Leakage Current Variation Research Articles

An intelligent fault detection approach for digital integrated circuits through graph neural networks.

To quickly and accurately realize the fault diagnosis of analog circuits, this paper introduces the graph neural network method and proposes a fault diagnosis method for digital integrated circuits. The method filters the signals present in the digital integrated circuit to remove noise signals and redundant signals and analyzes the digital integrated circuit characteristics after the filtering process to obtain the digital integrated circuit leakage current variation. To the problem of the lack of a parametric model for Through-Silicon Via (TSV) defect modeling, the method of TSV defect modeling based on finite element analysis is proposed. The common TSV defects such as voids, open circuits, leakage, and unaligned micro-pads are modeled and analyzed by using industrial-grade FEA tools Q3D and HFSS, and the equivalent circuit model of resistance inductance conductance capacitance (RLGC) for each defect is obtained. Finally, the superior performance of this paper in fault diagnosis accuracy and fault diagnosis efficiency is verified by comparing and analyzing with the traditional graph neural network method and random graph neural network method for active filter circuits.

Discharge development process and flashover performance of snow-accreted insulators under natural environment

The safe and reliable operation of power system in China is significantly affected by snow-covered insulator. At present, many studies on snow-accreted insulator have been undertaken by domestic and foreign scholars in the laboratory. However, whether the laboratory test is equivalent to the field test and whether it can be directly used to guide the external insulation design of transmission line still need to be evaluated. In this regard, AC flashover test of snow-coated insulator was carried out in the laboratory and field in this paper, and then the characteristics of AC discharge path and the variation of leakage current of snow-accreted insulator with time were obtained, and its flashover performance was compared and analysed. The research results show that the amount of snow on the insulator gradually decreases from the stagnation point at the edge of the shed on the windward side to both sides, which is attributed to the uneven distribution of the local collision coefficient of snow crystal particles on the insulator surface. The arc is yellow during the flashover of snow-accreted insulator in the artificial climate chamber. While in the natural environment, the discharge arc appears blue and purple, and the phenomenon of arc levitation and snow layer shedding can be observed. For composite insulator FXBW-35/70 covered with different degrees of snowing in the natural environment, the flashover path develops along the creepage distance in case of the slight snowing, while the path propagates over the dry arc distance under severe snowing condition. Consequently, the flashover voltage decreases by 48.7%. There are many discrepancies between different types of the insulators, such as the creepage distance, dry arc distance and other structural parameters, and the number of air gap after snowing, which affect arc dynamic development properties. Hence, the electrical performance of composite insulator is better than that of glass insulator, and the snowing flashover voltage of the former is 5.56–9.47% higher than that of the latter.

On-chip leakage current variation measurement using external-reference-free current-to-time conversion for densely placed MOSFETs

This paper proposes a time-domain leakage current measurement circuit that uses an external-reference-free current-to-time conversion. Our proposed current-to-time converter (CTC) utilizes a dual inverter-based conversion to provide a stable reference. We share the CTC among the devices under test (DUTs) for accurate characterization of variation. Our CTC, along with a tree-based switch structure, allows us to densely place and route the DUT transistors using a cell-based design flow similar to a digital circuit design. We demonstrate our circuit by measuring subthreshold leakage currents of 256 minimum sized nMOSFETs in a 65 nm bulk low-power CMOS process. We could successfully extract the variations in subthreshold coefficient and subthreshold leakage current at different temperatures. Our circuit is also robust to supply voltage fluctuation making the circuit suitable for accurate characterization of MOSFET parameters for subthreshold operation.

Abruptly-Switching MoS₂-Channel Atomic-Threshold-Switching Field-Effect Transistor With AgTi/HfO₂-Based Threshold Switching Device

A two-dimension (2D) atomic-threshold-switching field-effect transistor (ATS-FET) was implemented, by connecting an AgTi/HfO2-based threshold-switching (TS) device in series to the drain electrode of the 2D baseline-FET with molybdenum disulfide (MoS2) channel material. We optimized/developed the Ag/HfO2-based TS device because its characteristic is associated to the way how to achieve high performance of the 2D ATS-FET. By reducing the effective device area of the Ag/HfO2-based TS device down to $4~\mu \text{m}^{2}$ , low threshold voltage ( $\text{V}_{\mathrm {T}} \sim 0.42$ V), low threshold current (IT, drain current at the threshold voltage, $\sim 3.79 \times 10^{-11}$ A), and low VT variation (~0.09 V) were achieved. This is because the randomly formed filaments and electric field are better controlled with the scaled effective area. Next, the titanium (Ti)-injection barrier layer was inserted between the top electrode and the switching layer, while maintaining the optimized area in the TS device. The inserted Ti-injection barrier layer prevents the migration of Ag ions into the switching layer, enabling the stable TS operation even under the compliance current of $100~\mu \text{A}$ . Additionally, it locally restricts the region where the filaments are created inside the switching layer, resulting in a 17% lower VT variation and stable IT to approximately $\sim 1.5 \times 10^{-11}$ A in 100 cycles. Due to the low off-state leakage current and low variation characteristic of the optimized AgTi/HfO2-based TS device, the 2D ATS-FET (vs. 2D baseline-FET) shows the reduction of off-state leakage current (by $\sim 10^{2}$ in sub-threshold region) and the stable switching characteristic. The proposed 2D ATS-FET shows stably steep switching characteristics, e.g., sub-threshold swing under forward bias (~19 mV/decade) and reverse bias (~26 mV/decade), because of its abruptly switching characteristics of the TS device.

A Novel Fault Leakage Current Detection Method With Protection Deadzone Elimination

Residual current device is an important switch apparatus to ensure the safe and reliable operation of the power distribution system. This article proposes a novel fault leakage current detection method to eliminate the protection deadzone that is typically associated with the classical leakage current detection method. The proposed method takes the leakage current variation in addition to the instantaneous root-mean-square (rms) value of the leakage current as the indicator of leakage fault. Three mathematical models of leakage current variation calculation are illustrated in detail and a multilevel leakage fault protection strategy is proposed. Simulation and experimental results are presented to validate the effectiveness of the proposed leakage current detection method, and a comparative evaluation of the classical and the proposed leakage current detection methods is conducted to verify the superiority of the proposed method.

Prediction of surface leakage current of overhead insulators under environmental and electrical stresses

Leakage current is one of the critical aspects to consider for overhead transmission line insulator’s condition and performance assessment. As the leakage current increase, the size of the dry band also will increase leads to the dry band arcing, deteriorate the insulator performance and contribute to the development of insulator flashover. Based on the literature study, other than the existence of contaminations on the surface of insulator combined with moisture, the variation in leakage current is also affected by the environmental and electrical stresses. Previous researches have shown the effect of environmental and electrical stresses on surface leakage current based on experimental and simulation results. This paper outlines an analytical approach based on dimensional analysis to propose a new mathematical model of leakage current under environmental and electrical stresses. To justify the applicability of the derived dimensional model, the new model has been validated using previous researcher’s experimental results. The validation indicated that the proposed model had shown a good agreement with the previous experimental results. The proposed dimensional equation for this research work can be potentially used as a predictive performance model to evaluate and monitor the leakage current and insulator’s performance

Study on dry band discharge of wet polluted surface with float potential metal by electro-thermal synchronous observation

Severe partial arc occurred near metal bolts on the composite tower under wet pollution conditions, which had a close relationship with the temperature distribution on the surface. Artificial contamination tests on the small-sized composite plate were carried out. Temperature distribution and leakage current variation of the specimen were acquired synchronously. The effects of float potential metal, pollution layer width, metal shape, and moisture on temperature distribution, dry band formation, and discharge phenomenon were studied by a series of comparative experiments. The results show that the float potential metal makes the temperature distribution of the pollution layer more concentrated. The dry band begins to form in the region with the highest temperature. The formation of a dry band on the narrow pollution layer is faster. The temperature of the dry band endpoint is very high and increases with the extension of the dry band. The formation and passing through of dry band blocks leakage current leading to the occurrence of partial arc. Temperature distribution near metals with sharp shapes is more inhomogeneous. In a humid environment, dry band arc can exist stably and develop to float potential metal. Owing to the rewetting of the dry band, dry band formation, and dry band arc will occur repeatedly.

Radiation sustenance of HfO2/β-Ga2O3 metal-oxide-semiconductor capacitors: gamma irradiation study

β-Ga2O3 is an interesting new generation wide bandgap semiconductor for power device applications. The gamma irradiation was performed on the HfO2/β-Ga2O3-based metal-oxide-semiconductor capacitors at 1 kGy and 200 kGy doses. The leakage current density variation at −1 V is 3.47 × 10−7 A cm−2, 5.90 × 10−7 A cm−2 and 4.91 × 10−6 A cm−2 for the pristine, 1 kGy and 200 kGy devices, respectively. In the case of substrate injection, the Schottky emission mechanism appears to be dominant in the 0.65 to 2.0 MV cm−1 electric field range. The barrier heights (Ni/HfO2/β-Ga2O3) 0.95 eV, 0.86 eV and 0.83 eV were extracted from Schottky emission for the pristine, 1 kGy and 200 kGy doses, respectively. However, as the dose increases to 200 kGy, the charge-trapping favors the trap-assisted Poole–Frenkel (PF) tunneling mechanism. In this case, the PF emission mechanism seems to be dominant for the pristine and 1 kGy in the range of 2.0–4.0 MV cm−1, whereas for 200 kGy it is 1.45 to 4.0 MV cm−1 which indicates that the defect assisted PF tunneling is predominant at 200 kGy irradiation dose. There is an increase in the density of oxide traps (Dot) changes from 1.14 × 1012 cm−2 eV−1 to 1.47 × 1012 cm−2 eV−1, and the density of interface traps has increased from 1.95 × 1011 cm−2 eV−1 to 3.80 × 1011 cm−2 eV−1 for the pristine and 200 kGy samples, respectively. The peaks of Photoluminescence show that the three bands of defects centered at 3.0, 2.7 and 2.2 eV. These peaks have possibly arisen from the vacancies of oxygen. At 200 kGy high dose, the defect band emissions were found at 2.9, 2.6 eV and a broad emission at 2.1 eV indicates the increase in the denisty of oxide-trapped charges within the HfO2 layer.

Influence of top metal electrode on electrical properties of pulsed laser deposited lead-free ferroelectric K0.35Na0.65NbO3 thin films

The present work reports the growth of (100) preferred oriented K0.35Na0.65NbO3 (KNN) thin film on Platinized Silicon substrates via pulsed laser deposition (PLD) technique. The structure of KNN thin films was examined by X-ray diffraction (XRD) technique and Raman spectroscopy while their surface morphology was analyzed by Field Emission Scanning Electron Microscope (FESEM). For interrogation of electrical properties, a metal-ferroelectric KNN- metal (MFM) structure was fabricated. Leakage current characteristics and mechanism of KNN thin film were investigated using different metals (noble metals: Pt, Au; and other metals: Pd, Al, Cr) as the top electrode. The variation in leakage current has been co-related to the different occupancy state of d shell of metals. The effect of top metal electrode on the ferroelectric and dielectric property of KNN thin film has also been studied. The MFM capacitor structure exhibited saturated P-E hysteresis loops having a saturation polarization of 43 μC/cm2 and also showed a high dielectric constant of 1090 at 1 kHz.

Studies of radiation effects in Al2O3-based metal-oxide-semiconductor structures induced by Si heavy ions

The radiation effects of metal-oxide-semiconductor (MOS) capacitors based on an Al2O3 gate dielectric were studied using 30 MeV Si heavy ions. To give insights into the types of defects induced by Si ion irradiation in the gate oxide, synergistic experiments involving γ-ray irradiation and Si ion irradiation were carried out. The results revealed that the defects in the as-grown Al2O3 layer were found to be hole trapping centers, whereas Si ion induced new defects were electron trapping centers. The experimental and simulation data of current density-voltage (J-V) curves confirmed that the transmission mechanism of leakage current in the Al2O3 layer was mainly dominated by the Frenkel-Poole mechanism. In detail, the variations of leakage current were mainly due to the attributions of the local built-in electric field-assisted current leakage and the conductive path-assisted current leakage and were found to be dependent on the irradiation condition and Al2O3 thickness. Lastly, the decrease of the gate oxide capacitance of MOS capacitors was attributed to the increase of the series resistance and leakage current in MOS capacitors.

Interpretation of surface degradation on polymeric insulators

Abstract Silicone rubber based polymeric insulators are being used widely used as outdoor insulation for high voltage applications. However, their long-term service life performance is highly dependent on local environmental conditions that cause deterioration of material properties of the insulators. In the present work, tracking and erosion studies are conducted on silicone rubber samples using. Inclined Plane Tracking (IPT) and Erosion method based on IEC 60587. The contaminants used to simulate different environmental conditions are as per standard and in addition acidic rain composition is used. Leakage current flowing through samples was continuously monitored and recorded over the experimental duration. The consequence of leakage current variation is analyzed using. Recurrent Plot (RP) Analysis and this resulted in variation of quantitative parameters Recurrence Rate (RR), Determinism (DET), Entropy (ENT) and Length (L) these are used to interpret the tracking and erosion performance of silicone rubber samples. Further, physico-chemical analysis is conducted using Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDAX) and Fourier Transform Infra-Red (FTIR) spectroscopy to observe surface morphology and chemical changes happened in the samples. Thermo-Gravimetric Analysis (TGA) is performed to observe thermal stability and presence of Aluminum Tri-hydrate (ATH) fillers before and after experiments. The investigations show RP method as a potential tool for detection and diagnostic of polymeric insulators.

Solvent assisted improvement of the dielectric properties and hysteresis behavior in poly‑4‑vinylphenol (PVP) thin films

The role of casting solvent, for casting the PVP dielectric layer in terms of variation in leakage current, dielectric constant and hysteresis voltage was investigated. The leakage current through the pristine (PVP) and cross linked PVP dielectric thin films cast with two different solvents namely Methanol and propylene glycol methyl ether acetate (PGMEA) was measured. Leakage current and dielectric constant in pristine PVP thin films reduced when low polarity solvent was used for casting the films (PGMEA in our case) and further reduced while PVP was cross linked with polymelamine‑co‑formaldehyde (MMF). This variation in the dielectric constant and the leakage current was attributed to the variation of the OH group density present at the polymer dielectric thin films cast with different solvents. The variation of OH group density among the samples was confirmed by the variation of 3290 cm−1 peak intensity, associated with hydroxyl group stretching, in FTIR spectra. Additionally, Contact angle study further revealed that the dielectric thin films cast with different solvents contained different amount of OH group density. Hysteresis voltage, observed in the MIS structure fabricated on these PVP thin films further confirmed variation in OH group densities. These results are critical for development of all organic FETs.

Electrical transport and capacitance characteristics of metal-insulator-metal structures using hexagonal and cubic boron nitride films as dielectrics

Metal-insulator-metal capacitor structures using thick hexagonal and cubic boron nitride (hBN and cBN) films as dielectrics are produced by plasma jet-enhanced chemical vapor deposition, and their electrical transport and capacitance characteristics are studied in a temperature range of 298 to 473 K. The resistivity of the cBN film is of the order of 107 Ω cm at 298 K, which is lower than that of the hBN film by two orders of magnitude, while it becomes the same order as the hBN film above ∼423 K. The dominant current transport mechanism at high fields (≥1 × 104 V cm−1) is described by the Frenkel-Poole emission and thermionic emission models for the hBN and cBN films, respectively. The capacitance of the hBN film remains stable for a change in alternating-current frequency and temperature, while that of the cBN film has variations of at most 18%. The dissipation factor as a measure of energy loss is satisfactorily low (≤5%) for both films. The origin of leakage current and capacitance variation is attributed to a high defect density in the film and a transition interlayer between the substrate and the film, respectively. This suggests that cBN films with higher crystallinity, stoichiometry, and phase purity are potentially applicable for dielectrics like hBN films.

Modeling and Characterization of Inconsistent Behavior of Gate Leakage Current with Threshold Voltage for Nano MOSFETs

A strange relationship of gate leakage current and threshold voltage variation for nano MOSFETs is analyzed using factual strategy and subsequently a physical model is proffered. The gate leakage current increments with the threshold voltage before it diminishes at higher threshold voltage in nanoscale devices. This inconsistent behavior of gate leakage current with threshold voltage variations is precisely clarified in the manuscript through the concept of accord between two contrary operations: threshold voltage roll-off impact and gate leakage current reliance on surface potential. The tunneling gate leakage current density diminishes with threshold voltage over surface potential. However, the threshold voltage roll-off impact causes higher threshold voltage for larger channel length devices. The net gate leakage current is adjusted by these two contrary functions of threshold voltage. In addition, the rate of accretion of the gate leakage current with threshold voltage variation is also analyzed. The impact of the increase in the power supply voltage on the rate of accretion of the gate leakage current vs. threshold voltage curve is also explored. Thorough methodical TCAD simulations are accomplished to validate the proffered models. Both the experimental outcomes, TCAD simulations and physics based models are implemented to uncover and clarify the threshold voltage gate leakage relationship, particularly for nano MOSFETs. The proposed notion is not currently captured in conventional gate leakage nano device models, hence the proffered physical models may be utilized in progression of reliable and trustworthy TCAD simulation tools for nano devices.

Leakage Current Degradation Due to Ion Drift and Diffusion in Tantalum and Niobium Oxide Capacitors

AbstractHigh temperature and high electric field applications in tantalum and niobium capacitors are limited by the mechanism of ion migration and field crystallization in a tantalum or niobium pentoxide insulating layer. The study of leakage current (DCL) variation in time as a result of increasing temperature and electric field might provide information about the physical mechanism of degradation. The experiments were performed on tantalum and niobium oxide capacitors at temperatures of about 125°C and applied voltages ranging up to rated voltages of 35 V and 16 V for tantalum and niobium oxide capacitors, respectively. Homogeneous distribution of oxygen vacancies acting as positive ions within the pentoxide layer was assumed before the experiments. DCL vs. time characteristics at a fixed temperature have several phases. At the beginning of ageing the DCL increases exponentially with time. In this period ions in the insulating layer are being moved in the electric field by drift only. Due to that the concentration of ions near the cathode increases producing a positively charged region near the cathode. The electric field near the cathode increases and the potential barrier between the cathode and insulating layer decreases which results in increasing DCL. However, redistribution of positive ions in the insulator layer leads to creation of a ion concentration gradient which results in a gradual increase of the ion diffusion current in the direction opposite to the ion drift current component. The equilibrium between the two for a given temperature and electric field results in saturation of the leakage current value. DCL vs. time characteristics are described by the exponential stretched law. We found that during the initial part of ageing an exponent n = 1 applies. That corresponds to the ion drift motion only. After long-time application of the electric field at a high temperature the DCL vs. time characteristics are described by the exponential stretched law with an exponent n = 0.5. Here, the equilibrium between the ion drift and diffusion is achieved. The process of leakage current degradation is therefore partially reversible. When the external electric field is lowered, or the samples are shortened, the leakage current for a given voltage decreases with time and the DCL vs. time characteristics are described by the exponential stretched law with an exponent n = 0.5, thus the ion redistribution by diffusion becomes dominant.

Prototyping and performance study of a single crystal diamond detector for operation at high temperatures

Prototype single crystal diamond detectors with different types of metallization and post metallization treatment were fabricated for the applications requiring fast neutron measurements in the Indian Test Blanket Module (TBM) at the International Thermonuclear Experimental Reactor (ITER) Experiment. The detectors were characterized by leakage current measurements to ascertain that the leakage currents are low and breakdown voltages are higher than the voltage required for full charge collection. The detector response to charged particles was evaluated using a 238+239 Pu dual energy alpha source. The detectors showed an energy resolution of about 2% at 5.5MeV. In order to study their suitability for the operation at higher temperatures, leakage current variation and alpha response were studied up to 300°C. At 300°C, peaks corresponding to 5.156MeV and 5.499MeV alphas could be separated and there was no significant degradation of energy resolution. Finally, the detector response to fast neutrons was evaluated using a Deuterium-Tritium (D-T) neutron generator. The observed spectrum showed peaks corresponding to various channels of n-C interactions with a clear isolated peak corresponding to ~8.5MeV alphas. The detectors also showed high sensitivity of 3.4×10−2cps/n/(cm2s)–4.5×10−2cps/n/(cm2s) and excellent linearity of response in terms of count rate at different neutron flux in the observed range of 3.2×105n/(cm2s) to 2.0×106n/(cm2s).

Effect of ultrasound on reverse leakage current of silicon Schottky barrier structure

The influence of ultrasonic loading on reverse current–voltage characteristics of Mo/n–n+–Si structures has been investigated. The research of leakage current variation has been carried out for various ultrasonic wave frequencies (4.1 and 8.4 MHz), intensities (up to 0.8 W/cm2) and loading temperatures (130–330 K). The observed reversible acoustically induced increase in reverse currents was as large as 60%. It has been found that dominant charge transfer mechanisms are the thermionic emission (at high temperature) and the phonon-assisted tunneling (at low temperature). The ultrasound loading affects both processes due to the decrease of Schottky barrier height and binding energy of the electron on the trap.

Tunable dielectric properties of TiO2 thin film based MOS systems for application in microelectronics

Post-deposition annealing (PDA) is an inherent part of a sol-gel fabrication process to achieve the optimum device performance, especially in CMOS applications. Annealing removes the oxygen vacancies and improves the structural order of the dielectric films. The process also reduces the interface related defects and improves the interfacial properties. Here, we applied a sol-gel spin-coating technique to prepare high-k TiO2 films on the p-Si substrate. These films were fired at 400 °C for the duration of 20, 40, 60 and 80 min to know the effects of annealing time on the device characteristics. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of annealed TiO2 films were examined in Al/TiO2/p-Si device configuration at room temperature. The 60 min annealed film gives the optimum performance and contained 69.5% anatase and 39.5% rutile phase with refractive index 2.40 at 550 nm. The C-V and I-V characteristic showed a significant dependence on annealing time such as variation in dielectric constant and leakage current. This allows us to tune the various electrical properties of MOS systems. The accumulation capacitance (Cox), dielectric constant (κ) and the equivalent oxide thickness (EOT) of the film fired for 60 min were found to be 458 pF, 33, and 4.25 nm, respectively with a low leakage current density (3.13 × 10−7 A/cm2) fired for 80 min at −1 V. The current conduction mechanisms at high bias voltage were dominated by trap-charge limited current (TCLC), while at small voltages, space charge limited current (SCLC) was more prominent.

Investigations of Critical Structural Defects in Active Layers of GaN-on-Si for Power Electronic Devices

The influence of structural defects in the active layer of GaN-on-Si substrates on the vertical leakage current was studied. The structural defects were analyzed by analytical scanning electron microscopy by means of cathodoluminescence (CL). The leakage current was determined by vertical I-V measurements.Two possibilities were found, which give potential explanations for the variations of the vertical leakage current: i) Threading dislocations, which may partially form leakage paths, were detected by CL imaging. ii) Variations of the carbon doping, which is used to tune GaN to a semi insulating material were revealed by CL spectroscopy.

Improvement of I-V Characteristics of Schottky Barrier Diode by 4H-SiC Surface Planarization

Leakage current points in 4H-SiC Schottky barrier diodes (SBDs) were found to be in the same location as rough surface morphologies. Rough surfaces after activation annealing at the Schottky interface of diodes were removed by chemical mechanical polishing (CMP) or catalyst-referred etching (CARE). As a result, this study succeeded in reducing the leakage current and barrier height variation of 1.2 kV SBDs by eliminating surface roughness.