Enhanced Low Dose Rate Sensitivity Research Articles

How the Analysis of Archival Data Could Provide Helpful Information About TID Degradation. Case Study: Bipolar Transistors

A critical step of radiation hardness assurance (RHA) for space systems is given by the parts selection in accordance with the observed (or estimated) radiation effects. Although radiation testing is the most decisive way of studying the radiation degradation of electronic components, the increasing use of commercial off-the-shelf (COTS) devices and the challenges posed by <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">NewSpace</i> are pushing the need of finding new approaches to assess the risk associated with radiation environments. This work tries to evaluate if valuable information might be extracted from archival data to carry out this assessment despite the well-known and dramatic lot-to-lot, or even part-to-part, variability for some technologies and the impact of the different test conditions, such as the bias conditions and the dose rate in enhanced low dose rate sensitivity (ELDRS). These factors are briefly analyzed for some examples. A new radiation database is briefly introduced, and some statistical approaches are cited, apart from the analysis herein followed. To finish, a first analysis on three families of bipolar transistors is presented together with the independent results from three external reports, with a good agreement between the experimental results and the expected ones.

The Effect of the Ionizing Radiation Intensity on the Response of MOS Structures

The effect of the intensity of ionizing radiation on the volume charge and surface-state density of metal—oxide—semiconductor (MOS) structures with thin gate silicon dioxide is modeled. It is shown that the dependences of the surface-state density and volume charge on the total time of ionizing radiation and subsequent annealing at different ionizing-radiation intensities lie on the corresponding common curves Nit(t) and Qot(t). The Nit(t) common curve is determined by the dispersive nature of the transport of hydrogen ions Н+. The observed deviations from this Nit(t) common curve immediately after the end of ionizing irradiation are due to the transient process of the redistribution of Н+ ions. The Qot(t) common curve is determined by relaxation of the volume charge from a system of levels with energies of 0.3 to 1.0 eV by the mechanism of thermal emission. It is shown that the enhanced low-dose-rate sensitivity (ELDRS) for the MOS structures with a thick base oxide at low intensities is determined by the dispersive character of the transport of hydrogen ions Н+.

A modified accelerated testing method of ELDRS in extreme-low dose rate irradiation

Low dose rate radiation induced gain degradation in bipolar devices is considered to be the primary threat to the spacecraft reliability and service life. In order to examine the radiation tolerance of bipolar devices, it is recommended to use 10 m rad(Si)/s as the typical dose rate in the standards MIL-STD-883G. There is lack of solid study to prove the dose rate is sufficient enough low. Our latest experiment results showed that the enhanced low dose rate sensitivity (ELDRS) effects was not saturated at 10 m rad(Si)/s. To examine the reliability of bipolar devices in extreme low dose rate environment below 10 m rad(Si)/s in short time, we proposed a modified accelerated testing method of ELDRS effects in extreme-low dose rate irradiation based on elevated temperature irradiation and temperature-switching during irradiation, which is helpful to get quantified results in the whole low dose rate range.

Enhanced Low-Neutron-Flux Sensitivity Effect in Boron-Doped Silicon.

Space particle irradiation produces ionization damage and displacement damage in semiconductor devices. The enhanced low dose rate sensitivity (ELDRS) effect caused by ionization damage has attracted wide attention. However, the enhanced low-particle-flux sensitivity effect and its induction mechanism by displacement damage are controversial. In this paper, the enhanced low-neutron-flux sensitivity (ELNFS) effect in Boron-doped silicon and the relationship between the ELNFS effect and doping concentration are further explored. Boron-doped silicon is sensitive to neutron flux and ELNFS effect could be greatly reduced by increasing the doping concentration in the flux range of 5 × 109–5 × 1010 n cm−2 s−1. The simulation based on the theory of diffusion-limited reactions indicated that the ELNFS in boron-doped silicon might be caused by the difference in the concentration of remaining vacancy-related defects (Vr) under different neutron fluxes. The ELNFS effect in silicon becomes obvious when the (Vr) is close to the boron doping concentration and decreased with the increase in boron doping concentration due to the remaining vacancy-related defects being covered. These conclusions are confirmed by the p+-n-p Si-based bipolar transistors since the ELNFS effect in the low doping silicon increased the reverse leakage of the bipolar transistors and the common-emitter current gain (β) dominated by highly doped silicon remained unchanged with the decrease in the neutron flux. Our work demonstrates that the ELNFS effect in boron-doped silicon can be well explained by noise diagnostic analysis together with electrical methods and simulation, which thus provide the basis for detecting the enhanced low-particle-flux damage effect in other semiconductor materials.

Enhanced low dose rate sensitivity (ELDRS) and reduced low dose rate sensitivity (RLDRS) in bipolar devices

Possible physical mechanism of enhanced low dose rate sensitivity (ELDRS) and reduced low dose rate sensitivity (RLDRS) in bipolar devices is described. Modification of the low dose rate conversion model is presented. The enhanced or reduced sensitivity can be connected with a specific position of the effective Fermi level relatively acceptor and donor radiation-induced interface traps. The qualitative and quantitative analysis of the low dose rate effects is presented. The effect of the oxide trapped charge on the value of the oxide electric field and the yield of the oxide charge were taken into account. It leads to dependence of the accumulation of radiation induced oxide charge and interface traps on the dose rate. In enhancement version the ELDRS and RLDRS conversion model describes the low dose rate effect in as ?true? dose rate effect.

Comparison of holes trapping and protons transport induced by low dose rate gamma radiation in oxide on different SiGe processes

Space-related electronics contain different types of oxide isolations which are the crucial factor resulting in device degradation and failure. Previous studies show that the local oxidation of silicon (LOCOS) isolation Silicon‑germanium heterojunction bipolar transistor (SiGe HBT) experience more significantly low dose rate sensitivity than that of shallow trench (STI) isolation SiGe HBTs and behave a “true” dose rate effect. In our work, the electron-hole pairs (EHPs) generation, holes trapped and protons transport inside oxide are simulated in LOCOS and STI isolation SiGe HBTs to explanation the different response t enhanced low dose rate sensitivity (ELDRS). The simulation results show that LOCOS oxide has a larger generation of EHPs than that of STI oxide leading to more surviving holes and protons release within oxide.

Using a Temperature-Switching Approach to Evaluate Low-Dose-Rate Ionizing Radiation Effects on SET in Linear Bipolar Circuits

In this paper, a temperature-switching approach (TSA) was used to evaluate low-dose-rate (LDR) ionizing radiation effects on single-event transients (SETs) in linear bipolar circuits. The experimental results show that the SET phenomenon of bipolar circuits after irradiation using a TSA with 3-rad(Si)/s dose rate is basically consistent with the SET phenomenon of bipolar circuits after LDR of 0.01-rad(Si)/s irradiation, which is obviously different from the SET phenomenon of bipolar circuits after the high-dose-rate of 10-rad(Si)/s irradiation. The TSA for evaluating the enhanced LDR sensitivity (ELDRS) of bipolar devices can be applied to the rapid evaluation of the SET effect of the bipolar circuits with LDR irradiation.

Mechanism of Degradation Rate on the Irradiated Double-Polysilicon Self-Aligned Bipolar Transistor

The latent enhanced low dose rate sensitivity (ELDRS) effect is observed in the double-polysilicon self-aligned (DPSA) technology PNP bipolar junction transistor (BJT) irradiated with a high and low dose rate gamma ray, which is discussed from the perspective of the three-stage degradation rate of the excess base current. The great degradation rate as a result of the high dose irradiation of the first stage is dominantly ascribed to the positive oxide trap charges accumulated during a short irradiation, and then due to the competition between the recombination of electrons and capture of the hole by the traps. It declined sharply into a degradation rate saturated region of the second stage. However, for the low dose rate, the small increase in the degradation rate in the first stage is caused by the holes escaping from the initial recombination and being transported to the interface to form the interface states. Then, the competition between the steadily increasing interfacial trap charge and the continuously annealed shallow level oxide trap charge leads to the stable increase of degradation under low dose irradiation. Finally, in stage three, the increases of the degradation rates for high and low dose irradiation result from the different amounts of the hydrogen molecules generated by the hole reactive with depassiviated Si suspended bonds, which can interact with the deep level defects and release protons, causing an increase of interfacial trap charges with prolonged irradiation.

Temperature-Switching During Irradiation as a Test for ELDRS in Linear Bipolar Devices

A temperature-switching irradiation (TSI) sequence has been developed that is based on a first-principles understanding of interface-trap buildup and annealing. The dynamics of interface-trap buildup and annealing during elevated temperature irradiation are described in detail to provide background, context, and enhanced understanding of the TSI method. The method is shown to be a practical and conservative test for enhanced low-dose-rate sensitivity (ELDRS) in linear bipolar devices and ICs. Examples of TSI sequences are shown for target doses up to 200 krad(Si), a range of great practical interest for space applications. The method can be adapted for higher dose applications via similar approaches. Devices that do not exhibit ELDRS respond similar to TSI and high-dose-rate irradiation.

Synergistic effect of enhanced low-dose-rate sensitivity and single event transient in bipolar voltage comparator LM139

ABSTRACT The bipolar voltage comparator LM139 were exposed to ionizing radiation with a high-dose-rate of 10 rad(Si)/s and a low-dose-rate of 0.01 rad(Si)/s; then, pulsed laser single-event-transient (SET) testing was performed. The experimental results show that the SET phenomenon of LM139 after low-dose-rate irradiation of 0.01 rad(Si)/s is obviously different from the SET phenomenon of LM139 after high-dose-rate irradiation of 10 rad(Si)/s. After irradiation with the low-dose-rate, the comparator LM139 has Enhanced Low Dose Rate Sensitivity (ELDRS) in terms of the total dose effect, and the SET was further influenced by ELDRS. The greater gain degradation of the internal transistor in LM139 with low-dose-rate irradiation is the direct cause of this phenomenon.

Impact of elevated temperature applied during low dose rate irradiation on the degradation of BiCMOS operational amplifiers

The radiation-induced change in input bias current of bipolar input stage of BiCMOS operational amplifiers susceptible to enhanced low dose rate sensitivity (ELDRS) is studied as a function of the dose rate of gamma-irradiation and of the temperature applied during irradiation. Experimental results and results of the simulation with the conversion model of radiation-induced interface traps formation have shown that degradation enhancement factor KD provided by the temperature applied during irradiation exhibits a nonmonotonic dependence on the dose rate: an elevated temperature provides the maximum increase in the degradation, if the dose rate is chosen from the range 0.1–1 rad(Si)/s, while irradiation with high (≥101 rad(Si)/s) and low dose rate (≤10−2 rad(Si)/s) provides approximately the same values of KD. This range can be recommended for accelerated testing of bipolar and BiCMOS devices, if enhanced degradation in low dose rate conditions of space application is modeled by irradiation at elevated temperature.

Dose-Rate Sensitivity of 65-nm MOSFETs Exposed to Ultrahigh Doses

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.

Estimation of enhanced low dose rate sensitivity mechanisms using temperature switching irradiation on gate-controlled lateral PNP transistor**Project supported by the National Natural Science Foundation of China (Grant Nos. U1532261 and 1630141).

The mechanisms occurring when the switched temperature technique is applied, as an accelerated enhanced low dose rate sensitivity (ELDRS) test technique, are investigated in terms of a specially designed gate-controlled lateral PNP transistor (GLPNP) that used to extract the interface traps (Nit) and oxide trapped charges (Not). Electrical characteristics in GLPNP transistors induced by 60Co gamma irradiation are measured in situ as a function of total dose, showing that generation of Nit in the oxide is the primary cause of base current variations for the GLPNP. Based on the analysis of the variations of Nit and Not, with switching the temperature, the properties of accelerated protons release and suppressed protons loss play critical roles in determining the increased Nit formation leading to the base current degradation with dose accumulation. Simultaneously the hydrogen cracking mechanisms responsible for additional protons release are related to the neutralization of Not extending enhanced Nit buildup. In this study the switched temperature irradiation has been employed to conservatively estimate the ELDRS of GLPNP, which provides us with a new insight into the test technique for ELDRS.

Estimation of low-dose-rate degradation on bipolar linear circuits using different accelerated evaluation methods

The linear bipolar devices and integrated circuits (ICs) which are subjected to ionizing radiation exhibit parametric degradations due to current-gain decrease, and the amount of degradation on various types of bipolar devices is much more significant at low-dose-rate than at high-dose-rate. Such an enhanced low-dose-rate sensitivity (ELDRS) is considered to be one of the major challenges for radiation-tolerance testing intended for space systems. Therefore, it is of great significance to explore an efficient and practical test for the ELDRS in the linear bipolar devices and ICs. The different experiments have been implemented on four types of bipolar ICs for evaluating their responses to low-dose-rate irradiation. The experiments involve the dose rate switching approach performed under high to low-dose-rate irradiation and temperature switching approach performed under high to low temperature irradiation. Good agreement is observed between predictive curves obtained at dose rate switching irradiation and the low-dose-rate results, and the irradiation time for the dose rate switching approach is reduced from 4 months to a week. Further, the results also suggest that the device degradation rate can affect the prediction of the total dose. This is because the curves examined at different doses have a lot of overlap when the devices with fast degradation rates are performed. In addition to temperature switching irradiation, the radiation response of the same type of device is much more significant than that obtained in low-dose rate irradiation, and this method will shorten the irradiation time to 12 h. Based on the analysis of mechanisms behind the switched dose rate and temperature irradiation, switching temperature irradiation can accelerate the release of protons and buildup of interface traps, which is the key physical mechanism for ELDRS. Firstly, a higher irradiation temperature can enhance the transport of holes and release of protons to form interface traps, resulting in the enhanced degradation occurring at first dose examined. Further, the reducing temperature sequence suppresses the hydrogen dimerization process during the irradiation that follows, which is strongly temperature dependent and contributes to interface trap annealing. Moreover, further decrease in temperature can restrict the interface trap annealing because the barrier for this process is higher and it has less opportunity to take place at lower temperature. Additionally, the hydrogen molecules converted from hydrogen dimerization may extend the liberation of protons, by the hydrogen molecules cracking mechanisms, leading to the additional degradation. Therefore, the temperature switching irradiation is shown to be a conservative and efficient method for ELDRS in bipolar devices, and this provides an insight into hardness assurance testing.

An Investigation of ELDRS in Different SiGe Processes

Enhanced low dose rate sensitivity (ELDRS) in different process Silicon–Germanium heterojunction bipolar transistors (SiGe HBTs) is investigated. Low and high dose rate irradiations are performed to evaluate the ELDRS of SiGe HBTs manufactured by Tsinghua University (THU). THU SiGe HBTs experience significantly low dose rate sensitivity than that of IBM 8HP SiGe HBTs and behave a “true” dose rate effect. TCAD models were used to explicate the microcosmic structure in THU and IBM 8HP SiGe HBTs. Comparison and discussion show that different SiGe processes may involve different HBT structures and device designs which are the critical influence of ELDRS effect. The different responses of ELDRS should be first attributed to the device structure and design in nature, particularly the geometry of emitter–base junction and the isolation structure.

ELDRS Susceptibility of Bipolar Transistors and Integrated Circuits During Low Temperature Irradiation

The enhanced low dose rate sensitivity (ELDRS) susceptibility of 2N2222 bipolar transistors and LM111 voltage comparators was investigated during irradiation at low temperature and compared with corresponding room-temperature data. The possible physical mechanism of the ELDRS effect in bipolar transistors and integrated circuits during irradiation at room temperature and low temperature was described. A device that is ELDRS-free at room temperature suffers from this effect during irradiation at low temperature.

Conversion model of radiation-induced interface-trap buildup and the some examples of its application

It is supposed that the rechargeable radiation-induced positive centers in the oxide must have energy levels within the Si forbidden gap. These assumptions served as the basis for the physical model of the interface-trap build-up and enhanced low dose rate sensitivity (ELDRS) in bipolar devices. As examples of using the proposed conversion model is considered for bipolar devices space application.

Total ionizing dose effects of domestic SiGe HBTs under different dose rates

The total ionizing radiation (TID) response of commercial NPN silicon germanium hetero-junction bipolar transistors (SiGe HBTs) produced domestically are investigated under dose rates of 800 mGy(Si)/s and 1.3 mGy(Si)/s with a Co-60 gamma irradiation source. The changes of transistor parameters such as Gummel characteristics, and excess base current before and after irradiation, are examined. The results of the experiments show that for the KT1151, the radiation damage is slightly different under the different dose rates after prolonged annealing, and shows a time dependent effect (TDE). For the KT9041, however, the degradations of low dose rate irradiation is higher than for the high dose rate, demonstrating that there is a potential enhanced low dose rate sensitivity (ELDRS) effect for the KT9041. The possible underlying physical mechanisms of the different dose rates responses induced by the gamma rays are discussed.

Dose-rate sensitivity of deep sub-micro complementary metal oxide semiconductor process

Enhancing low dose rate sensitivity (ELDRS) in bipolar device is a major problem of liner circuit radiation hardness prediction for space application. ELDRS is usually attributed to space-charge effect. A key element is the difference in transport rate between holes and protons in SiO2. Interface-trap formation at high dose rate is reduced due to positive charge buildup in the Si/SiO2 interfacial region (due to the trapping of holes and/or protons) which reduces the flow rates of subsequent holes and protons (relative to the low-dose-rate case) from the bulk of the oxide to the Si/SiO2 interface. Generally speaking, the dose rate of metal oxide semiconductor (MOS) device is time dependent when annealing of radiation-induced charge is taken into account. The degradation of MOS device induced by the low dose rate irradiation is the same as that by high dose rate when annealing of radiation-induced charge is taken into account. However, radiation response of new generation MOS device is dominated by charge buildup in shallow trench isolation (STI) rather than gate oxide as older generation device. Unlike gate oxides, which are routinely grown by thermal oxidation, field oxides are produced using a wide variety of deposition techniques. As a result, they are typically thick (100 nm), soft to ionizing radiation, and electric field is far less than that of gate oxide, which is similar to the passivation layer of bipolar device and may lead to ELDRS. Therefore, dose-rate sensitivities of n-type metal oxide semiconductor field effect transistor (NMOSFET) and static random access memory (SRAM) manufactured by 0.18 m complementary metal oxide semiconductor (CMOS) process are explored experimentally and theoretically in this paper. Radiation-induced leakages in NMOSFET and SRAM are examined each as a function of dose rate. Under the worst-case bias, the degradation of NMOSFET is more severe under the low dose rate irradiation than under the high dose rate irradiation and anneal. Moreover, radiation-induced standby current rising in SRAM is more severe under the low dose rate irradiation than under the high dose rate irradiation even when anneal is not considered. The above experimental results reveal that the dose-rate sensitivity of deep sub-micron CMOS process is not related to time-dependent effects of CMOS devices. Mathematical description of the combination between enhanced low dose-rate sensitivity and timedependent effects as applied to radiation-induced leakage in NMOSFET is developed. It has been numerically found that non time-dependent effect of deep sub-micron CMOS device arises due to the competition between enhanced low dose-rate sensitivity in bottom of STI and time-dependent effect at the top of STI. The high dose rate irradiation is overly conservative for devices used in a low dose rate environment. The test method provides an extended room temperature anneal test to allow leakage-related parameters that exceed postirradiation specifications to return to a specified range.

Quantum Mechanical Modeling of Radiation-Induced Defect Dynamics in Electronic Devices

Density functional theory (DFT) has emerged as a powerful tool to model defect properties and dynamics at the quantum mechanical level. Results from targeted DFT calculations can provide valuable insight into the atomistic nature of radiation-induced defect phenomena in microelectronics. This review describes the foundations of DFT, its implementations, and defect calculations. Illustrative examples from recent studies are presented in which DFT calculations, combined with experiments, have led to new insights into the microscopic processes that lead to the observed radiation response. These include GaN/AlGaN HEMTs, proton-induced interface-trap formation at the Si-SiO2 interface, and the role of hydrogen in enhanced low-dose-rate sensitivity (ELDRS) in bipolar devices and ICs.