Changes In Leakage Current Research Articles

Role of oxygen in high temperature hydrogen sulfide detection using MISiC sensors

This paper reports on the sensitivity of a MISiC capacitor sensor with a catalytic top contact to gas mixtures, including hydrogen sulfide, at temperatures in excess of 300 °C. The gas concentration may be extracted from the change in leakage current through the capacitor and exposure to H2S gives a response similar to that observed in hydrogen. This indicates that the decomposition of the H2S on the catalytic contact is forming atomic hydrogen, which forms a dipole layer at the dielectric/SiO2 interface. Exposure to oxygen and H2S simultaneously gives a larger hydrogen-like response, which is contrary to that observed when hydrogen and oxygen are mixed. We suggest that this response is related to the influence of the choice of dielectric used to fabricate the capacitor structure, offering the opportunity to develop array technology for unique identification of gas species in a mixture.

Influence of doping level on electrical properties of ZnO-based composite varistor

ZnO-based varistors with different doping levels of antimony and bismuth are prepared and their electrical properties are measured. It is found that when the doping level of Sb is small，with the amount of Sb2O3 increasing，the leakage current changes little，both nonlinear coefficient αL and breakdown nonlinear coefficient αB decrease but both field strength EL and breakdown field strength EB increase; when the doping level of Sb is high，with more Sb2O3 added，the leakage current increases sharply，αL and αB decrease further，and EL and EB drop down suddenly. With doping level of Bi increasing，the leakage current increases，αL and αB increase，but EL and EB decrease.

POLARIZATION CHANGE OF PZTN FERROELECTRIC THIN FILMS UNDER UNIFORM IN-PLANE TENSILE STRESS

ABSTRACT We applied uniform in-plane tensile stress on PZTN ferroelectric thin films of 130 nm in thickness, using a four-point bending test rig and measured the corresponding changes in polarization and leakage current. An initial polarization hysteresis loop, which is different from the repeatable one after repetitive loadings, was observed. In the range of the tensile stress we applied (up to 150 MPa), the remnant polarization decreased linearly in reference to the repeatable hysteresis at a rate of ∼ 0.002 μC cm -2 MPa -1 which is more than two orders smaller than that of bulk PZT materials.The corresponding coercive voltage increased very little(< 0.02V),but the leakage current at small voltages showed a sudden increase during the loading process, changing from an ohmic behaviour (n = 1) when the stress is < 53 MPa to a sub-linear one (n =0.4)forI ∼Vn when the stress is > 109 MPa.

Thermal degradation of anodic niobia on niobium and oxygen-containing niobium

Thermal treatment of anodized niobium and oxygen-containing niobium has been carried out to elucidate the thermal degradation mechanism of niobium capacitors and to clarify the influence of oxygen dissolved in niobium on thermal degradation. The capacitance and leakage current of the anodized specimens increase with thermal treatment above 423 K in air, although the oxygen content in the substrate has no significant effect up to 523 K. At increased temperatures, the changes in capacitance and leakage current are suppressed with increasing oxygen content. The anodic film formed on the Nb-50 at.% O substrate thickens significantly during thermal treatment at 623 K in air, while only a slight reduction of the thickness is evident for those on the niobium and Nb-20 at.% O substrates. In contrast, vacuum thermal treatment at 623 K causes thinning of the anodic film on niobium, with evidently no change in the film thickness on the Nb-50 at.% O substrate. These are interpreted in terms of oxygen diffusion from the anodic film to the substrate as well as thermal oxide growth.

Improved long-term thermal stability of InGaN∕GaN multiple quantum well light-emitting diodes using TiB2- and Ir-based p-Ohmic contacts

In Ga N ∕ Ga N multiple quantum well light-emitting diodes (MQW-LEDs) were fabricated with either Ni∕Au∕TiB2∕Ti∕Au or Ni∕Au∕Ir∕Au p-Ohmic contacts and annealed at 200 and 350°C for 45days. By comparison with companion devices with conventional Ni∕Au Ohmic contacts fabricated on the same wafer, MQW-LEDs with TiB2- and Ir-based Ohmic metallization schemes showed superior long-term thermal stability as judged by the change in turn-on voltage, leakage current, and output power, a promising result for applications where reliable operation at high temperature is required.

Comparative study of passivation mechanism of oxygen vacancy with fluorine in HfO2 and HfSiO4

It has been experimentally observed that the incorporated fluorine will greatly improve the reliability of high-permittivity gate dielectric based transistors, but the role of fluorine passivation on leakage current change through gate is still a debated issue. The authors performed first-principles calculations to study the role of fluorine in oxygen vacancies in HfO2 and HfSiO4. They found that fluorine behaves completely differently in these two gate dielectrics. Fluorine can passivate the gap states of HfO2 completely but has no effect on the passivation of oxygen vacancies in HfSiO4, which is a possible explanation to the controversy surrounding varying leakage current.

Charge trapping in nitrided HfSiO gate dielectric layers

The effects of HfSiO nitridation on charge trapping and long-term dielectric reliability are investigated. A comparison between decoupled plasma nitridation, annealing in NH3, and no nitridation is made. It was found that thinner HfSiO layers show less trapped charge. Decoupled plasma nitridation resulted always in a larger hysteresis in the characteristics. A common behavior in all samples was seen at elevated temperatures, which corresponds to lower trapped charge and higher leakage current. Dependence between the trapped charge and the leakage current changes with temperature was established.

Asymmetric Distribution of Charge Trap in HfO2-Based High-k Gate Dielectrics

The time-dependences of leakage currents by electrons and holes flowing through HfO2-based high-k gate dielectric films under constant voltage stresses are investigated by a carrier separation method using field-effect transistor structures. The ratio of the electron current to the hole current depended on gate voltage and the type of transistors. In the case of unbalanced charge injection, the trapping of the major leakage current carriers controlled the time dependence of both leakage currents. However, in the case of balanced injection, some of the injected electrons were trapped near the gate, while some of the injected holes were trapped near the substrate, giving rise to the both current reduction. As a result, both leakage currents reduced. Capacitance change during the relaxation after the removal of the gate voltage stress was consistent with the leakage current change. The relationship between the electron-/hole-trapping centers and oxygen-related defects in high-k dielectric films is discussed.

전하량제어에 의한 주기적 분극반전 Ti:LiNbO3(PPLN) 제작 공정에 관한 연구

Ti 확산 리튬나오베이트 채널 광도파로의 z-축 분극을 주기적으로 <TEX>$180^{\circ}$</TEX> 위상 변화시키는 Ti:PPLN 제작 공정을 검토하고, 개선하였다. 분극반전 공정에 적합한 지그와 Labview 프로그램을 이용하여 전하량 제어시스템을 고안하였다. 분극반전에 필요한 전하량으로부터 분극에 적절한 고전압 펄스와 duty-cycle을 조절하였으며, 분극에 필요한 임계 전압 보다 작은 전압을 인가한 상태에서 누설전류의 변화를 관찰하여 절연파괴 현상을 또한 최소화하였다. A fabrication process of periodic electric field assisted poling of Ti-diffused channel waveguides in LiNbO3 (Ti:PPLN) has been developed and improved using a periodic 180o phase inversion along the z-axis. The zig for poling inversion and the Labview program of charge control have been devised. Pulse high voltage and duty cycle were adjusted based on the estimated charge required for poling inversion. Monitoring the change of leakage current under applied voltage less than the coercive voltage also minimized a breakdown.

Carrier separation analysis for clarifying carrier conduction and degradation mechanisms in high-k stack gate dielectrics

The carrier conduction and the degradation mechanism in n +gate p-channel metal-insulator-semiconductor field-effect-transistors with HfAlO X (Hf: 60 at.%, Al: 40 at.%)/SiO 2 dielectric layers have been investigated using carrier separation method. Since gate current depends on substrate bias and both electron and hole currents are independent of temperature over the range of 25–150 °C, the conduction mechanism for both currents is controlled by a tunneling process. As the interfacial SiO 2 layer (IL) thickness increases in a fixed high-k layer thickness ( T high-k), a dominant carrier in the leakage current changes from hole to electron around 2.2-nm-thick IL. This is due to an asymmetric barrier height for electrons and holes at the SiO 2/Si interface. On the contrary, in the case of a fixed IL thickness of 1.3 nm, the hole current is dominant in the leakage current, regardless of T high-k. It is shown that the dominant carrier in the leakage current depends on the structure of the high-k stack. Both electron and hole currents for the stress-induced-leakage-current (SILC) state increase slightly relative to the initial currents, which means that the trap generation in the high-k stack occurs near both the conduction band edge of n +poly-Si gate and the valence band edge of Si substrate. The electron current at soft breakdown (SBD) state dramatically increases over that for the SILC state, while the hole currents for both the SILC state and SBD are almost the same. This indicates that the defect sites generated in the high-k stack after SBD are located at energies near the conduction band edge of n +poly-Si gate. Both the defect generation rate and the defect size in the HfAlO X /SiO 2 stacks are large compared with those in SiO 2. It is inferred that, in high-k dielectric stack, the defect generation mainly occurs in the high-k side rather than the IL side, and the defect size larger than the case of SiO 2 could be related to a larger dielectric constant of the high-k layer.

Effect of the interfacial SiO2 layer thickness on the dominant carrier type in leakage currents through HfAlOx∕SiO2 gate dielectric films

The carrier conduction mechanism of leakage current in n+-gate p-channel metal-insulator-semiconductor field-effect-transistors with HfAlOx (Hf:60at%,Al:40at%)∕SiO2 dielectric layers has been investigated using the carrier separation method. Since the gate current depends on the substrate voltage and both electron and hole currents are independent of temperature in the range of 25–150°C, the conduction mechanism for both currents is a tunneling process. It is shown that the dominant carrier in the leakage current depends on the structure of the high-k stack. When the interfacial SiO2 layer (IL) thickness increases at a fixed high-k thickness (Thigh-k), the dominant carrier in the leakage current changes from hole to electron at ∼2.0–2.3-nm-thick IL, because of asymmetric barrier height for electron and hole in the SiO2∕Si system. In contrast, for the case of a fixed IL thickness of 1.3nm, the hole current dominates in the leakage current, regardless of Thigh-k, due to symmetric barrier height of the conduction and valence bands in the HfAlOx∕Si system.

Isothermal capacitance transient spectroscopy of pseudomorphic high-electron-mobility transistors

The surface electronic properties of AlGaAs/InGaAs pseudomorphic high-electron-mobility transistors were investigated by isothermal capacitance transient spectroscopy (ICTS) and gate-leakage current characteristic measurements. Both hole- and electron-like trap spectra were observed by ICTS measurements on gate–source/drain capacitance. We observed enhancement of leakage current and drastic change of static and transient capacitance behavior around a pinch-off voltage. The leakage characteristics and ICTS results were explained in terms of a surface states model.

A method for detecting the transition from corona from water droplets to dry-band arcing on silicone rubber insulators

The paper presents an investigation on the use of partial discharge (PD) as a means to study the development of leakage current (LC) on silicone rubber insulators in a salt-fog chamber. Simultaneous measurements of LC and PD on dead-end type silicone rubber insulators exposed to different combinations of electrical stress and salt-fog salinity are performed. The results show that for an electrical stress of 33 V/mm applied to the insulator, the average LC experiences gradual changes and reaches a critical level (around 1 mA) where dry-band arcing is observed after 20 minutes at 2300 /spl mu/S/cm, and after 25 minutes at 1800 /spl mu/S/cm. The corresponding PD levels reach hundreds of pC after 15 minutes at 2300 /spl mu/S/cm, and after 20 minutes at 1800 /spl mu/S/cm. For a salinity corresponding to 1800 /spl mu/S/cm and stress of 26 V/mm, the LC changes much more gradually and reaches the critical level only after approximately 60 minutes. The corresponding PD reaches hundreds of pC after 30 minutes and more than 1500 pC after 60 minutes. Pattern recognition techniques have been applied to investigate the transition from corona to dry-band arcing. The features extracted from the maximum and mean apparent charge trends are found to be useful to cluster and classify the two phenomena. Simultaneous visual observations of the discharges on the insulator surface support the results. The investigation, therefore, shows that PD is a sensitive method for detecting the transition from corona from water droplets to dry-band arcing and an alternative method for studying the early aging stage of silicone rubber insulators.

Study of natural diamond detector spectrometric properties under neutron irradiation

Natural diamond detector (NDD) performance was studied up to a neutron fluence of 10 15 neutron/cm 2. The variations of the NDD spectrometric response to incident α-particles from 241Am source after exposure to fast neutron fluences up to 3×10 16 n/cm 2 were examined. No significant variations up to the level of 10 14 n/cm 2 were observed. Degradation of charge collection efficiency at higher fluences is reported. No remarkable increase of the NDD leakage current and count rate change had been observed up to a neutron fluence of 3×10 16 n/cm 2. The charge collection efficiency variations of neutron irradiated diamond spectrometer were studied ex situ under γ-rays, β-radiation and visible light excitation. Charge collection efficiency restoration up to 75% level and the NDD performance stabilization by extrinsic low-intensity visible light (550 nm< λ<800 nm) or intrinsic excitations have been demonstrated.

Effect of plasma enhanced chemical vapor deposition of SiN x on n-GaN Schottky rectifiers

The electrical properties of lateral geometry GaN Schottky rectifiers were measured before and after deposition of SiN x passivation layers by conventional capacitively coupled plasma enhanced chemical vapor deposition. The rectifiers showed changes in reverse breakdown voltages and higher forward leakage currents for all plasma deposition conditions. The change in rectifier performance was found to depend on plasma exposure time, incident ion energy, atomic hydrogen neutral flux and film stress.

Thermal stability of Cu/TiN and Cu/Ti/TiN metallizations on silicon

The thermal stability of Cu/TiN and Cu/Ti/TiN metallizations on Si, before and after annealing at 450–750°C, was investigated. No change in sheet resistance and reverse-bias diode leakage current was observed for both systems after annealing up to 650°C. After annealing at 750°C, sheet resistance of Cu/TiN/〈Si〉 was doubled and formation of Cu 3Si was observed by X-ray diffraction; on the contrary, the sheet resistance of the Cu/Ti/TiN/〈Si〉 sample remains unchanged and no Cu 3Si is detected. By the same annealing, leakage current density of the diodes with Cu/TiN metallization increases by three orders of magnitude, and the value for diodes with Cu/Ti/TiN metallization also increases, but only by two orders of magnitude. The additional Ti layer thus improves the metallurgical and sheet resistance stability but it cannot completely prevent the diode leakage at high temperature.

Atomic Electric Dipole Moment Measurement Using Spin Exchange Pumped Masers of 129Xe and 3He.

We have measured the T-odd permanent electric dipole moment of 129Xe with spin exchange pumped masers and a 3He comagnetometer. The comagnetometer provides a direct measure of several systematic effects that may limit electric dipole moment sensitivity, and we have directly measured the effects of changes in leakage current that result when the applied electric field is changed. Our result, d(129Xe) = 0.7+/-3.3(stat)+/-0.1(syst)x10(-27)e cm, is a fourfold improvement in sensitivity.

Annealing behavior of gate oxide leakage current after quasi-breakdown

Annealing behavior of thin gate oxide after quasi-breakdown (QB) has been investigated. The result implies that the QB leakage current is consisted of two components: the enhanced tunneling due to locally thinned oxide at interface-damaged region and the conduction through a shortening path. The change of leakage current during annealing is a competitive process of changes of these two components - the recovery of interface damage and the expansion of the shortening path in bulk oxide. A unified model is proposed to explain the mechanism of conduction in QB.

Molybdenum Film Technology For Power Metal Oxide Semiconductor Field Effect Transistor Gate Electrode Applications

Molybdenum (Mo) film as a gate electrode for high-frequency power metal oxide semiconductor field effect transistor (MOSFET) has been investigated. The Mo films were deposited by sputtering in Ar ambient. The Mo films properties depend greatly on the substrate temperature. An accurate pattern was realized for Mo film. Stability and reliability of Mo gates for high-frequency power vertical double-diffused metal oxide semiconductor field effect transistors (VDMOSFETs) are as good as those of polysilicon gates. The shift of threshold voltage is below ±35 mV and the change of gate-source leakage current is less than 5 nA under the stress condition of ±5 MV/cm for 100 h at 250°C. Power gain and drain efficiency improvement of Mo gates for VDMOSFETs have been obtained.

Influence of heavy ion irradiation damage on silicon charged particle detector calibration

The full analytical potential of heavy ion backscattering and elastic recoil detection analysis (ERDA) depends critically on establishing a reliable energy calibration. In order to make accurate measurements of thin film samples we have investigated the changes in the energy calibration of a Si p +-n-n + charged particle detector subjected to heavy ion irradiation over 24 h in a time of flight-energy elastic recoil detection analysis (ToF-E ERDA) measurement. In this study a set of similar Al/ZrO 2/Zr samples were analysed sequentially with 60 MeV 127 I 11+ ions. The calibration change for 16O, 27Al and 90–92,95,96Zr were monitored by tagging individual recoils with their energy derived from the ToF. The calibration parameters for a wider range of elements (Li–Ag) were measured before and after the sequential irradiation with O, Al, Zr and I atoms. The results show that the change in the calibration could be characterised by an increase in the energy interval spanned by one channel and a slight decrease in the channel zero energy. The calibration shift for a given projectile atomic number depends linearly on the fluence of heavy particles impinging on the detector and the consequential increase in detector leakage current. This indicates that for similar irradiation conditions, a correction to account for the calibration shift may be simply determined for each sample from the number of heavy recoil counts registered or from the change in leakage current. Furthermore, the silicon charged particle detector calibration depends on recoil atomic number both before, and after, the heavy ion irradiation. The fluence-induced calibration shift for different recoils can be described by a linear dependence on recoil atomic number.