Changes In Leakage Current Research Articles

Investigations into the Impact of Deposition or Growth Techniques on the Field Oxide TID Response for 4H-SiC Space Applications

The total ionising dose (TID) reliability of a phosphorous pentoxide (P2O5) treated SiO2 (silicon dioxide) layer is compared for the first time to other industrially relevant oxides formed on 4H-silicon carbide (SiC). Metal-oxide-semiconductor capacitors (MOSCAPs) are characterised before and after irradiation to ascertain changes in flat band voltage shift, leakage current, and dielectric breakdown (BV). Secondary ion mass spectrometry (SIMS) profiling reveals a significant phosphorus concentration near the SiO2/SiC interface, which led to improved TID resistance. The P2O5 treated oxide had the lowest leakage current at high voltage bias due to the high-temperature (1,000°C) anneal, though it had a significantly negative flat band voltage due to the high concentration of deposited phosphorus atoms. The thermal and P2O5 oxides demonstrated a TID resistance, suffering only minor shifts in flat band voltage, while the P2O5 oxide suffered the smallest decrease in its BV and the smallest leakage current rise, post-irradiation.

Study on Deterioration Characteristics of a Composite Crossarm Mandrel in a 10 kV Distribution Network Based on Multi-Factor Aging.

This paper presents a study that conducted 5000 h of multi-factor aging tests on 10 kV composite crossarms, considering the natural environment in coastal areas and actual power line operations. Various aging conditions, such as voltage, rain, temperature, humidity, salt fog, ultraviolet light, and mechanical stress, were applied during the tests. The research initially analyzed the influence of multi-factor aging on the bending and tensile properties of the full-size composite crossarm. Subsequently, a detailed investigation was carried out to assess the impact of aging on the mechanical properties, electrical insulation properties, and microscopic characteristics of the composite crossarm core bar. Results indicated that the tensile strength and bending strength of the full-size composite crossarm mandrel experienced minimal changes after aging, remaining well within operational requirements. However, the silicone rubber outer sheath's hydrophobicity decreased, leading to the appearance of cracks and holes on the surface, which provided pathways for moisture and salt infiltration into the mandrel. As a consequence, the bending strength and shear strength of the mandrel material were reduced by 16.5% and 37.7%, respectively. Moreover, the electrical performance test demonstrated a slight change in the mandrel's leakage current, while the electrical breakdown strength decreased by 22.8%. Microscopic analysis using SEM, three-dimensional CT, and TGA revealed that a small amount of resin matrix decomposed and microcracks appeared on the surface. Additionally, the fiber-matrix interface experienced debonding and cracking, leading to an increased moisture absorption rate of the mandrel material.

Improvement of electrical insulation performance of silicone rubber cables due to exposure to heat and radiation

AbstractThermal treatments, with and without co‐irradiation with gamma rays, were given to safety‐related cables insulated with silicone rubber for nuclear power plants (NPPs). To examine the effects of the above treatments on the insulation properties of the cables, DC voltages were applied to them and the induced changes in leakage current were measured by the current integration method. As a result, it has become clear that the leakage current is the largest in the pristine untreated cable. In addition, almost no leakage current flows in the cables heated at 200°C or 290°C for several hundred hours. The leakage current remains small when the co‐irradiation with gamma rays was given at 100°C or 200°C for relatively long periods exceeding 1000 h. The reason for these results seems to be that the silicone rubber insulation becomes hardened as a result of the thermal or concurrent treatment, and the transport of ionic carriers becomes difficult. The above results indicate experimentally that the degradation is not a matter of great concern for the insulation performance of silicone‐rubber‐insulated safety‐related cables in NPPs.

Study of changes in leakage currents under a contaminated and moistened surface of insulators of the PS-6B, PS-120A, PSD-70E types of overhead power lines

In the process of operation, insulators are exposed to repeated pollution and atmospheric influences. This is due to the removal of pollutants from industrial metallurgical enterprises, chemical plants and their deposition on the surface of insulators near power transmission lines. In normal operation, when the insulators are dirty, but their surface is not wetted, the active component of the total leakage current can be neglected. It is another matter when the surface of the contaminated insulator is intensively moistened by atmospheric influences, for example: rain, fog, dew, respectively, and the value of the active component of the leakage current also increases in proportion to the conductivity of the formed electrolyte, the layer of contamination on the surface of the insulating surface of the insulator. The article discusses the method of measuring leakage currents on the contaminated surface of various types of glass plate insulators in laboratory conditions, with artificial and natural contamination. In the dry state, a leakage current flows through contaminated insulators, which mainly depends on the electrical capacity of the insulator. A method of calculating the active component of the leakage current is proposed, since the active component of the leakage current is the main parameter for determining energy losses due to its dissipation into the environment. The results of the change in the value of the leakage currents in the time characteristics after wetting the surface layer of pollution to the leakage current in the dry state of the insulator surface are given. The observation of drying processes of a contaminated and moistened surface due to the influence of leakage currents is given. The formation of dried zones on the surface of contaminated insulation of plate insulators of overhead power lines under the action of leakage currents was investigated. An analysis of the obtained results was carried out, conclusions were drawn.

Study on the failure rate of high-power thyristors irradiated by artificial neutron irradiation under different DC bias voltages

High-voltage semiconductor devices such as thyristors, due to the high voltage applied, when encountering atmospheric neutrons in the operating state, may appear single event burnout due to charge multiplication in high-altitude areas. The atmospheric neutron radiation in high-altitude areas can cause damage and interference to semiconductor devices, which seriously threatens their safe operation. However, there is little research on the influence of atmospheric neutron irradiation on the operating life of high-voltage DC transmission system thyristors in high-altitude areas. Therefore, in this paper, the neutron beam of the Atmospheric Neutron Irradiation Spectrometer (ANIS) of China Spallation Neutron Source (CSNS) was used to irradiate the high-power thyristors. The failure rates of different applied voltages under 6.74 × 106 n/cm2/s neutron flux irradiation and the leakage current changes during irradiation were obtained. The failure rate applied voltage relationship curve obtained from the artificial neutron irradiation experiment was converted to the corresponding value in Yangbajing area, China. Through the results of the artificial neutron accelerated irradiation experiment, the thyristor failure rate-voltage formula in different areas can be more accurately estimated. In this way, the reasonable working voltage can be determined according to the operating life demand of the thyristor, and determine the thyristor configuration scheme of the design of the converter station. In addition, it is found that the leakage current of thyristor increases with the increase of neutron irradiation time, which may eventually lead to the degradation of thyristor performance and affect its reliability in the DC transmission system.

Impact of Lanthanum-Induced Dipoles on the Tunneling and Dielectric Properties of Gate-Stack

Threshold voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V_{t}}$ </tex-math></inline-formula> ) engineering is critical and challenging in the advanced logic devices. Inducing interface dipoles by the incorporation of dopants into the gate dielectrics is an emerging scheme to modulate the threshold voltage. However, the impact of those dipoles on gate-stack performance is of great concern. In this work, we present the first-principles calculations of dielectric constant and tunneling current of high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> gate-stack with lanthanum (La) dopants. It is found that incorporation of La improves the local dielectric constant as well as the equivalent oxide thickness (EOT), but degrades the gate leakage current. The calculated results are consistent with the reported experimental data. Furthermore, by analyzing the transmission coefficients and band alignment across the gate-stack, a theoretical explanation for the change of gate leakage current is provided.

Highly stable electrical performances of HfO2-based ferroelectric devices under proton irradiation

The proton irradiation effects on TiN/Zr-doped HfO2 (HZO)/TiN ferroelectric capacitors are investigated in this work. Electrical characterization results show that the change of ferroelectric hysteresis loop and leakage current are negligible under proton irradiation up to fluence 1.0 × 1012 ions/cm2. The decrease of permittivity after irradiation is due to the degradation of the effective carrier concentration in Si substrate induced by displacement damage. The results demonstrate that HZO ferroelectric material is immune to radiation and has the application potential to be used in space system.

An energy and leakage current monitoring system for abnormality detection in electrical appliances

Unsafe electrical appliances can be hazardous to humans and can cause electrical fires if not monitored, analyzed, and controlled. The purpose of this study is to monitor the system’s condition, including the electrical properties of the appliances, and to diagnose fault conditions without deploying sensors on individual appliances and analyzing individual sensor data. Using historical data and an acceptable range of normal and leakage currents, we proposed a hybrid model based on multiclass support vector machines (MSVM) integrated with a rule-based classifier (RBC) to determine the changes in leakage currents caused by installed devices at a certain moment. For this, we developed a sensor-based monitoring device with long-range communication to store real-time data in a cloud database. In the modeling process, RBC algorithm is used to diagnose the constructed device fault and overcurrent fault where MSVM is applied for detecting leakage current fault. To conduct an operational field test, the developed device was integrated into some houses. The results demonstrate the effectiveness of the proposed system in terms of electrical safety monitoring and detection. All the collected data were stored in a structured database that could be remotely accessed through the Internet.

Research of cycloaliphatic epoxy resin and silicone rubber composite insulator interface based on four‐electrode system and temperature rise model

AbstractInterface degradation between mandrel and sheath can cause a decrease in insulation performance and mechanical strength of composite insulators. In this study, the interface ageing properties of cycloaliphatic epoxy resin and silicone rubber composite insulator were compared. A water diffusion test was adopted to simulate the composite insulator ageing in a hot and humid environment. A four‐electrode system was built to detect leakage current at different locations (mandrel, sheath and interface), which is an important basis for evaluating insulator performance. The ageing degree of insulator could be quantitatively characterised by leakage current change. It was found that the infiltrated moisture had a great effect on insulation performance. Based on the water absorption test result, the interface performance of two insulators was mainly influenced by their sheath sealing quality. As an auxiliary evaluation method, temperature rise during the test was recorded using an infrared camera. The experiment results showed that interface degradation was the main factor for the insulation performance decrease of silicone rubber composite insulators. However, insulation level reduction of the cycloaliphatic epoxy resin was caused by the wet sheath. In addition, a model for temperature rise of cycloaliphatic epoxy resin insulators was proposed based on good correspondence between sheath material and insulation. The model incorporated multiple processes such as ageing and heating of insulators, and it can predict the early temperature rise well.

TCAD modeling of bulk radiation damage effects in silicon devices with the Perugia radiation damage model

The “Perugia Surface and Bulk” radiation damage model is a Synopsys Sentaurus Technology CAD (TCAD) numerical model which accounts for surface and bulk damage effects induced by radiation on silicon particle detectors. In this work, the significance of the input parameters of the model, such as electron/hole cross sections and acceptor/donor introduction rates is investigated, with respect to the changes in leakage current, full depletion voltage, charge collection efficiency and the current-related damage factor α (an irradiated device’s figure of merit) of a PIN diode. Different types (IV, 1/C2-V) of comparisons are made between simulation outputs and experimental data taken from irradiated PIN diodes. Finally, the possibility of the analytical model’s validation with the examination of the Low-Gain Avalanche Detector (LGAD) case, and its general application for future silicon sensors is discussed.

Effect of Frequency on Total Ionizing Dose Response of Ring Oscillator Circuits at the 7-nm Bulk FinFET Node

Total ionizing dose (TID) effects at the 7-nm bulk FinFET node are characterized under dynamic and static test conditions through changes in ring oscillator (RO) frequencies, leakage currents, and inverter delays. Results from total-dose exposures using the ARACOR X-ray machine showed that static conditions represented the worst case conditions. Higher operating frequencies resulted in increased leakage currents and inverter delays after irradiation. The rate of change for leakage current was inversely proportional to frequency during exposure. The rate of change for inverter delay was directly related to frequency during TID exposure. Overall, degradations in circuit-level parameters (logic gate delays and operating current) were less than 1% for TID exposures of 435 krad(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ).

Y-doped HfO2 deposited by atomic layer deposition using a cocktail precursor for DRAM capacitor dielectric application

A Y-doped HfO 2 thin film deposited using a cocktail precursor for a DRAM capacitor dielectric application was investigated. It has been difficult to adapt HfO 2 , a potential high-dielectric-constant material, deposited by a typical thin-film deposition technique to actual devices owing to its low dielectric constant of approximately 20, resulting from its monoclinic-phase crystal structure. Although several methods have been investigated to increase the dielectric constant by crystal structure transformation to the tetragonal phase, which has a dielectric constant as high as approximately 40, the formation of the monoclinic phase was not successfully suppressed. In this study, the tetragonal-phase formation of HfO 2 thin films was investigated using a cocktail precursor consisting of Y and Hf precursors. The monoclinic formation suppression mechanism in the Y-doped HfO 2 thin film was determined from the physical and chemical analyses results. Moreover, the leakage current change caused by the introduced oxygen vacancy with respect to the Y dopant concentration was investigated. Improved electrical properties of the dielectric constant and leakage current were achieved with Y-doped HfO 2 .

Hybrid Junction Termination Consisting of a Variation Lateral Doping Structure and a Spiral Polysilicon Resistive Field Plate

A hybrid junction termination structure consisting of a variation lateral doping (VLD) region and a spiral polysilicon resistive field plate (PRFP) is proposed in this brief. Surface electric fields of the VLD region are modulated by the PRFP and distribute more uniformly. Compared with the conventional VLD structure with the same size, its measured breakdown voltage increases by 11%. The breakdown voltage still has a positive temperature coefficient. And, the leakage current changes very little from −40 to 150 °C. Besides, it is more immune to the deviation of the VLD dosage. The deviation range of the VLD dosage increase from −20% - +20% to −50% - +60% when the breakdown voltage keeps above 90% of the maximum value. No extra masks or process steps are needed in power devices with a MOS gate structure, because the gate layer can be used to implement the spiral PRFP. At last, the hybrid termination is not detrimental to the switching characteristic of the device.

Investigation on the Physical Properties of Varistors According to Temperature

This study aims to determine the basic physical properties of varistor, which is a protective element in a surge protection device (SPD) used to prevent damage to electric and electronic equipment due to lightning. To do this, we conducted tests of insulation resistance, leakage current, heating characteristics, accelerated aging, impulse current, and operating duty according to temperature. To measure insulation resistance and leakage current, an S1-1568 insulation resistance tester was used. To measure the temperature rise according to a change in the external environment, a convection oven was employed. For the impulse current test, a surge current generator of a direct lightning strike, which was designed and manufactured according to the IEEE and UL standards, was used. We verified that the leakage current increased and the insulation resistance decreased as the voltage and outside temperature were applied to the varistor. This meant that heating and deterioration accelerated due to the leakage current, depending on the place where the SPD was applied. Heat accumulation due to constant heating could cause a change in the physical properties of a varistor and degradation of performance, leading to failure. The impulse current test results of the varistor through the operating duty test showed that changes in insulation resistance and leakage current did not occur significantly with an increase in the number of impulse applications when the less than the maximum surge currents. On the other hand, the maximum surge current was exceeded, the insulation resistance rapidly decreased, which also rapidly increased the leakage current.

Effect of the post-gate annealing on the gate reliability of AlGaN/GaN HEMTs

In this paper, we investigated the effect of post-gate annealing (PGA) on reverse gate leakage and the reverse bias reliability of Al0.23Ga0.77N/GaN high electron mobility transistors (HEMTs). We found that the Poole–Frenkel (PF) emission is dominant in the reverse gate leakage current at the low reverse bias region (V th < V G < 0 V) for the unannealed and annealed HEMTs. The emission barrier height of HEMT is increased from 0.139 to 0.256 eV after the PGA process, which results in a reduction of the reverse leakage current by more than one order. Besides, the reverse step stress was conducted to study the gate reliability of both HEMTs. After the stress, the unannealed HEMT shows a higher reverse leakage current due to the permanent damage of the Schottky gate. In contrast, the annealed HEMT shows a little change in reverse leakage current. This indicates that the PGA can reduce the reverse gate leakage and improve the gate reliability.

Design of leakage current sensing technique based continues NBTI monitoring sensor using only NMOS

As the technology is scaled-down and with a decrease in oxide thickness, the effect of NBTI is a major reliability issue in semiconductor industries. NBTI is an aging phenomenon in which the PMOS transistor degraded over time. Deviation in the threshold voltage of PMOS transistor results from NBTI with stress time which affects various parameter of SRAM memory such as degradation in drain current, RSNM, HSNM and access time. NBTI induced aging effect on 6 T and 8 T SRAM cell have been analyzed in this paper for the stress time of 10 years. The reliability parameters of 6 T SRAM cell obtained from simulation result shows there is 6.53%, 23.86%, 3.36% and 13.42% change in Hold SNM (HSNM), Read SNM (RSNM), Write margin and standby leakage current respectively after 10 years. Similarly in 8 T SRAM cell HSNM, RSNM, Write margin and leakage current changes by 5.81%, 5.01%, 3.11%, and 13.24% respectively. This paper also presents the leakage current sensing technique based NBTI monitoring sensor using NMOS transistors only. The sensitivity of the sensor is 40 µV/nA and the linearity of the sensor is upto the practical leakage current range of SRAM cell. Thus we can conclude that the proposed sensor works fine with greater linearity and sensitivity.

Damage effect of hafnium oxide gate dielectric based metal–oxide–semiconductor structure under gamma-ray irradiation

The radiation response of HfO2 films on a silicon substrate under gamma rays is studied in this article. HfO2 films with the thickness of 12.8 and 4.3 nm are prepared on a p-type silicon substrate by using the atomic layer deposition method, and the HfO2/Si MOS structure is irradiated under gamma rays with the total dose of 1.2/2.5/4 Mrad. The generation, transportation, and trapping characteristics of radiation induced charges are studied by using electronic, physical, and chemical methods. First, radiation induced oxide and interface trapped charge densities are found to be up to 1012 cm−2, and oxygen vacancies in HfO2 and Hf–Si metallic bonds at the HfO2/Si interface are dominant defects in the HfO2/Si system. Second, the leakage current through HfO2 increases with the increase in the radiation total dose and the crystallinity also increases after a large total dose of irradiation. Third, the valence band offset between HfO2 and Si is found to decrease slightly after irradiation. From the results, we can see that HfO2 is radiation resistant from the aspect of charge trapping even under a very large total dose of radiation, but the radiation induced leakage current and crystal structure change in the HfO2 film cannot be ignored. This provides a reference for microelectronic devices working in the space environment.

Ultraviolet light stimulated water desorption effect on emission performance of gated field emitter array

The performance of silicon gated field emission arrays (GFEAs) was characterized before and after ultraviolet (UV) light exposure. Emission and gate leakage currents were measured on 1000 × 1000 tip arrays by sweeping the gate voltage to 40 V DC with a fixed DC collector voltage of 100 V DC. UV light exposure was used to desorb water molecules from the GFEA surfaces. It was found that, before UV exposure, the gate current was 6 mA at 40 V, whereas after 70 min of UV exposure, the gate current decreased to 0.46 mA, indicating a more than ten times reduction in leakage current between the gate and the emitter. Similarly, the observed collector current was 94 μA at 40 V before exposure, and after UV exposure, the collector current increased to 1.33 mA, indicating an improvement of more than 14 times. During the experiments with UV light, residual gas analyzer measurements showed that the partial pressure for water increased by greater than ten times after 60 min of exposure and then decreased by 1 order of magnitude after 100 min of exposure. The emission and leakage current changes remained even after turning off the UV lamps for several tens of minutes; however, upon the exposure to the atmosphere for a few days, those changes reversed. The enhancement could again be observed after additional UV exposure indicating that the adsorbates (mainly water along with others) on the surface affected the leakage between gate and emitter and field emission. Based on analysis of the IV characteristics before and after UV exposure, the work function of the emitter surfaces increases while the portion of the array tips that emits expands resulting in a decrease in the calculated array tip sharpness as duller tips now emit.

Shape Characteristic Analysis of Chaotic Attractors for Leakage Current Signal of Ice-Covered Insulator

The change and development of leakage current (LC) during the flashover process of insulators are closely related to the discharge process. Characteristic quantities of LC play an important role in the identification and prediction of ice-covered flashover development stages. In this paper, the feature extraction method for LC of ice-covered insulator is discussed based on the shape characteristics of chaotic attractor. Firstly, the power spectrum and the largest Lyapunov exponent are used to analyze the LC of ice-covered insulator qualitatively and quantitatively, which confirmed positive chaotic features during the flashover process. On this basis, the LC is reconstructed in phase space. To solve the problem that the attractor in the high-dimensional space cannot be observed in the phase space reconstruction, the principal vector analysis method is used to project the high-dimensional reconstruction vector into the three-dimensional space to reduce the dimension. Finally, the evolution law of chaotic attractor in each stage of LC under different pollution degree is analyzed and discussed. The results show that the LC of ice-covered insulator has obvious characteristics of attractor shape at different stages of pollution, and is sensitive to the degree of pollution and each stage of development. So the shape of the attractor of LC has important application value for the identification of pollution flashover state and prediction of pollution flashover process of ice-covered insulators.

Failure Mechanism of Multilayer Ceramic Capacitors under Transient High Impact

In recent years, penetrating weapons have been used more and more to attack increasingly hard targets; therefore, the impact of such a penetrating process has increased to an extremely high level. As an important component of a fuze, the reliability of the ceramic capacitor in high-impact environments is key for the normal working of the fuze. In this paper, we found that a high-impact causes parameter drift of the multilayer ceramic capacitor (MLCC), which further causes the fuze to misfire. This paper mainly studies the internal mechanism of the MLCC’s parameter drift during high impact. Firstly, transient physical phenomena, such as capacitance fluctuation and the leakage current increase of the ceramic capacitor under a high acceleration impact, were studied experimentally by a Machete hammer, revealing the relationship between the capacitance change, leakage current change, and acceleration under different working conditions. Secondly, a mechanical model of the ceramic capacitor is established to simulate the change in capacitance value, which shows that the main factor of the capacitance change is the deformation-derived change in the facing area between the electrodes. Lastly, an equivalent circuit model is established to simulate the change in the leakage current, which shows that the main factor of the leakage current change is the piezoelectric resistance of the ceramic dielectric.