Total Ionizing Dose Radiation Research Articles

Impact of TID on Within-Wafer Variability of Radiation-Hardened SOI Wafers

Impact of total ionizing dose (TID) on the within-wafer variability of radiation-hardened (RH) silicon-on-insulator (SOI) wafers is investigated in this article. The within-wafer variability is measured by the front gate and back gate <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V$ </tex-math></inline-formula> characteristics of the transistors in 32 dies evenly distributed on wafer locations. The experimental results show the complex dependence of the within-wafer variability on TID: the within-wafer variability of RH SOI wafer is first weakened by TID irradiation and then rebounds. The evolution of net trapped charge induced by TID in buried oxide (BOX) is affected by positively charged silicon nanoclusters introduced by silicon ion implantation, which is responsible for the above complex dependence. Moreover, radiation hardness assurance method relying on sample testing of limited wafer locations is discussed, which can give the reasonable estimation of the within-wafer variability on TID irradiated devices.

Influence of enhanced low dose rate sensitivity on single-event transient degradation in the LM158 bipolar operational amplifier

The synergistic effect of enhanced low dose rate sensitivity and single-event transients (SETs) in the bipolar dual operational amplifier LM158 is studied. The test results show a significant reduction in the SET amplitude and broadening in the SET waveform upon exposure to total ionizing dose radiation. These results are much more prominent for a low dose rate (LDR) irradiation of 0.01 rad(Si)/s than for a high dose rate irradiation of 10 rad(Si)/s. The greater gain degradation in the LM158 with LDR irradiation could be the direct cause of the reduction in the SET amplitude and broadening in the SET waveform, and this is corroborated through HSPICE simulations.

Improving TID Radiation Robustness of a CMOS OxRAM-Based Neuron Circuit by Using Enclosed Layout Transistors

Aerospace applications are attractive candidates to embed artificial neural networks despite their excellent parallel processing capability and reduced energy consumption. Nonetheless, the long-term exposure to incidence levels of ionizing radiation may degrade their physical components reducing, therefore, their reliability and expected lifetime. Thus, it is mandatory to face the challenge of enhancing the radiation hardening characteristics of a neural circuit before operating in harsh environments. A possible solution to substantially reduce long-term spurious effects caused by ionizing radiation [referred to as total ionizing dose (TID)] is to change the conventional rectangular MOS gate geometry to a nonstandard topology referred to as an enclosed layout transistor (ELT). In the context of hardening a complete neuron circuit against TID effects, together with the well-established ELT paradigm, it is possible to exploit the inclusion of other hardened devices, for instance, the memory element. In this sense, the Oxide-based Resistive Random Access Memory (OxRAM) can be used as the memory element, which is inherently tolerant against ionizing radiation and, hence, better suited for a fully hardened circuit. In this work, we propose to harden the design of an existing OxRAM-based neuron circuit through the inclusion of ELTs, i.e., to improve the radiation hardening characteristics of a preexistent convenient neuron circuit topology by using the enclosed gate geometry for the nMOS and pMOS devices. Electrical simulations, considering a standard commercial bulk CMOS fabrication process, in a 180-nm technology, have been carried out to validate our proposed design. In addition, we exploit two simulation setups: first, the OxRAM's behavior in a simple circuit configuration, to provide a better understanding of the OxRAM device; second, the OxRAM-based neuron circuit, to evaluate the behavior of the proposed neuron circuit hardened with ELTs. The simulation results, supported by the analysis of former works regarding the incidence of ionizing radiation in OxRAM and ELTs, indicate that the proposed hardened neuron circuit is a feasible solution to embed neuromorphic computing in aerospace applications.

Applications of Direct-Current Current–Voltage Method to Total Ionizing Dose Radiation Characterization in SOI NMOSFETs with Different Process Conditions

As a promising candidate in space radiation hardened applications, silicon-on-insulator (SOI) devices face the severe problem of total ionizing dose (TID) radiation because of the thick buried oxide (BOX) layer. The direct-current current–voltage (DCIV) method was applied for studying TID radiation of SOI metal–oxide–semiconductor field–effect transistors (MOSFETs) with different manufacture processes. It is found that the peak of high-voltage well (PX) devices shows a larger left-shift and a slower multitude increase along with radiation dose, compared with that of low-voltage well (PV) devices. It is illustrated that the high P-type impurity concentration near back interface makes it more difficult to break up silicon hydrogen bonds, which gives the PX devices superiority in resisting the build-up of interface traps. The study results indicate that increasing doping concentration of the body region near the back-gate interface might be an alternative radiation hardening technique of SOI MOSFET devices to avoid the parasitic back transistors’ leakage.

Impacts of Through-Silicon Vias on Total-Ionizing-Dose Effects and Low-Frequency Noise in FinFETs

Total-ionizing-dose (TID) effects and low-frequency noise are evaluated in advanced bulk nMOS and pMOS FinFETs with SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ). TSV integration negligibly impacts threshold shifts and degradation of subthreshold swing and I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OFF</sub> 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.

Research on Negative Bias Temperature Instability Effects Under the Coupling of Total Ionizing Dose Irradiation for PDSOI MOSFETs

The degradation mechanisms for pMOSFETs from a 130 nm partially-depleted silicon on insulator (PDSOI) technology under the combined effects of total ionizing dose (TID) and negative bias temperature instability (NBTI) are investigated. The TID and NBTI related degradations show an opposite trend as gate oxide scaling, which implies the different traps are activated during irradiation and NBTI stress. The radiation-induced traps can affect the NBTI effect of pMOSFET, especially for the ON bias irradiation. The irradiated I/O pMOSFET shows a smaller threshold voltage shift than the un-irradiated device under the same NBTI stress at the early stress stage. It may be contributed to the enhanced Fowler-Nordheim electron injection during NBTI stressing after ON bias irradiation. But the irradiation also increases the time exponent $n$ from 0.11 to 0.13 for Core pMOSFETs and from 0.18 to 0.20 for I/O devices. It means that the NBTI degradations become worse after ON bias irradiation in a long time scale. This phenomenon is attributed to the change of trap characteristics caused by irradiation. As a result, the NBTI lifetime of Core device is reduced by nearly three orders of magnitude and the lifetime of I/O device is reduced by five times after ON bias irradiation at the rated operating voltage.

Experimental investigation on total-ionizing-dose radiation effects on the electrical properties of SOI-LIGBT

In this paper, the experimental investigation on the electrical properties of silicon-on-insulator lateral insulated-gate bipolar transistor (SOI-LIGBT) after total-ionizing-dose (TID) irradiation is presented. We find that the TID irradiation reduces the threshold voltage (Vth), and increases the collector current (ICE) at the same gate voltage (Vg). The raising ICE is mainly attributed to the negative shift of the Vth. However, at the same overdrive voltage (Vov = Vg − Vth), the ICE at small VCE increases and the ICE at high VCE decreases after irradiation. The distinctive response of the out-put characteristics after irradiation is ascribed to the positive trapped charges in the field oxide (FOX) layer and the buried oxide (BOX) layer. The inimitable out-put behavior occurs at whatever the sign of the gate bias voltage during irradiation. The degradation mechanisms of the TID effects on the SOI-LIGBT are further analyzed and confirmed by simulation.

Experimental results on diodes and BIMOS ESD devices in 28 nm FD-SOI under TLP & TID radiation

The electrostatic discharge (ESD) protection is a major concern for advanced CMOS technology manufacturing. Several solutions are available on market with efficient robustness and compliant with the ESD window especially in 28 nm FD-SOI technology. In the framework of harsh environment applications and to explore the performance under total ionizing dose (TID) radiation, it is important to investigate ESD protection devices such as gated and STI diodes in hybrid bulk or BIMOS solution in thin silicon film. This study is based on transmission line pulse (TLP) characterization before and after Co60 TID radiation in the range of [25 krad–200 krad]. This dose range is chosen for a first robustness exploration and in link with product applications. Following this analysis, we expect to gain better understanding of robustness and push the final performance of the device. The preliminary results will be useful to give a trend and to improve the device robustness against ESD and TID events and lead to more competitive solutions.

The effects of Total Ionizing Dose irradiation on supercapacitors deployed in nuclear decommissioning environments

The effects of Total Ionizing Dose (TID) on electrical components is a key parameter to evaluate the life span of wireless sensor nodes for possible deployment in nuclear decommissioning environments. The aim of this study was to experimentally evaluate the effects of TID on capacitance, internal resistance and the self-discharge characteristic of 100 F supercapacitors. An automated test circuit was designed and assembled to charge and discharge the supercapacitors. The supercapacitors were irradiated using a Co-60 γ ray radiation source and the voltage across the supercapacitor terminals, charging current and discharging current were monitored and logged to calculate the capacitance during the irradiation process. Measurements of internal resistance and self-discharge characteristic were performed before and after the irradiation to examine the effects of exposure to γ radiation on these electrical properties. The experimental results show negligible effects on the capacitance of supercapacitors exposed to a maximum dose of 40 kGy. The internal resistance and self-discharge characteristics were not affected by TID up to 89 kGy. These results demonstrate that supercapacitors are a suitable technology to design an Energy Storage System to be deployed in the majority of nuclear decommissioning environments.

Radiation-hardened and repairable integrated circuits based on carbon nanotube transistors with ion gel gates

Electronics devices that operate in outer space and nuclear reactors require radiation-hardened transistors. However, high-energy radiation can damage the channel, gate oxide and substrate of a field-effect transistor (FET), and redesigning all vulnerable parts to make them more resistant to total ionizing dose irradiation has proved challenging. Here, we report a radiation-hardened FET that uses semiconducting carbon nanotubes as the channel material, an ion gel as the gate and polyimide as the substrate. The FETs exhibit a radiation tolerance of up to 15 Mrad at a dose rate of 66.7 rad s−1, which is notably higher than the tolerance of silicon-based transistors (1 Mrad). The devices can also be used to make complementary metal–oxide–semiconductor (CMOS)-like inverters with similarly high tolerances. Furthermore, we show that radiation-damaged FETs can be recovered by annealing at a moderate temperature of 100 °C for 10 min. By using carbon nanotubes as a channel material, an ion gel as a gate and polyimide as a substrate, field-effect transistors can be created that have a high radiation tolerance and can be repaired by annealing.

Effects of TID radiation on P+ ion-implanted HVNMOS devices

This paper studied the effect of total ionizing dose (TID) radiation on 10 V high-voltage n-type metal-oxide-semiconductor (HVNMOS) devices. The study was conducted on two devices with P+ ion-implantation for radiation-hardening. Both devices were geared towards embedded applications, and ions were implanted into them through P+ ring and P+ sub implantation methods, separately. Leakage channels induced by TID radiation were analyzed to identify key leakage paths. Gate modulation effects, caused by P+ implantation in HVNMOS devices, were studied through gate voltage and junction voltage from drain/source (D/S) to substrate (B). It was uncovered that P+ ring ion implantation was most suitable for radiation-hardening in HVNMOS devices with TID irradiation of over 150 K rad (Si).

Bias and geometry dependence of total-ionizing-dose effects in SOI FinFETs

In this paper, a systematic research on the total-ionizing-dose (TID) effects of NMOS and PMOS silicon-on-insulator (SOI) FinFETs is performed experimentally. The bias and geometry dependence of TID effects are analysed. The experimental results show that the threshold voltage (Vth) shift occurs in SOI FinFETs after x-ray irradiation. After 1 Mrad(Si) irradiation, the maximum Vth shift is about 40 mV. The ‘worst case’ irradiation bias conditions for NMOS and PMOS are TG and ON states, respectively, which induces the largest Vth shift after irradiation. The 3D TCAD simulation is carried out to further analyse the bias dependence results. Simulation results highlight the difference in electric field distribution in the buried oxide under different bias configurations, which leads to different distribution of irradiation-induced trapped charges. Finally, clear geometry dependence is observed in the TID experiment. Both NMOS and PMOS devices with larger fin width and/or smaller gate length are more sensitive to TID irradiation. The results deepen the understanding of the TID effect of SOI FinFETs and provide important technical support for the radiation-hardened research of FinFET technology.

High Displacement Damage Dose Effects in Radiation Hardened CMOS Image Sensors

CMOS image sensors (CISs) hardened by design against total ionizing dose (TID) are exposed to neutron fluences beyond 1014 n(1 MeV)/cm2. Neutron-irradiated devices show a huge increase in the dark current affecting uniformly the pixel array which leads to Gaussian shape dark current distributions. Moreover, random telegraph signal behavior is hardly detectable at these very high neutron fluences since the fluctuation amplitudes are hidden by the dark current shot noise. It is observed that neutrons induce a change in the depleted volume in impacted photodiodes because of doping profile modifications which are responsible for the decrease in the charge-to-voltage conversion factor and quantum efficiency. Even if neutron-induced degradations affect all the image sensor performances, results show that this technology is still functional after having absorbed $8.1\times 10^{14}$ n(1 MeV)/cm2. Image sensors are still able to capture an image without significant degradation compared to nonirradiated devices. Such TID radiation-hardened CISs are thus highly promising for applications where both high TID and high neutron fluence radiation tolerance are required.

Scanner thoracique chez l’enfant atteint de mucoviscidose : intérêt d’un protocole en expiration séquentielle pour réduire la dose d’irradiation

Chest computed tomography (CT) is essential to monitor lung disease in children with cystic fibrosis, but it involves recurrent exposure to ionizing radiation. The aim of this study was to compare the current complete CT protocol (volumetric end-inspiratory plus sequential expiratory acquisition) to a sequential expiratory acquisition protocol alone in terms of image analysis and ionizing radiation dose. Seventy-eight CT scans from 57 children aged 5 to 18 years old were scored on the complete protocol images and on the expiratory sequential images only. Each CT protocol was scored independently, using the Brody scoring system, by two paediatric radiologists. Correlations between the Brody global scores of the two different CT protocols were very good (r=0.90 for both observers), for the bronchiectasis score (r=0.72 and 0.86), mucus plugging score (r=0.87 and 0.83), and expiratory trapped air (r=0.96 and 0.92). Total ionizing radiation dose was reduced, with the measured dose length product (DLP) reduced from 103.31mGy.cm (complete protocol) to 3.06mGy.cm (expiratory protocol) (P<0.001). An expiratory chest CT protocol was accurate in diagnosing early signs of CF disease and permitted significant reduction of radiation dose. This protocol would allow spacing out of complete CT scanning with its higher radiation dose and should be considered for the monitoring of lung disease severity in children with CF.

The TID Characteristics of a Radiation Hardened Sense-Switch pFLASH Cell

In this paper, the total ionizing dose (TID) effects of the Sense-Switch pFLASH cell consisting of sense (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> ) and switch (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) co-floating gate pFLASH transistors fabricated with a 0.13 μm eFLASH technology are studied. Firstly, the impact of TID effects on the programming/erasing state's characteristics of T1and T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> transistors are mainly analyzed though Current-Voltage (I-V) and Transconductance-Voltage (Gm-V) curves. Secondly, the re-programming/erasing state's characteristics of the pFLASH device after TID irradiation, and its threshold voltage, sub-threshold swing, maximum transconductance and other parameters are thoroughly investigated. Lastly, it can be concluded that the threshold voltage of T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> transistors is mainly determined by the changes of floating gate charge (i.e., programming state: electron emission and hole injection; erasing state: electron injection and hole emission), trap charge concentration in oxide layers around floating gate (Not) and trap charge concentration in the interface trap of tunnel oxide (Nit). Meanwhile, the absolute values of the programming and erasing threshold voltage of T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> transistors decrease linearly with the cumulative dose, and the change rates are about 2.25 mV/rad (Si) and 1.45 mV/rad (Si), respectively. In addition, the charge change of floating gate under the ionizing radiation can be compensated by re-programming and re-erasing, but the charge of Nit and Not will increase with the increase of cumulative dose.

Study of the influence of gamma irradiation on long-term reliability of SiC MOSFET

ABSTRACTA study on the long-term reliability of SiC MOSFET in different operating biases under total ionizing dose radiation environment was carried out. The relationship between radiation-induced degradation of electrical parameters and time-dependent dielectric breakdown characteristics was analyzed through the energy band theory and feedback runaway model.

Simulation of Total Ionizing Dose (TID) Effects Mitigation Technique for 22 nm Fully-Depleted Silicon-on-Insulator (FDSOI) Transistor

Based on 22 nm ultrathin-body fully depleted silicon-on-insulator (UTB-FDSOI) transistors, we propose a novel structure of buried insulator layer aiming at total ionizing dose (TID) effects mitigation. Using technology computer-aided design (TCAD) tools, we focus on the influences of UTB-FDSOI devices with different structures and parameters on TID effects, such as buried oxide (BOX) layer thickness, buried Si3N4 layer, and electron traps. First, we construct four types of UTB-FDSOI N-type metal-oxide semiconductor (NMOS) devices numerically, in which the novel device features a buried silicon-oxide-nitride-oxide-silicon (SONOS) structure. Then, the transfer characteristics and trapped charge distribution of these devices are studied under different irradiation doses. It is known that a thinner BOX layer could lead to slighter TID effects, and the buried nitride layer and the electron traps could reduce the TID-induced leakage current ( $\text{I}_{\mathrm {off}}$ ). Employing these optimization structures for TID effects hardness, the innovative transistor shows much better resistance against TID effects compared to the conventional FDSOI transistors. In addition, the threshold voltage of the novel device could be increased by applying appropriate bias conditions, similar to those of programming SONOS memory, so that the $\text{I}_{\mathrm {off}}$ caused by TID irradiation further decreases. These results provide useful guidance for designers to achieve TID effects mitigation of SOI devices.

Ionizing radiation tolerance of stacked Si3N4-SiO2 gate insulators for power MOSFETs

The total ionizing dose radiation response of metal-nitride-oxide-semiconductor capacitors are examined. Capacitors with different oxide and nitride thickness combinations are fabricated and irradiated using a Co-60 gamma source. Electrical characterization showed all samples with oxide/nitride stack gate insulators exhibited significantly higher tolerance to irradiation when compared to metal-oxide-semiconductor capacitors. Thick oxide-nitride layers can be used as gate insulators in power metal-oxide-semiconductor field effect transistors. Technology computer-aided design simulations are performed to characterize the radiation effects mechanisms. Spatially distributed interface traps at shallow energy level were present in all the oxide/nitride stacks. These interface traps decrease as total dose increases. This result may be due to radiation induced hydrogen passivation.

A novel body-on-insulator (BOI) FinFET with excellent TID tolerance and scaling capability

In this paper, the total ionizing dose (TID) response of body-on-insulator (BOI) FinFETs is investigated and compared with bulk Si FinFETs by 3D TCAD simulation. The irradiation induced off-state leakage current (Ioff) is significantly reduced by the localized oxide layer in the sub-fin region of BOI FinFETs. The Ioff of BOI FinFETs increases negligibly after irradiation. In contrast, the Ioff of bulk Si FinFETs with the same geometry increases by several times after irradiation. Besides, BOI FinFETs show weaker dependence on fin width, and the off-state leakage current of bulk FinFETs induced by TID irradiation increases significantly with the decrease of fin width. Moreover, with the scaling of gate length, the Ioff of BOI FinFETs remains almost unchanged, while it increases by more than an order of magnitude for bulk FinFETs, which indicates that BOI FinFETs show strong scaling capability in terms of TID. Therefore, BOI FinFETs demonstrate strong TID tolerance and scaling capability, and have great potential for application in radiation environment.

The total ionizing dose effects of X-ray irradiation on graphene/Si Schottky diodes with a HfO2 insertion layer

The total ionizing dose (TID) effects of X-ray irradiation on graphene/HfO2/Si (Gr/HfO2/Si) Schottky diodes were investigated. The I-V characteristics were studied in detail with different bias conditions during TID irradiation. An increase in the ideality factor and decrease in the Schottky barrier height were observed. Compared with traditional graphene/Si (Gr/Si) Schottky structures, the degradation of electrical characteristics can be effectively suppressed by adding a HfO2 insertion layer between graphene and the Si substrate.