Total Ionization Dose Effects on Charge Storage Capability of Al2O3/HfO2/Al2O3-Based Charge Trapping Memory Cell

Because of the discrete charge storage mechanism, charge trapping memory（CTM） technique is a good candidate for aerospace and military missions. The total ionization dose（TID） effects on CTM cells with Al2O3/HfO2/Al2O3（AHA） high-k gate stack structure under in-situ 10 keV x-rays are studied. The C-V characteristics at different radiation doses demonstrate that charge stored in the device continues to be leaked away during the irradiation,thereby inducing the shift of flat band voltage（V（fb））. The dc memory window shows insignificant changes, suggesting the existence of good P/E ability. Furthermore, the physical mechanisms of TID induced radiation damages in AHA-based CTM are analyzed.

Total Ionizing Dose Radiation Effects on MOS Transistors with Different Layouts

Both nMOS and pMOS transistors with two-edged and multi-finger layouts are fabricated in a standard commercial 0.6μm CMOS/bulk process to study their total ionizing dose （TID） radiation effects. The leakage current, threshold voltage shift, and transconductance of the devices are monitored before and after T-ray irradiation. Different device bias conditions are used during irradiation. The experiment results show that TID radiation effects on nMOS devices are very sensitive to their layout structures. The impact of the layout on TID effects on pMOS devices is slight and can be neglected.

Machine learning-based analyses for total ionizing dose effects in bipolar junction transistors

Machine learning methods have proven to be powerful in various research fields.In this paper,we show that research on radiation effects could benefit from such methods and present a machine learning-based scientific discovery approach.The total ionizing dose(TID)effects usually cause gain degradation of bipolar junction transistors(BJTs),leading to functional failures of bipolar integrated circuits.Currently,many experiments of TID effects on BJTs have been conducted at different laboratories worldwide,producing a large amount of experimental data which provides a wealth of information.However,it is difficult to utilize these data effectively.In this study,we proposed a new artificial neural network(ANN)approach to analyze the experimental data of TID effects on BJTs An ANN model was built and trained using data collected from different experiments.The results indicate that the proposed ANN model has advantages in capturing nonlinear correlations and predicting the data.The trained ANN model suggests that the TID hardness of a BJT tends to increase with base current I.A possible cause for this finding was analyzed and confirmed through irradiation experiments.

Synergistic effect of total ionizing dose on single event effect induced by pulsed laser microbeam on SiGe heterojunction bipolar transistor

The synergistic effect of total ionizing dose（TID） on single event effect（SEE） in SiGe heterojunction bipolar transistor（HBT） is investigated in a series of experiments. The SiGe HBTs after being exposed to 60 Co g irradiation are struck by pulsed laser to simulate SEE. The SEE transient currents and collected charges of the un-irradiated device are compared with those of the devices which are irradiated at high and low dose rate with various biases. The results show that the SEE damage to un-irradiated device is more serious than that to irradiated SiGe HBT at a low applied voltage of laser test. In addition, the g irradiations at forward and all-grounded bias have an obvious influence on SEE in the SiGe HBT, but the synergistic effect after cutting off the g irradiation is not significant. The influence of positive oxide-trap charges induced by TID on the distortion of electric field in SEE is the major factor of the synergistic effect. Moreover, the recombination of interface traps also plays a role in charge collection.

Synergistic effects of total ionizing dose and radiated electromagnetic interference on analog-to-digital converter

The influence of combined total ionization dose(TID)and radiated electromagnetic interference(EMI)in a commercial analog-to-digital converter(ADC)was studied.The degradation of the direct-current response,the static parameters,and the dynamic parameters caused by the TID and EMI separately and synergistically is presented.The experimental results demonstrate that the increase in TID intensifies data error and the signal-tonoise ratio(SNR)degradation caused by radiated EMI.The cumulative distribution function of EMI failure with respect to data error and SNR with different TIDs was extracted.The decreasing trend of the threshold was acquired with a small sample size of five for each TID group.The result indicates that the ADC is more sensitive in a compound radiation environment.

Suppressing the hot carrier injection degradation rate in total ionizing dose effect hardened nMOSFETs

Annular gate nMOSFETs are frequently used in spaceborne integrated circuits due to their intrinsic good capability of resisting total ionizing dose （TID） effect. However, their capability of resisting the hot carrier effect （HCE） has also been proven to be very weak. In this paper, the reason why the annular gate nMOSFETs have good TID but bad HCE resistance is discussed in detail, and an improved design to locate the source contacts only along one side of the annular gate is used to weaken the HCE degradation. The good TID and HCE hardened capability of the design are verified by the experiments for I/O and core nMOSFETs in a 0.18 μm bulk CMOS technology. In addition, the shortcoming of this design is also discussed and the TID and the HCE characteristics of the replacers （the annular source nMOSFETs） are also studied to provide a possible alternative for the designers.

Influence of characteristics' measurement sequence on total ionizing dose effect in PDSOI nMOSFET

The influence of characteristics’ measurement sequence on total ionizing dose effect in partially-depleted SOI nMOSFET is comprehensively studied. We find that measuring the front-gate curves has no influence on total ionizing dose effect.However, the back-gate curves’ measurement has a great influence on total ionizing dose effect due to high electric field in the buried oxide during measuring. In this paper, we analyze their mechanisms and we find that there are three kinds of electrons tunneling mechanisms at the bottom corner of the shallow trench isolation and in the buried oxide during the backgate curves’ measurement, which are: Fowler–Nordheim tunneling, trap-assisted tunneling, and charge-assisted tunneling.The tunneling electrons neutralize the radiation-induced positive trapped charges, which weakens the total ionizing dose effect. As the total ionizing dose level increases, the charge-assisted tunneling is enhanced by the radiation-induced positive trapped charges. Hence, the influence of the back-gate curves’ measurement is enhanced as the total ionizing dose level increases. Different irradiation biases are compared with each other. An appropriate measurement sequence and voltage bias are proposed to eliminate the influence of measurement.

Influences of total ionizing dose on single event effect sensitivity in floating gate cells

The influences of total ionizing dose （TID） on the single event effect （SEE） sensitivity of 34-nm and 25-nm NAND flash memories are investigated in this paper. The increase in the cross section of heavy-ion single event upset （SEU） in memories that have ever been exposed to TID is observed, which is attributed to the combination of the threshold voltage shifts induced by 7-rays and heavy ions. Retention errors in floating gate （FG） cells after heavy ion irradiation are observed. Moreover, the cross section of retention error increases if the memory has ever been exposed to TID. This effect is more evident at a low linear energy transfer （LET） value. The underlying mechanism is identified as the combination of the defects induced by 7-rays and heavy ions, which increases the possibility to constitute a multi-trap assisted tunneling （m- TAT） path across the tunnel oxide.

Total ionizing dose effect in an input/output device for flash memory

Input/output devices for flash memory are exposed to gamma ray irradiation. Total ionizing dose has been shown great influence on characteristic degradation of transistors with different sizes. In this paper, we observed a larger increase of off-state leakage in the short channel device than in long one. However, a larger threshold voltage shift is observed for the narrow width device than for the wide one, which is well known as the radiation induced narrow channel effect. The radiation induced charge in the shallow trench isolation oxide influences the electric field of the narrow channel device. Also, the drain bias dependence of the off-state leakage after irradiation is observed, which is called the radiation enhanced drain induced barrier lowing effect. Finally, we found that substrate bias voltage can suppress the off-state leakage, while leading to more obvious hump effect.

Synergistic effect of total ionizing dose on single-event gate rupture in SiC power MOSFETs

The synergistic effect of total ionizing dose(TID) and single event gate rupture(SEGR) in SiC power metal–oxide–semiconductor field effect transistors(MOSFETs) is investigated via simulation. The device is found to be more sensitive to SEGR with TID increasing, especially at higher temperature. The microscopic mechanism is revealed to be the increased trapped charges induced by TID and subsequent enhancement of electric field intensity inside the oxide layer.

Total Ionizing Dose Radiation Effects in the P-Type Polycrystalline Silicon Thin Film Transistors

The total ionizing dose radiation effects in the polycrystalline silicon thin film transistors are studied. Transfer characteristics, high-frequency capacitance-voltage curves and low-frequency noises (LFN) are measured before and after radiation. The experimental results show that threshold voltage and hole-field-effect mobility decrease, while sub-threshold swing and low-frequency noise increase with the increase of the total dose. The contributions of radiation induced interface states and oxide trapped charges to the shift of threshold voltage are also estimated. Furthermore, spatial distributions of oxide trapped charges before and after radiation are extracted based on the LFN measurements.

New Method of Total Ionizing Dose Compact Modeling in Partially Depleted Silicon-on-Insulator MOSFETs

On the basis of a detailed discussion of the development of total ionizing dose （TID） effect model, a new commercial-model-independent TID modeling approach for partially depleted silicon-on-insulator metal-oxide- semiconductor field effect transistors is developed. An exponential approximation is proposed to simplify the trap charge calculation. Irradiation experiments with 60Co gamma rays for IO and core devices are performed to validate the simulation results. An excellent agreement of measurement with the simulation results is observed.

Total ionizing dose induced single transistor latchup in 130-nm PDSOI input/output NMOSFETs

Total ionizing dose induced single transistor latchup effects for 130 nm partially depleted silicon-on-insulator （PDSOI） NMOSFETs with the bodies floating were studied in this work. The latchup phenomenon strongly correlates with the bias configuration during irradiation. It is found that the high body doping concentration can make the devices less sensitive to the single transistor latchup effect, and the onset drain voltage at which latchup occurs can degrade as the total dose level rises. The mechanism of band-to-band tunneling （BBT） has been discussed. Two-dimensional simulations were conducted to evaluate the BBT effect. It is demonstrated that BBT combined with the positive trapped charge in the buried oxide （BOX） contributes a lot to the latchup effect.

Modeling operation amplifier based on VHDL-AMS for TID effect

A model of the operational amplifier based on VHDL-AMS is proposed. According to needs of simulating the total ionizing dose(TID) radiation effect, parameters of operational amplifier are taken into account when the performance is specified. The operational amplifier model used for the TID radiation effect simulation is completed after verifying each modeled parameter. And a parameter for describing the external environment is introduced to make the model combined with TID. Finally, an example is used to illustrate the TID effect on the operational amplifier of MC14573, proving the validity of the model.

Total ionizing radiation-induced read bit-errors in toggle magnetoresistive random-access memory devices

The 1-Mb and 4-Mb commercial toggle magnetoresistive random-access memories（MRAMs） with 0.13 μm and 0.18-μm complementary metal–oxide–semiconductor（CMOS） process respectively and different magnetic tunneling junctions（MTJs） are irradiated with a Cobalt-60 gamma source. The electrical functions of devices during the irradiation and the room temperature annealing behavior are measured. Electrical failures are observed until the dose accumulates to 120-krad（Si） in 4-Mb MRAM while the 1-Mb MRAM keeps normal. Thus, the 0.13-μm process circuit exhibits better radiation tolerance than the 0.18-μm process circuit. However, a small quantity of read bit-errors randomly occurs only in 1-Mb MRAM during the irradiation while their electrical function is normal. It indicates that the store states of MTJ may be influenced by gamma radiation, although the electrical transport and magnetic properties are inherently immune to the radiation. We propose that the magnetic Compton scattering in the interaction of gamma ray with magnetic free layer may be the origin of the read bit-errors. Our results are useful for MRAM toward space application.

存储单元抗TID/SEL电路加固技术面积代价研究

在太空辐射环境中,总剂量辐射(Total Ionizing Dose,TID)效应和单粒子闩锁(Single Event Latch,SEL)效应严重影响存储器的可靠性.由此讨论了存储单元TID效应和SEL效应的原理,探讨了基于电路的加固技术(RHBD),设计了4种新的抗TID/SEL存储单元加固方案,并和现有几种方案进行对比,研究了这些加固方案的面积代价.研究结果表明,抗TID/SEL RHBD方案普遍会使存储单元的版图面积增加87.5%以上.提出了一种加固方案,可以在加固性能和面积代价上得到较好的折衷.

Experimental study on radiation effects in floating gate read-only-memories and static random access memories

Radiation effects of the floating gate read-only-memory （FG ROM） and the static random access memory （SRAM） have been evaluated using the 14 MeV neutron and 31.9MeV proton beams and Co-60 γ-rays. The neutron fluence, when the first error occurs in the FG ROMs, is at least 5 orders of magnitude higher than that in the SRAMs, and the proton fluence, 4 orders of magnitude higher. The total dose threshold for Co-60 γ-ray irradiation is about 104 rad （Si） for both memories. The difference and similarity are attributed to the structure of the memory cells and the mechanism of radiation effects. It is concluded that the FG ROMs are more reliable as semiconductor memories for storing data than the SRAMs, when they are used in the satellites or space crafts exposed to high energy particle radiation.

Synergistic effects of neutron and gamma ray irradiation of a commercial CHMOS microcontroller

This paper presents the experimental results of a combined irradiation environment of neutron and gamma rays on 80C196KC20, which is a 16-bit high performance member of the MCS96 microcontroller family. The electrical and functional tests were made in three irradiation environments： neutron, gamma rays, combined irradiation of neutron and gamma rays. The experimental results show that the neutron irradiation can affect the total ionizing dose behaviour. Compared with the single radiation environment, the microcontroller exhibits considerably more severe degradation in neutron and gamma ray synergistic irradiation. This phenomenon may cause a significant hardness assurance problem.

Impact of substrate bias on radiation-induced edge effects in MOSFETs

This paper investigates the effects of gamma-ray irradiation on the Shallow-Trench Isolation （STI） leakage currents in 180-nm complementary metal oxide semiconductor technology. No hump effect in the subthreshold region is observed after irradiation, which is considered to be due to the thin STI corner oxide thickness. A negative substrate bias could effectively suppress the STI leakage, but it also impairs the device characteristics. The three-dimensional simulation is introduced to understand the impact of substrate bias, Moreover, we propose a simple method for extracting the best substrate bias value, which not only eliminates the STI leakage but also has the least impact on the device characteristics.

集成电路和功率器件抗辐射工艺加固技术研究综述

随着我国空间装备的高速发展,尤其是深空探测器,微电子器件抗辐射性能得到广泛关注。抗辐射工艺加固是实现器件抗辐射性能提升的重要途径之一。本文围绕空间总剂量效应和单粒子效应,对近年来集成电路和功率器件辐射效应机理和工艺加固技术的研究进展进行了介绍和总结,为抗辐射工艺加固技术的发展与应用提供了有益参考。