npn + pnp) SiGe HBTs on thick-film SOI is investigated. Proton and x-ray induced changes in the forward and inverse Gummel characteristics, the output characteristics, and avalanche multiplication are reported for both npn and pnp SiGe HBTs, at both room temperature (300 K) and at cryogenic temperatures (down to 30 K). Comparison of room temperature and cryogenic data suggests interface trap formation at two distinct physical locations in the transistors. Experimental data and calibrated TCAD simulations are used to compare the radiation response of both thick-film SOI devices and thin-film SOI SiGe HBTs. [ABSTRACT FROM AUTHOR]

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]

We examine the limits of performing single-event simulations using pre-averaged radiation events. Geant4 simulations show the necessity, for future devices, to supplement current methods with ensemble averaging of device-level responses to physically realistic radiation events. Initial Monte Carlo simulations have generated a significant number of extremal events in local energy deposition. These simulations strongly suggest that proton strikes of sufficient energy, even those that initiate purely electronic interactions, can initiate device response capable in principle of producing single event upset or microdose damage in highly scaled devices. [ABSTRACT FROM AUTHOR]