Oxide Trap Research Articles

Substrate effect on radiation-induced charge trapping in buried oxide for partially-depleted SOI NMOSFET

Substrate effect on radiation-induced charge trapping in buried oxide for partially-depleted SOI NMOSFET

Charge trapping analysis in sputtered BixSe1-x based accumulation-mode FETs

Topological materials have attracted a lot of attention in the field of beyond Complementary Metal Oxide Semiconductor (CMOS) devices. Topological Insulators (TI) have been proposed for future high electron mobility field effect transistor (FET) devices that make the physics of operation and especially the oxide-film interface extremely crucial to understand. The effects of the gate voltage on the charge trapping in TI-based FET devices are reported in this work. Sputtered BixSe1-x was chosen as the TI material. The interfacial chemistry was characterized using X-ray photoelectron spectroscopy (XPS), which shows a presence of Mg2+ and oxygen impurities. A unique hysteresis behavior was found for the gate transfer characteristics, with respect to the gate voltage. This was attributed to the charge trapping in the gate oxide and across the SiO2/BixSe1-x interface. We simulated the effects of charge fluctuations on the resistivity of the film. These devices operate under accumulation mode rather inversion mode. Application of positive gate voltage results in accumulation of electrons in the “n-type” BixSe1-x layer resulting in an increase of conductivity. In order to explain the drain current-gate voltage behavior, we used a simple polynomial model to describe the change in the device characteristics due to charge traps. The model was fitted with our experimental results. We further analyzed the gate leakage current, which showed a good match with trap-assisted tunneling (TAT) process that was used to derive trap parameters. The obtained trap parameters show the presence of ultra-deep charge traps contributing to the hysteretic behavior.

Investigation of Negative Bias Temperature Instability Effect in Partially Depleted SOI pMOSFET

The negative bias temperature instability (NBTI) mechanisms for Core and input/output (I/O) devices from a 130 nm partially-depleted silicon on insulator (PDSOI) technology are investigated. The I/O device degrades more than the Core device under the same stress electric field due to the different gate oxide processes in these two types of devices. Both the oxide trap charge and interface trap lead to the transfer characteristics degradations of the device after NBTI. While the near interfacial traps result in the increase of low frequency noise (LFN). The trap densities near the silicon/gate oxide interface introduced by stress are extracted using the LFN method. NBTI-induced gate current increase is observed for Core device, but not for I/O device. It is result from the enhanced tunneling process, which is induced by the increase of electric field in the gate oxide after charge trapping at or near the channel interface. The gate width and length dependences of NBTI are observed. The enhanced NBTI degradation observed in short channel and narrow channel device is result from the enhanced NBTI effect at channel edge regions. The larger hole concentration is a main cause of the more serious NBTI degradation at the channel edge regions, including the nearby region of STI sidewall along the channel width direction and the gate edge region along the channel length direction. This conclusion is also verified by the TCAD simulations.

Effect of pulsed UV laser irradiation on 4H-SiC MOS with thermal gate oxide

The impact of 193 nm ArF pulsed UV laser irradiation on thermally grown SiO2/4H-SiC structures was investigated. The effect of pulsed UV light on the near-interface oxide trap of SiO2/SiC structure is greater than that on the interface and the near-interface SiC substrate. The defects near the interface do not change monotonously with the increase in irradiation power, which indicates that UV irradiation has at least two effects on SiO2/SiC. When the irradiation power is too high, new defects will be introduced into the oxide layer. This article reveals a potential mechanism for high-energy photon irradiation to change device performance in semiconductor plasma technology.

A detailed study on frequency dependent electrical characteristics of MOS capacitors with dysprosium oxide gate dielectrics

Frequency dependent electrical characteristics of Al/Dy2O3/p-Si/Ag MOS capacitors have been systematically investigated incorporating interfacial chemical structures of the capacitors to specify where interface state signals arise from. The results show that capacitance (C) increases with decreasing in the applied voltage frequency due to the response time dependency of the interface states. Conductance (G) curves have a single peak at the relatively high frequencies as expected. Interestingly, the G curves exhibit two distinct peaks at 400 kHz and lower frequencies. These G peaks are associated with acceptor-like interface (Dit,ac) and donor-like interface (Dit,dn) states. Electrochemical analysis has also depicted that non-stoichiometric DySiOx and SiOx bonds are present at the interface between Dy2O3/Si gate stack. Owing to interactions between mobile charge carriers and possible defect sites present at the DySiOx and SiOx, the Dit,ac and Dit,dn signals have been observed at G curves. In addition, the C hysteresis loop widths decrease with decreasing in the voltage frequencies due to opposite polarity and response time dependencies of the Dit,ac and Dit,dn states. The oxide, interface and border trap densities of capacitors exhibit slight frequency variations and their orders are comparable with device used in the state of the art microelectronics technologies. On the other hand, barrier potential varies from 0.97 eV to 1.136 eV depending on the voltage frequencies. Leakage current density was found to be 1.61 × 10−7 Acm−2 at −1 V and Fowler–Nordheim tunneling mechanism dominates the leakage current conduction. Considering to these results, it can be concluded that the Dy2O3 shows promising dielectric and insulating behavior for the application in future microelectronics technology.

Total-Ionizing-Dose Effects and Low-Frequency Noise in 16-nm InGaAs FinFETs With HfO2/Al2O3 Dielectrics

Total-ionizing-dose mechanisms are investigated in 16-nm InGaAs FinFETs with an HfO2/Al2O3 gate-stack. Transistors are irradiated up to 500 krad(SiO2) and annealed at high temperatures. Irradiated devices show negative threshold-voltage Vth shifts, subthreshold stretch-out, and leakage current increases. These result from positive charge trapping in the gate oxide and shallow trench insulators, and increases in the interface and border-trap charge densities. Low-frequency noise measurements at different temperatures indicate a significant increase of noise magnitude in irradiated devices at an activation energy of ~0.4 eV. Density functional theory (DFT) calculations strongly suggest that transistor Vth shifts are due primarily to hole trapping at oxygen vacancies in HfO2, and the increased noise is due primarily to O vacancies in Al2O3. Additional contributions to the noise from defects in the GaAs buffer layer are also likely, primarily at low temperatures.

Aqueous solution-processed AlOx dielectrics and their biased radiation response investigated by an on-site technique

The effect of annealing temperature on the properties of aqueous solution-processed AlOx thin films is reported in this paper. Specifically, the stability of AlOx based Metal Oxide Semiconductor (MOS) capacitor devices under bias-stress (BS) and biased radiation stress (BRS) were assessed by an on-site technique with bias stress time up to 105 s. A 662-keV Cs137 γ-ray radiation source was used, with circa 92 Gy, for biased radiation stress experiments. In order to better understand the origin of degradation mechanisms, the build-up of charge and generation of defects during the BS and BRS were analyzed by calculation of the variation of oxide trap density (ΔNot) in AlOx bulk and interface trap density (ΔNit) at the oxide/semiconductor interface. It is been found that high annealing temperature (>250 °C) can result in the formation of AlOx thin films with reduced impurities, low leakage current, and satisfactory BS as well as BRS stability. The results of ΔNot and ΔNit vs stress time indicate that AlOx bulk oxide traps dominate the shift of flat-band voltage (VFB) under BRS. Furthermore, ΔNot and ΔNit decrease slightly under positive biased radiation stress (PBRS), while the increase in ΔNot and ΔNit concentrations observed under negative biased radiation stress (NBRS), exhibits a mechanism which differs from the traditional two-stage process theory.

Structural, electronic and magnetic properties of bimetallic PdCo nanoparticles with/without metal oxide support and their interactions with nitric oxide (NO): a first principle (ab initio) material modelling study

We have applied ab initio electronic structure method to search minimum energetic structures of the supported and free bimetallic PdCo nanosized particles by using unbiased (surface modified) Birmingham Cluster Genetic Algorithm code, coupling with density functional theory including dispersion correction (Van der Waals). A detailed analysis of structural motifs and segregation effects of free and supported PdCo nanoparticles has been performed by investigating more than one thousand isomers. Alloying and oxide support effects on bimetallic PdCo in term of electronic, magnetic, structural, energetic and stability were also examined comprehensively by calculating pdos, lowden charge analyses, charge density (differences), second finite energies, mixing (formation) energies, dipole moments, ionization energies, electron affinities, chemical reactivity descriptors and HOMO-LUMO gaps. The optimized structures were characterized by vibrational, dipole moment, STM and XRD analyses for a comparison of further experimental studies. Furthermore, nitric oxide (NO) trapping capabilities of the free or supported nanoparticles and clean or strained (1%, 2%, 3%, 4% and 5%) MgO surfaces have been discussed.

Comparison of the Total Dose Responses of Fully Depleted SOI nMOSFETs With Different Geometries for the Worst Case Bias Conditions

Fully depleted (FD) silicon-on-insulator (SOI) nMOSFETs fabricated using 0.2- $\mu \text{m}$ SOI technology with external body contact (EBC) and floating body (FB) structures are irradiated up to 500 krad(Si) using 60Co gamma rays under the transmission gate (TG) and OFF bias conditions, respectively. The threshold voltage shift of the back transistors due to radiation-induced charge trapping in the buried oxide (BOX) is used to characterize the total dose response of irradiated back transistors. The results indicate that, overall, the TG biased EBC transistors with various gate lengths are more sensitive to the total dose radiation than the OFF biased FB counterparts at low dose levels. Furthermore, for the shorter gate transistors with a supply voltage of 1.8 V, a relatively complex correlation exists between the total dose response and the gate length. In particular, the back transistor of the TG biased 0.20- $\mu \text{m}$ 1.8-V EBC transistor reveals smaller threshold voltage shifts than the OFF biased counterpart at approximately 500 krad(Si) because of the saturation of its threshold shift with increased doses, and a similar radiation response is observed for the TG biased 0.35- $\mu \text{m}$ EBC transistor with a supply voltage of 2.5 V. We found that the 2.5-V back transistors exhibited greater radiation hardness than the 1.8-V counterparts with the same bias configuration in most cases.

Electron radiation effects on the structural and electrical properties of MoS2 field effect transistors

The effects of space radiation on the structural and electrical properties of MoS2 field effect transistors (FETs) were investigated. The 1 MeV electronically equivalent International Space Station (ISS) track was used to apply fluence equivalent to the orbital for 10 (1.0 × 1012 cm−2) and 30 years (3.0 × 1012 cm−2) using the AP8 and AE8 models. X-ray photoelectron spectroscopy (XPS), Raman and photoluminescence (PL) spectra were recorded before and after irradiation. Electron irradiation produced strong desulfurization effects in MoS2 FETs. The PL spectra before and after irradiation did not change significantly, while the and A1g Raman modes were red- and blue-shifted, respectively. The XPS results demonstrated a strong desulfurization effect of the electron beam on MoS2. This reduction indicates a much higher amount of irradiation-induced S vacancies compared to Mo vacancies. The electrical characteristics of the device were measured before and after irradiation. The increase in the channel leakage current after irradiation was attributed to the oxide trapping positive charges. MoS2 FETs irradiated by the electron-beam demonstrated a decreased current. This phenomenon can be attributed to the combination of the states at the SiO2/MoS2 interfaces and Coulomb scattering. Our study provides a deeper understanding of the influence of 1 MeV electron-beam irradiation on MoS2-based nano-electronic devices for future space applications.

Emerging Catalyst Control in Cobalt-Catalyzed Oxidative Hydrofunctionalization Reactions

Oxidative functionalization has emerged as an important pathway in Co-catalyzed hydrogen atom transfer (HAT) hydrofunctionalization reactions. Notably, evidence was found for the participation of organometallic intermediates in such radical-polar crossover processes. These findings provide opportunities for catalyst control that was previously absent in HAT catalysis. In this article, we summarize the recent progress towards this direction involving carbon–heteroatom bond-forming intra- and intermolecular reactions, including work from our own group.1 Introduction2 Oxidative Trapping by Solvents and Intramolecular Nucleophiles3 Intermolecular Oxidative Hydrofunctionalization4 Conclusion and Outlook

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.

Comparison of Total-Ionizing-Dose Effects in Bulk and SOI FinFETs at 90 and 295 K

Bulk and silicon-on-insulator (SOI) n-channel FinFETs with fin widths of 15-40 nm and channel lengths of 45 and 1000 nm were irradiated with 1.8 MeV protons at temperatures of 295 and 90 K. Bulk and SOI FinFETs show improved transconductance and steeper subthreshold slopes before irradiation at 90 K than at 295 K. Increased off-state leakage currents are observed for longer channel bulk FinFETs for doses above 300-500 krad (SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) for 295 and 90 K irradiation, and at lower doses for shorter channel devices. Threshold-voltage shifts for irradiation up to 1 Mrad(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) are greater for SOI devices at 90 K than at 295 K due to enhanced charge trapping in the buried oxide (BOX). TCAD simulations provide insight into radiation-induced trapped-charge densities in the SOI devices.

Route-dependent optimal control of the after-treatment system of diesel engines

In this article, the optimal control problem for nitrogen oxide emission reduction is investigated for diesel engines with a lean nitrogen oxide trap. First, a control-oriented model is developed based on conservation laws. Then, the optimal control problem is formulated as a multistage decision problem and solved using a dynamic programming algorithm under dynamical model constraints. A trade-off between fuel economy and nitrogen oxide emission is considered in the cost function of optimization. To demonstrate the obtained optimal control scheme, the parameters of the lean nitrogen oxide trap model are identified with data obtained from a GT-power-based diesel engine simulator. The numerical simulation results for two standard driving cycles and a stochastically generated driving cycle in comparison to a conventional logic-based control scheme are provided using the identified model in the MATLAB/Simulink platform.

Charge trapping and transfer mechanisms of noble metals and metal oxides deposited Ga2O3 toward typical contaminant degradation

Ga2O3 highlights the high energy band structure for redox reaction. However, information on noble metals and metal oxides deposited Ga2O3 for contaminant elimination and the corresponding mechanisms is still lack. Here, metals and metal oxides deposited Ga2O3 (labeled as M-P and MO-C; M = Ag, Pt, and Pd) were synthesized by photocatalytic and chemical deposition methods and confirmed with XRD and XPS. M-P and MO-C were applied in photocatalytic degradation of three typical contaminants: ciprofloxacin, ronidazole and rhodamine B. The ciprofloxacin and ronidazole degradation rates by Ag2O-C and rhodamine B degradation rate by Ag-P were 3.0, 2.7 and 2.4 times as high as those by pure Ga2O3. This research demonstrates that photocatalytic activities of M-P and MO-C are affected by the types and oxidation states of noble metals, as well as the target contaminants. Potentials of M or MO (E(MΦ) or E(MOCB), defined as work function of the metals or conduction band of the metal oxides) is the determining factor for both charge trapping and charge transfer abilities. The highest photocatalytic activity can be obtained when the E(MΦ) or E(MOCB) was kept at the level just beyond the single electron reduction potential of O2, such as Ag-P and Ag2O-C. Finally, the contaminants-specific photocatalytic activities were related to the different functional reactive species. Findings of this study provide important information for the rational design of M and MO deposited photocatalysts.

A smart noise- and RTN-removal method for parameter extraction of CMOS aging compact models

In modern nanometer-scale CMOS technologies, time-zero and time-dependent variability (TDV) effects, the latter coming from aging mechanisms like Bias Temperature Instability (BTI), Hot Carrier Injection (HCI) or Random Telegraph Noise (RTN), have re-emerged as a serious threat affecting the performance of analog and digital integrated circuits. Variability induced by the aging phenomena can lead circuits to a progressive malfunction or failure. In order to understand the effects of the mentioned variability sources, a precise and sound statistical characterization and modeling of these effects should be done. Typically, transistor TDV characterization entails long, and typically prohibitive, testing times, as well as huge amounts of data, which are complex to post-process. In order to face these limitations, this work presents a new method to statistically characterize the emission times and threshold voltage shifts (ΔVth) related to oxide defects in nanometer CMOS transistors during aging tests. At the same time, the aging testing methodology significantly reduces testing times by parallelizing the stress. The method identifies the Vth drops associated to oxide trap emissions during BTI and HCI aging recovery traces while removing RTN and background noise contributions, to avoid artifacts during data analysis.

Study of oxide trapping in SiC MOSFETs by means of TCAD simulations

SILICON CARBIDE (SiC) material has attracted substantial attention during the last few years as a promising candidate for making power devices for high-temperature operation and under harsh environments. In spite of the considerable progress in device performance, reliability may be a limiting factor for the introduction of SiC MOSFETs in commercial power devices. One of the major reliability concerns is the instability of the threshold voltage in MOSFETs and, similarly, of the flat-band voltage in capacitors under normal operation conditions. This instability is attributed to trapping of channel electrons in interface and bulk oxide traps.The main goal of this work is to investigate how the trapped charges at SiO2/SiC interface influence the C/V curve. In particular, by means of 2-D numerical simulations (SILVACO tools), we could isolate the two different contributions from p-type and n-type doped regions of our MOSFET and we considered both donor and acceptor traps contributions. Then, we compared the simulation results with experimental C/V curves. A good agreement between TCAD simulations and experimental measurements was obtained. So, device simulations can provide a better understanding of such defects at SiO2/SiC interface and we give an insight into the influence of traps, produced during device processing or caused by radiation environment, on the output characteristics of the device.

Understanding the recovery of Ruthenium from acidic feeds by oxidative solvent extraction studies

Abstract Ruthenium (106Ru), a notorious fission product in nuclear reprocessing cycle, which gets partitioned at each step needs to be recovered. The recovery of Ru from acidic high level waste (HLW) is of great importance to the nuclear fuel cycle. Quantitative recovery of Ru was achieved from acidic feeds using oxidative trapping mechanism strategy where NaIO4 was used as an oxidant to convert different species of Ru in acidic phase to RuO4 while n-dodecane was used as trapping agent for RuO4. Stripping was attempted using NaOH and NaClO mixture. Attempt was made to optimize various parameters for 103Ru extraction and stripping. 103Ru tracer spiked simulated high level waste was used to understand the 103Ru behaviour in actual waste. The composition of stripping solution (alkaline hypochlorite) was also optimized to have &gt;95% Ru into the aqueous phase in ca. 180 min.

The radiation response of hafnium oxide based metal-oxide-semiconductor capacitors under 60Co gamma ray

Radiation induced oxide and interface trapping characteristics in Al/HfO 2 /Si MOS capacitor under 60Co gamma ray are studied in this article. We discovered positive oxide trapped charge in the HfO 2 /Si system after gamma-irradiation with different total dose. Post-annealing process can reduce the radiation induced trapped charge density in the HfO 2 /Si system, and SiO 2 layer between HfO 2 and Si can greatly reduce the interface trapped charge density. Moreover, we discovered that oxygen vacancy is the dominant radiation induced defect in bulk HfO 2 , and silicon dangling bond and silicon suboxide are main interface defects related to the radiation induced interface trapping.

TaN Versus TiN Metal Gate Input/Output pMOSFETs: A Low-Frequency Noise Perspective

It is shown that replacing a TiN effective work function metal by TaN results in a pronounced reduction of the low-frequency noise power spectral density (PSD) of thick-SiO2 input/output (I/O) DRAM peripheral pMOSFETs. The 1/ $f$ noise is originating from carrier number fluctuations, suggesting that the observed reduction results from a decrease of the oxide trap density in the SiO2. On the other hand, I/O pMOSFETs with a TiN gate deposited by different methods or used as a sacrificial gate in a gate replacement integration scheme yield a similar high 1/ $f$ noise PSD and corresponding oxide trap density.