Total Ionizing Dose Radiation Research Articles

Bias Dependence of Total Ionizing Dose Response in UTBB FD-SOI Transistors

The impact of continuous bias on the ultra-thin body and buried oxide fully-depleted silicon-on-insulator (UTBB FD-SOI) transistors during total ionizing dose (TID) irradiation is investigated by a device with the single transistor or multiple transistors in parallel. Experimental data of the single transistor shows that the TID bias effect is masked by TID response variation caused by process fluctuation between devices. While the device with multiple transistors in parallel still exhibits a similar TID bias effect as the traditional SOI transistor (TG > OFF > Ground > ON), the process fluctuations between devices are well controlled. Focusing on UTBB FD-SOI parallel transistors, by comparing the results of various bias conditions, the impacts of the drain, gate, and back-gate bias on the TID response of transistors are summarized in detail. Particularly, applying both positive and negative back-gate bias to transistors during TID radiation can obviously increase the TID damage of UTBB FD-SOI parallel transistors, which should be considered in the TID mitigation technique through dynamic back-gate bias. Combined with TCAD simulation, the generation process of oxide-trapped charges in buried oxide (BOX) under different biases is discussed. And, bias dependence of TID response is analyzed from three aspects: fraction of holes escaping initial recombination, holes capture cross section, and spatial distribution of oxide trapped charges. Finally, the TID mitigation calibration law of pMOSFETs is investigated by the empirical model of the back-gate radiation bias effect.

High-dose X-ray radiation induced MgO degradation and breakdown in spin transfer torque magnetic tunnel junctions

Magnetic tunnel junction (MTJ) with magnesium oxide (MgO) tunnel barrier is the core element of spin transfer torque-based magnetic random access memory. For the application in the space environment, the total ionizing dose radiation effects on MTJs need to be evaluated. In this work, the MTJs were exposed to X-ray radiation with different doses of up to 10 Mrad(Si). Measurements of current induced magnetization switching (CIMS) behavior of these MTJs were performed before and after radiation. The results show negligible changes in the tunneling magnetoresistance and current switching properties after 8 Mrad(Si) X-ray radiation. However, with a total dose of 9 Mrad(Si), a significant reduction in junction resistance of a fairly large number of MTJs was observed, which showed characteristics of MTJ breakdown. Moreover, in this study, all experimental MTJs became functionally disabled due to MgO breakdown under 10 Mrad(Si) X-ray radiation. The CoFeB/MgO/CoFeB interface microstructure was observed using X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy (HRTEM). Interfacial structural results indicate that the MgO degradation and breakdown behavior caused by X-ray ionizing radiation can give rise to radiation-induced oxygen vacancies across the tunnel barrier oxide layer.

Study of TID radiation effects on the breakdown voltage of buried P-pillar SOI LDMOSFETs with P-top region

This article presents the numerical investigation on the total ionizing dose (TID) radiation induced breakdown voltage shifting behavior of the silicon-on-insulator (SOI) buried P-pillar (BP) lateral double-diffused metal-oxide semiconductor (LDMOS) with a P-top region (TP). We validate the employed simulation models and structure parameters by the experiments of the 200 V rated SOI BP-LDMOS devices. We also discuss the breakdown voltage (BV) analysis of the SOI BPTP-LDMOS under different doping concentrations in the drift region. Because the lateral breakdown voltage can be effectively enhanced by the P-top region under STI layer, the SOI BPTP-LDMOS behaves a wider Nd window for rated 200 V compared with the SOI BP-LDMOS. Finally, we perform the numerical investigation of the TID radiation effect on the BV shift. Using the TID hardening design with the electric field modulation method, the hardened BPTP-LDMOS can achieve a significant improvement in the TID tolerance compared with the hardened SOI BP-LDMOS, from 575 to 775 krad(Si).

Robustly Stable Ferroelectric Polarization States Enable Long-Term Nonvolatile Storage against Radiation in HfO2-Based Ferroelectric Field-Effect Transistors.

The ferroelectric field-effect transistors (FeFETs) with HfO2-based ferroelectric layers in the gate stacks are emerging as one of the most promising candidates for the next-generation nonvolatile memory devices due to their scalability and compatibility with conventional Si technology. Moreover, owing to the high radiation hardness of the HfO2-based ferroelectric thin films, HfO2-based FeFETs have attracted great interest in the fields of radiation-hard (rad-hard) memory. However, the reliability of their memory states under irradiation, which represents the validity of the stored information, has not been investigated. Here, we focus on the impact of the total ionizing dose (TID) on erased and programmed states of HfO2-based FeFETs. The TID radiation (X-ray) characteristics of erased and programmed HfO2-based FeFETs are characterized using an on-site read operation. Both the erased and programmed states show robust stability under irradiation at a dose rate of 90 rad(Si)/s, and even at 230 rad(Si)/s, only the erased state shows a slight variation. The possible factors contributing to memory state degradation are discussed. Through the analysis of the threshold voltage shift and subthreshold swing evolution, as well as studies of ferroelectric polarization stability under radiation, it is revealed that the erased state degradation is caused by oxide-trapped charges rather than interface degradation or polarization switching. The physical mechanism of the difference in radiation-induced oxide-trapped charges buildup in programmed and erased FeFETs is analyzed to explain different TID radiation characteristics between them. Our work suggests that the HfO2-based FeFETs have great potential in radiation environment applications.

Combined Effect of TID Radiation and Electrical Stress on NMOSFETs.

The combined effect of total ionizing dose (TID) and electrical stress is investigated on NMOSFETs. For devices bearing both radiation and electrical stress, the threshold voltage shift is smaller than those only bearing electrical stress, indicating that the combined effect alleviates the degradation of the devices. The H bond is broken during the radiation process, which reduces the participation of H atoms in the later stage of electrical stress, thereby reducing the degradation caused by electrical stress. The positive charges of the oxide layer generated by radiation neutralize part of the tunneling electrons caused by electrical stress, and consume some of the electrons that react with the H bond, resulting in weaker degradation. In addition, the positive charges in shallow trench isolation (STI) generated by radiation create parasitic leakage paths at the interfaces of STI/Si, which increase the leakage current and reduce the positive shift of the threshold voltage. The parasitic effect generated by the positive charges of STI makes the threshold voltage of the narrow-channel device degrade more, and due to the gate edge effect, the threshold voltage of short-channel devices degrades more.

A study on the influence of dose rate on total ionizing dose effect of anti-fuse field programmable gate array—The irradiation damage is attenuated at low dose rate

The TID (total ionizing dose) in-situ experiments of LC1020B, an anti-fuse FPGA (Field Programmable Gate Array) device, were designed and carried out under different dose rates, and the influence of dose rate on the TID effect of FPGA was studied. The experimental results show that: 1) the TID irradiation failure of the FPGA under different dose rates has nothing to do with the input voltage parameter exceeding the standard. 2) with the decrease of cobalt source irradiation dose rate [171, 26.83, and 2.68 mGy(Si)/s], the TID effect failure dose threshold [168, 229, and 334 Gy(Si), respectively] of the FPGA gradually increased, showing obvious attenuation of low dose rate damage. Theoretical analysis suggests that, compared with the space charge limitation effect, the oxide charge annealing effect plays a dominant role, and longer irradiation time is beneficial to the oxide charge annealing. And based on the experimental data, an FPGA TID analytical model with power consumption current as the damage characterization parameter is established, which lays a foundation for scientific evaluation of radiation effect of anti-fuse FPGAs.

Silicon-Germanium Electronics and Photonics for Space Systems

Space has been aptly called the “final frontier” (thank you, Star Trek!). The application needs of the global space and aerospace communities are predictably many and varied, ranging from a diverse set of communications and imaging satellites, to the GPS constellation, to microwave and millimeter-wave (mmW) remote sensing to support weather forecasting and climate science, to exploration of other worlds, which include: the mighty James Webb Space Telescope (probing the origins of the universe), the shadowed polar craters of the Moon (the search for water ice), Mars surface (colonization?), and Europa (the search for extraterrestrial life in the water ocean beneath the 10 km ice cap).While classically, orbital satellites were massive, tough to launch, and extremely expensive (a few $Bs), the current (and rapidly accelerating) trend has swung decidedly towards using relatively low-cost (a few $M) and easy to launch constellations of single or multi-U CubeSats (1U = 10x10x10 cm3) to cost-effectively address the plethora of emerging needs. These days, this has been increasingly supported by commercial space ventures (e.g., SpaceX, BlueOrigin et al., vs. the old gang—NASA and DoD), which are proliferating rapidly.As appealing as space is for visioning fun new science and slick applications, it remains a decidedly unfriendly place to visit. Space is the quintessential “extreme environment,” bathed in intense radiation from both our Sun (high energy electrons and protons trapped by the Earth’s magnetosphere in radiation belts) and the cosmos (GeV energy galactic cosmic rays from supernovae). By way of level setting, a satellite in the most benign Earth orbit, Low Earth Orbit (LEO – 160-1000 km up from the surface), experiences 100,000 rad of ionizing radiation dose over mission life. In comparison, 500 rad will do a person in! That is, we are asking a lot of our electronics in such systems, and given the extreme cost constraints of launch weight, adding a few inches of lead shielding is not the ideal solution! In addition, it is mighty chilly in space (2.73 K = -455°F, the cosmic background), and when the sunlight shines on you, it gets uncomfortably warm, very quickly (e.g., on the surface of the Moon, from -180°C to +120°C from darkness to light, within a few moments). Yep, space is a tough place to do business.As I have long argued [1], SiGe HBT BiCMOS technology provides a unique solution for many of the needs of these emerging space systems, including: 1) extreme levels of performance (multi-hundred GHz) with the SiGe HBT and high integration levels with on-board CMOS, for realizing compelling system functionality/unit volume, at low cost; 2) the rapid improvement of all electronic circuit relevant performance metrics with cooling, with operational capability down into the mK quantum regime (SiGe HBTs love chilly weather!); 3) the ability to operate robustly up to 150-200°C, with modest performance loss; 4) the ability to operate robustly over wide temperature ranges (in principle from mK to 150-200°C); 5) built-in robustness to multi-Mrad total ionizing dose radiation; and 6) built-in heavy ion induced latchup immunity (read: those pesky GeV cosmic rays).Long ago (1990s), the notion of creating a low-cost Si-based electronic + photonic integrated circuit (EPIC) “superchip” was envisioned (Soref), which brought together advanced SiGe HBTs (analog, RF-mmW), CMOS (digital), and Si integrated photonics (with the possible exception of a laser, which could be flipped onto the die worse case). In essence, EPICs are a low-cost, high-yielding, reliable, highly integrated Si platform for putting electrons and light into the same conversation! Clearly this represents a paradigm shift to business as usual. Now, with even more compelling system functionality/unit volume, at low cost. Such an EPIC superchip could in principle satisfy all-comers-of-new-needs. While photonics has long been used in space (think solar cells, imagers), EPICs are new to that space game, but possess great potential for the emergent needs in this new vision of CubeSat/SmallSat driven space systems, including, thing like: LIDAR (spacecraft-to-spacecraft positioning); deep space and within-constellation optical communications (huge data rate improvement); and on-spacecraft high bandwidth data transport (think data center in the sky for instruments that spew out tons of data that need to get back home quickly). This field of EPICs in space is only a few years old, but already much has been learned, and results look very encouraging.In this invited talk, I will highlight the current status and the future trends of using SiGe electronic and photonics in space systems.[1] J.D. Cressler, Proc. IEEE, vol. 93, pp. 1559-1582, 2005. Figure 1

The Effects of Total Ionizing Dose on the SEU Cross-Section of SOI SRAMs

The total ionizing dose (TID) effects on single-event upset (SEU) hardness are investigated for two silicon-on-insulator (SOI) static random access memories (SRAMs) with different layout structures in this paper. The contrary changing trends of TID on SEU sensitivity for 6T and 7T SOI SRAMs are observed in our experiment. After 800 krad(Si) irradiation, the SEU cross-sections of 6T SRAMs increases by 15%, while 7T SRAMs decreases by 60%. Experimental results show that the SEU cross-sections are not only affected by TID irradiation, but also strongly correlate with the layout structure of the memory cells. Theoretical analysis shows that the decrease of SEU cross-section of 7T SRAM is caused by a raised OFF-state equivalent resistance of the delay transistor N5 after TID exposure, which is because the radiation-induced charges are trapped in the shallow trench, and isolation oxide (STI) and buried oxide (BOX) enhance the carrier scattering rate of delay transistor N5.

Total ionization dose radiation tests results of the epoch timing system with sub-picosecond resolution and stability for its applications in space missions.

We report on the concept, design, and tests of a New Picosecond Event Timer (NPET) device and its response to the total ionizing dose. These radiation tests aimed to verify that the existing version of the NPET device may be used in space missions. The device was subjected to radiation of a total dose of 74 Gy provided by a 60Co source. The epoch timing part of the device was not detectably affected by the radiation dose. After the radiation dose, the epoch timing of single measurement resolution is better than 0.9ps with the overall timing stability characterized by Time Deviation being better than 5fs for averaging times of 100s. The completed device tests and results indicate the possibility of using the existing version of the New Pico Event Timing device electronics for a space mission in which the total radiation dose will not exceed 74 Gy value.

Impact of High TID Irradiation on Stability of 65 nm SRAM Cells

Impact of high total ionizing dose (TID) irradiation on stability of 65 nm static random-access memory (SRAM) cells is investigated in this article. The stability of 65 nm SRAM cells is measured not only by the SRAM array but also by the independent cell test structure. The test chip has been subjected to a TID irradiation of 200 Mrad(Si). Experimental results show a reverse data pattern imprinting effect, i.e., irradiated 65 nm SRAM cells are more inclined to the complementary TID data pattern, and the above asymmetry of irradiated 65 nm SRAM cells is due to the bias-dependent shift in threshold of the pull-down nMOSFETs constituting the SRAM cell.

Application of Total Ionizing Dose Radiation Test Standards to SiC MOSFETs

The total ionizing dose (TID) test standards have been developed based on silicon devices to evaluate the TID response of MOS devices for space use. To estimate the applicability of the existing TID test standards to the wide-gap semiconductor silicon carbide (SiC) devices, 1200 V SiC n-channel MOSFETs from three manufacturers were irradiated with Cobalt-60 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> -rays at the high radiation dose rate of 50 rad(Si)/s and the low radiation dose rate of 0.01 rad(Si)/s, respectively. The threshold voltage of devices under test (DUT) shifted toward negative due to the radiation-induced positive oxide trapped charges. Room temperature (RT) anneal of maximum time of 2100 h and high temperature (HT) accelerated anneal of maximum temperature of 105 °C were performed, causing the threshold voltage shift to recover. The synergetic effects of temperature-gate-bias stress and TID on SiC MOSFETs were experimentally studied. In conclusion, the degradation of SiC MOSFETs irradiated at high dose rate is dominated by the positive trapped oxide charges, and the existing TID test standards are applicable to evaluate the SiC MOSFETs radiation hardness level, but the threshold voltages shift due to HT-gate-bias (HTGB) should be evaluated.

Localized Backside Etching Structure of SOI Substrates on Total Ionizing Dose Effect Hardening for RF Applications

In this work, the localized backside etching (LBE) structure is introduced as a strategy for total ionizing dose (TID) irradiation hardening. Immunity to TID-irradiation-induced radio frequency (RF) property degradation is observed for the first time in SOI substrates with the LBE structure. Identical co-planar waveguide transmission lines (CPW TLines), crosstalk characterization structures, and planar spiral inductors are designed and fabricated on different 8-in SOI wafers to characterize the RF properties of substrates. Electrical characterization in the frequency ranges from 100 MHz to 40 GHz reveals that the LBE structure is beneficial to suppressing the parasitic surface conduction (PSC) effect, which will lead to better RF properties of SOI substrate. It is shown that under <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">60</sup> Co <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> -ray irradiation, RF losses are significantly increased in the case of conventional substrates. In contrast, LBE substrates are almost insensitive to TID irradiation due to suppression of PSC. A developed physical model is proposed to characterize the behavior of inductors under PSC and TID effects, and the improvement by LBE structure on RF TID tolerance is separated through model parameter extraction.

Total Ionizing Dose Radiation Effects Hardening Using Back-Gate Bias in Double-SOI Structure

To mitigate the total ionizing dose (TID) radiation impact, a new structure named double-silicon-on-insulator (DSOI) is introduced in this article. This new structure exhibits potential benefits of reducing the radiation-induced degradation effectively and independently, thanks to the additional electrode, which can be used to control the internal electrical field of the device. With this structure, the TID response and TID mitigation strategy using back-bias are discussed in DSOI nMOSFETs. Then, a 3-D TCAD simulation model is proposed to analyze the radiation-induced leakage path for each bias configuration. The impact of negative back-bias during irradiation on trapped charge distribution is given for both buried oxide layer and shallow trench isolation. At last, a 4k-bit static random access memory is used to verify the effectiveness of back-bias on TID-induced leakage current suppression at the circuit level. The experimental results show the possibility of using back-bias against TID threat.

A Novel S-Gate-Assisted SOI n-MOSFET for Total Ionizing Dose Radiation Reinforcement

In this article, a novel S-gate-assisted silicon-on-insulator n-channel metal–oxide–semiconductor field-effect transistor (SGA SOI n-MOSFET) structure is proposed in order to suppress the total ionizing dose (TID) effect. The new structure settles the radiation-induced leakage current by isolating both the source and drain from the shallow trench isolation (STI) oxides and introducing two auxiliary gates. This work simulates the TID irradiation of three SOI n-MOSFET devices by Sentaurus TCAD and verifies the anti-TID irradiation characteristics of the proposed SGA SOI n-MOSFET. After the novel SGA SOI n-MOSFET was irradiated with 500 krad(Si), the OFF-state leakage current is only marginally increased, the ON-state leakage current is almost unchanged, the threshold voltage drift is 9.423%, and the transconductance degradation is only 7.453%. The simulation results demonstrated the proposed SGA SOI n-MOSFET resisted TID radiation doses up to 500 krad(Si). Meanwhile, the SGA SOI n-MOSFET is much more compact and saves tremendous cost compared with the H-gate-assisted (HGA) SOI n-MOSFET during very large scale integration (VLSI) fabrication and mass production. Moreover, the SGA SOI n-MOSFET solves the disadvantages of the ring-gate-assisted (RGA) SOI n-MOSFET complex aspect ratio <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${W}/{L}$ </tex-math></inline-formula> design. The SGA SOI n-MOSFET offers a better alternative for nonultrahigh radiation dose environments.

Effects of total ionizing dose on transient ionizing radiation upset sensitivity of 40–180 nm SRAMs

Effects of total ionizing dose (TID) on the transient radiation upset sensitivity of commercial static random access memories (SRAMs) were investigated. Commercial SRAMs of three technology nodes were irradiated with Co-60 gamma rays for total dose effects and with pulsed x rays generated using a “Chen-Guang” accelerator for doserate effects. It is shown that TID irradiation and the memory pattern written to the memory array during TID irradiation can substantially affect the transient radiation upset sensitivity of all the SRAMs. First, the memory pattern written to the memory array during TID irradiation is more sensitive to pulsed x rays for all SRAMs. Second, the variation in transient radiation upset sensitivity with total dose has different tendencies for different SRAMs, but the static power current increased with the increase in total dose for all SRAMs. The increase in static power current with total dose and the increasing sensitivity of the memory pattern during TID irradiation are caused by the increasing TID induced leakage current, which results in an asymmetric noise margin of individual memory cells.

Three-dimensional simulation of total ionizing dose effect on SiGe heterojunction bipolor transistor

The damage mechanism of the total ionizing dose (TID) effect of SiGe heterojunction bipolor transistar (SiGe HBT) is explored by using three-dimensional simulation of semiconductor device (TCAD).In the simulation, the trapped charge defects are introduced into different locations of oxidationin SiGe HBT to simulate the TID effect. Then the degradation characteristics of the forward Gummel characteristic and the reverse Gummel characteristic of the device are analyzed, and the TID damage law of SiGe HBT is obtained. Finally, the simulation results are compared with the &lt;sup&gt;60&lt;/sup&gt;Co γ irradiation test results, showing that the trapped charges introduced by TID irradiation in SiGe HBT device mainly affect the Si/SiO&lt;sub&gt;2&lt;/sub&gt; interface near the p-n junction, resulting in the change in the depletion region of the p-n junction and the increase of carrier recombination. Eventually, the base current increases and the gain decreases. The trapped charges generated in the EB spacer oxide layer mainly affect the forward Gummel characteristics, and the trapped charges in the LOCOS isolation oxide layer are the main factor causing the reverse Gummel characteristics to degrade. The experimental results on &lt;sup&gt;60&lt;/sup&gt;Co γ irradiation under different biases are consistent with those from the total dose effect damage law of SiGe HBT obtained by numerical simulation analysis.

Total Ionizing Dose Effects of the Color Complementary Metal Oxide Semiconductor (CMOS) Image Sensor at Different Bias

The experiments of total ionizing dose radiation effects on color CMOS image sensors at different biases were presented. Two bias conditions operated during 60Co γ irradiation, biased and unbiased. In the data processing, the data of four channels were extracted according to the sequence of Bayer array respectively to study the difference between each channel. The full well capacity and dark signal non-uniformity versus the cumulative doses were investigated. After γ-ray irradiation, the full well capacity of the samples decreased along with dark signal non-uniformity increased. Meanwhile, the descending amplitude of full well capacity was different in each channel, but the variation of dark signal non-uniformity was almost consistent. Moreover, the degradations of full well capacity and dark signal non-uniformity were more seriously under-biased.

1/f Noise responses of Ultra-Thin Body and Buried oxide FD-SOI PMOSFETs under total ionizing dose irradiation

This paper investigates the low frequency noise degradation of commercial Ultra-Thin Body and Buried oxide Fully Depleted Silicon on Insulator (UTBB FD-SOI) PMOSFETs are under Total Ionizing Dose (TID) irradiation. According to the experimental results, the 1/f noise of the conduction channel in studied transistors increases differently after irradiation. Based on the carrier number fluctuation (CNF) model with additional carrier mobility fluctuations (CMF), we expand the process of 1/f noise changes at the front and back gates in UTBB FD-SOI devices during TID irradiation. Moreover, the relationship between channel Width/Length ratio (W/L) and the 1/f noise normalized power spectral density at the front gate before and after TID irradiation is also discussed. The trend reducing W/L condition can alleviate 1/f noise degradation in transistors is consistent with the expended theory, which can be a practical reference to develop the UTBB FD-SOI radiation-hardening technology.

Radiation Effects and Mechanisms on Switching Characteristics of Silicon Carbide Power MOSFETs

This paper presents an experimental study of the dynamic and static characteristics of SiC Power MOSFETs in a total ionizing dose radiation environment. Their relationship has also been studied. Furthermore, the factors and mechanisms that affect the switching characteristics of SiC Power MOSFET in a total dose radiation environment are discussed. The change of switching characteristics of SiC VDMOS induced by radiation depends not only on the trapped charge accumulated at the interface and gate oxide above the channel but is also strongly dependent on the parasitic capacitance of the device. The former causes the negative shift of the threshold voltage to decrease the turn-on time and increase the turn-off time, while the latter increases both the turn-on time and turn-off time. The results of the study show that the static and dynamic performance of SiC power MOSFET must be considered simultaneously in the total dose radiation damage assessment and radiation hardening. Namely, the static characteristic represented by the threshold voltage and the dynamic characteristic represented by the turn-off time.

Impact of switching frequencies on the TID response of SiC power MOSFETs

Different switching frequencies are required when SiC metal–oxide–semiconductor field-effect transistors (MOSFETs) are switching in a space environment. In this study, the total ionizing dose (TID) responses of SiC power MOSFETs are investigated under different switching frequencies from 1 kHz to 10 MHz. A significant shift was observed in the threshold voltage as the frequency increased, which resulted in premature failure of the drain–source breakdown voltage and drain–source leakage current. The degradation is attributed to the high activation and low recovery rates of traps at high frequencies. The results of this study suggest that a targeted TID irradiation test evaluation method can be developed according to the actual switching frequency of SiC power MOSFETs.