Breakdown Voltage Measurements Research Articles

Gate-Oxide-Integrity Characteristics of Vacancy-rich Wafer Compared with Crystal-Originated-Pits-free Wafer as a Function of Oxide Thickness

The dielectric breakdown of oxides with various thickness between 5–70 nm on Czochralski (CZ)-grown silicon wafer had been investigated. To observe the effects of crystal-originated-particle (COP), vacancy-rich wafers and COP-free wafers were compared. In breakdown voltage (BV) measurement, breakdown fractions of vacancy-rich wafers were increased with the increase of oxide thickness (tOX) and showed a maximum value at the tOX range of 10–20 nm. On the other hand, COP-free wafers showed few breakdowns over all the range of tOX. Furthermore, time dependent dielectric breakdown (TDDB) of the vacancy-rich wafers showed higher extrinsic breakdowns than that of the COP-free wafers in the tOX below 20 nm. For the intrinsic breakdown, two groups showed the same charge-to-breakdown (QBD) along the strength of injection current over all the range of tOX. Especially, only in case of vacancy-rich wafer, abnormal increase of current, i.e., hump phenomena, was observed in the range of electric field below the Fowler-Nordheim (F-N) tunneling.

大電流パルスグロー放電の特性

Pulsed glow discharge is one of the candidates for the ion source plasma because it can easily generate large volume plasma even for a short time. This paper describes the characteristics of a transient glow discharge with high current using a low impedance circuit. A low inductance capacitor of 1.89μ F was used in this experiment. The voltage between electrodes and consumed energy were obtained by calculation of circuit equations and measurement of discharge current and static breakdown voltage. The gas used is dry air. As the experimental results, the transient glow discharge with high current above one hundred ampere was generated for several microseconds. It was clarified that cathode fall voltage under this experimental condition is approximately 320V which agrees with the value of normal glow discharge. The glow-to-arc transition occurs when the consumed energy in the cathode fall region reaches almost 35mJ in the present experimental conditions.

DC and pulsed measurements of on-state breakdown voltage in GaAs MESFETs and InP-based HEMTs

The BV DS– I D breakdown characteristics of MESFET and HEMT devices measured at constant gate current are correlated with conventional measurements of gate current due to impact-ionization. The influence of thermal effects on breakdown DC measurements is demonstrated. By adopting pulsed measurements, we confirm that on-state breakdown voltage of InP HEMTs decreases by increasing the temperature, while the opposite occurs in GaAs based MESFETs and HEMTs. We show that DC measurements are not suitable for evaluating on-state breakdown of power MESFETs and HEMTs, and we propose pulsed measurements as a viable alternative.

Breakdown characteristics of MOVPE grown Si-doped GaAs Schottky diodes

The breakdown characteristics of Au/n-GaAs Schottky contacts on metal-organic vapor-phase epitaxy grown Si-doped n-GaAs were measured in the doping range of 6×10 15–1.5×10 18 cm −3. These results are compared with the experimentally measured breakdown voltages by several workers and also with the theoretical calculation predicted by Sze and Gibbons [Sze SM, Gibbons G. Appl. Phys. Lett. 1966;8:111]. Good agreement was observed between the measured data and the breakdown voltages by Sze and Gibbons in the high doping concentrations. The maximum depletion layer width is found to be in good agreement with the theoretical analysis by Sze and Gibbons. The breakdown voltage at higher doping concentration will be useful for the design and development of GaAs switching devices and the emitter-base region of bipolar transistors.

High voltage (450 V) GaN Schottky rectifiers

We fabricated high standoff voltage (450 V) Schottky rectifiers on hydride vapor phase epitaxy grown GaN on sapphire substrate. Several Schottky device geometries were investigated, including lateral geometry with rectangular and circular contacts, mesa devices, and Schottky metal field plate overlapping a SiO2 layer. The best devices were characterized by an ON-state voltage of 4.2 V at a current density of 100 A/cm2 and a saturation current density of 10−5 A/cm2 at a reverse bias of 100 V. From the measured breakdown voltage we estimated the critical field for electric breakdown in GaN to be (2.2±0.7)×106 V/cm. This value for the critical field is a lower limit since most of the devices exhibited abrupt and premature breakdown associated with corner and edge effects.

Over recovery in low pressure sparkgaps

The recovery characteristics of the low pressure sparkgaps in the time interval of 300 /spl mu/s to 50 ms by the influence of 1) gap spacings of 2.5 and 10 mm, 2) pulse voltages of 45 kV rising in 2.5 /spl mu/s for positive and negative polarities, and 3) the pressure range of 1.3-34.7 Pa, have been determined for hydrogen, argon, and deuterium gases. A two-pulse system, capable of generating two pulses rising to 45 kV each in 2.5 /spl mu/s and separated by a variable delay of 100 /spl mu/s to 50 ms, has been used to study the recovery characteristics. It has been observed that the breakdown voltage under the second pulse is higher than the breakdown voltage under the first pulse along the left-hand side of Paschen's characteristics [1] and this has been defined as over recovery (>100% recovery) in these studies. The over recovery was found to be up to 120% and is dependent on the gas pressure { 1 kA), and its reversal. This over recovery in low pressure sparkgaps is due to pressure reduction in the gap after the first pulse discharge. This finding seems to have been reported for the first time. The recovery times are independent of gas pressure for negative polarity. It increases with pressure for positive polarity. It increases with increase in molecular weight of the gas in the gap. Shorter gaps recover faster than longer gaps. The experimental setups, principal of over recovery, measurement of breakdown voltages, and currents, results and discussions are presented here.

High Voltage P-N Junction Diodes in Silicon Carbide Using Field Plate Edge Termination

ABSTRACTIn this paper, we report the successful use of field plates as planar edge terminations for P+-N as well as N+-P planar ion implanted junction diodes on 6H- and 4H-SiC. Process splits were done to vary the dielectric material (SiO2 vs. Si3N4), the N-type implant (nitrogen vs. phosphorous), the P-type implant (aluminum vs. boron), and the post-implantation anneal temperature. The nitrogen implanted diodes on 4H-SiC with field plates using SiO2 as the dielectric, exhibited a breakdown voltage of 1100 V, which is the highest ever reported measured breakdown voltage for any planar ion implanted junction diode and is nearly 70% of the ideal breakdown voltage. The reverse leakage current of this diode was less than 1×10−5 A/cm2 even at breakdown. The unterminated nitrogen implanted diodes blocked lower voltages (∼840V). In contrast, the unterminated aluminum implanted diodes exhibited higher breakdown voltages (∼80OV) than the terminated diodes (∼275V). This is attributed to formation of a high resistivity layer at the surface near the edges of the diode by the P-type ion implant, acting as a junction termination extension. Diodes on 4H-SiC showed higher breakdown than those on 6H-SiC. Breakdown voltages were independent of temperature in the range of 25 °C to 150 °C, while the leakage currents increased slowly with temperature, indicating surface dominated components.

A new gate current extraction technique for measurement of on-state breakdown voltage in HEMTs

We present a new simple three-terminal technique for measuring the on-state breakdown voltage in HEMTs. The gate current extraction technique involves grounding the source, and extracting a constant current from the gate. The drain current is then ramped from the off-state to the on-state, and the locus of drain voltage is measured. This locus of drain current versus drain voltage provides a simple, unambiguous definition of the on-state breakdown voltage which is consistent with the accepted definition of off-state breakdown. The technique is relatively safe and repeatable so that temperature dependent measurements of on-state breakdown can be carried out. This helps illuminate the physics of both off-state and on-state breakdown.

Specifications and performance experiences of internally cooled small-scale SMES

SMES has a high potential for application in power utility, because of high plant efficiency, quick response, and power controllability. SMES is composed of a superconducting coil, vapor-cooled leads, and a power conditioning system. The electrical specifications for SMES are discussed on the basis of input and output power depending on size and application. As breakdown voltage in helium gas is low, an internally cooled magnet system is preferable to a pool boiling one. A model coil for a 100 kWh SMES, which is a typical forced cooled magnet system, was developed in Japan and then successfully tested. A glass–polyimide–glass tape insulation system was investigated in view of electrical and mechanical strength prior to fabrication. The breakdown voltage measurement of a sample with an artificial crack showed sufficient strength. The insulation critical fracture strength has a good agreement with the Mohr–Coulomb criterion.

Streamer propagation and breakdown under ac voltage in very large oil gaps

This paper presents a study of prebreakdown and breakdown phenomena under ac voltage in mineral oil in very large gaps (/spl les/80 cm). The investigations presented concern the measurement of breakdown voltages together with the recording of streamers in rod-plane and sphere-plane electrode systems, at different gap sizes. A breakdown mode specific to ac voltage is found, in which 'bursts' composed of streamers initiated at each half cycle appear. This mode leads to the lowest breakdown fields recorded under ac. Values of the average stress required for burst or direct breakdown modes are deduced from the experiments. Positive streamers are responsible for breakdown in large gaps: their propagation is easy and does not depend on the gap geometry and on the presence of particles. On the other hand, the propagation of negative streamers is quenched when not very divergent fields are used.

Positive streamer propagation in large oil gaps: experimental characterization of propagation modes

This paper presents an experimental study of positive streamer propagation in mineral oil, in large point-plane gaps under impulse voltage. A systematic investigation was done concerning the influence of gap distance (/spl les/35 cm), and voltage from streamer inception up to large overvoltages. The measurements presented concern breakdown voltage measurements, time to breakdown, visualization of streamers (streak and still photographs), electrical measurements (transient current, charge), light emission intensity. Streamers are characterized and then classified into different modes (2nd, 3rd and 4th modes) according to their propagation velocities up to more than 100 km/s. According to the applied voltage, transitions between modes are observed, and correlations are established between charge, shape, and streamer velocity. The physical mechanisms as well as practical consequences are then discussed.

Evaluation of plasma charging damage during polysilicon gate etching process in a decoupled plasma source reactor

Charging induced damage of thin gate dielectric during polysilicon gate etching in a high density decoupled plasma source was investigated for 0.16 and 0.24 μm gates on 30 Å nitrided gate oxide. The undoped polysilicon gates were etched with a HBr/He/O2 based process recipe. The optimized process recipe resulted in vertical profiles (89°–90°) with microloading of <1°. No notching of the polysilicon or punch through of the thin gate oxide was observed. Gate leakage and breakdown voltage measurements after gate formation were made on metal-oxide-semiconductor capacitor structures with antenna ratios ranging from 100:1 to 1000:1. These measurements did not exhibit any damage to the thin gate dielectric. In addition, no significant change in the damage characteristics was observed over a wide process window around the optimized recipe, i.e., increased over etch (OE) time, increased source power, or reduced bias power in the OE step. A soft landing scheme was used for the etching of poly gates. This scheme provides vertical profiles without punch through and with minimum damage to the thin gate oxide and the substrate.

Dielectric performance of interfaces in premolded cable joints

Great progress has been made in developing high-quality insulating materials, in maintaining consistent manufacturing processes, and in designing cable joints for easy installation. However, little attention has been given to the interfaces in cable joints. Greases are generally used as a lubricant for installation of premolded cable joints (excluding heat-shrink and cold-shrink splices), and are therefore always found at these interfaces. Analysis of field-aged cable joints has revealed two common problems related to greases: dry and sticky interfaces causing great difficulties in power disconnection, and interfacial discharges (or surface tracking) leading to dielectric breakdown. The focus of this study is on the dielectric performance of interfaces in cable joints. Measurements of breakdown voltage and pressure were carried out at interfaces of both new and field-aged cable joints. The effect of surface conditions was also investigated. Results show that the dielectric performance at interfaces is intimately related to the surface conditions, and a distinct long-term behavior is found for each type of interface in cable joints. The significance of the results and their implications are discussed.

Breakdown mechanism of liquid nitrogen viewed from area and volume effects

We investigated the area and volume effects on the breakdown strength in liquid nitrogen (LN/sub 2/) to discuss the breakdown mechanism in cryogenic liquids for superconducting power apparatus. We measured breakdown voltages in LN/sub 2/ with and without thermal bubbles over a very wide range of the electrode size. Experimental results revealed that the breakdown mechanism changed from an area dominant to volume effective region at larger electrode configurations in LN/sub 2/. Moreover, we discussed the contribution rate of area and volume effects to the breakdown strength in LN/sub 2/. It was suggested that a mutual contribution of area and volume effects appeared in breakdown characteristics in LN/sub 2/ under thermal bubble conditions, as a phenomenon peculiar to cryogenic liquids. Consequently, we pointed out that it is very important to consider both thermal bubbles and electrode surface condition for HV insulation of superconducting power apparatus.

Boron Implantation into GaAs/Ga0.5In0.5P Heterostructures

The electrical effect of implantation of boron ions with energies from 100 keV to 360 keV into GaAs and Ga0.5In0.5P has been studied. The implantation dose varied from 5×1011 cm-2 to 5×1013 cm-2. Resistivities higher than 1×105 Ω cm for both n-type GaAs and n-type GaInP were measured. C–V and breakdown voltage measurements were used to characterize the electrical properties of implanted n GaInP. GaInP appears to be more sensitive to boron implantation than GaAs, and higher resistivities can be obtained with lower boron doses. Boron implantation at 200 keV followed by a 10-min annealing (T=416 ° C) generates a mid-gap trap level at 1.04±0.02 eV below the GaInP conduction band for Q=2×1012 cm-2 and a trap level at 0.92±0.02 eV for Q=5×1012 cm-2. Low-dose boron ion implantation can give rise to a GaInP passivation-like layer.

Breakdown voltage of the surface glow discharge

Breakdown voltage is an important parameter of the surface glow discharge especially from the standpoint of practical applications. The experimental results of the breakdown voltage measurements for this type of discharge together with the results obtained from theoretical analysis are given. The presented model is based on the calculation of the electric field, trajectories of charged particles (which do not follow the flux lines) and finally on the testing of the condition for the self sustained discharge. The obtained theoretical results are in good agreement with the experimental ones.

Plasma-parameter dependence of thin-oxide damage from wafer charging during electron-cyclotron-resonance plasma processing

In this work, the effects of plasma-parameter variations on the charging damage of polysilicon-gate MOS capacitor test structures exposed to O/sub 2/ electron-cyclotron-resonance (ECR) plasmas are investigated. The results show that charging damage is generated when large potential differences exist across the gate-oxide layers of the MOS capacitor test structures and that these potential differences can only occur in the presence of plasma nonuniformities. These results demonstrate the critical need for plasma uniformity during processing, in particular as device dimensions shrink and gate-oxide thicknesses decrease. The plasma parameters were varied by adjusting the neutral gas pressure and by independently biasing a circular grid and a ring electrode located above the wafer. The damage induced in the test wafers during the plasma exposure was characterized with ramp-voltage breakdown measurements. Radial profiles of the floating potential measured with a Langmuir probe were found to vary nonuniformly when the grid electrode was positively biased due to preferential depletion of electrons relative to ions beneath the grid electrode. An equivalent-circuit model of the test wafer and the wafer-stage electrode predicts that the silicon substrate acquires a potential equal to the average of the wafer surface potential. Comparisons of the calculated profiles of the potential difference across the gate-oxide layers of the test structures and whole-wafer maps of the breakdown-voltage measurements show that the majority of the damage occurs where the oxide potential difference is largest and that the damage only occurs in the presence of plasma nonuniformities.

Superconducting current feeder system for the large helical device

A flexible superconducting (SC) busline was developed as a current feeder system for the fusion experimental device, LHD. An aluminum stabilized NbTi/Cu compacted strand cable was developed to satisfy the fully stabilized requirements at a rated current of 31.3 kA. A pair of SC cables was electrically insulated and installed in a cryogenic transfer line. Measured breakdown voltage in the 77 K helium gas is 8.33 kV. Nine sets of SC current feeders with 45-65 m lengths are installed for LHD. The total heat loads into 80 and 4.2 K levels are estimated to be 2.12 and 1.02 kW, respectively. The SC current feeder system is designed to maintain its rated capacities for 30 minutes, whenever the coolants supplied to the current feeder system are accidentally stopped.

Stability of the gas filled surge arresters characteristics under service conditions

The working point of gaseous filled surge arresters (GFSA) is located near the Paschen curve minimum. It has been proven that the working point of GFSA is more stable when it is located in the vicinity of the Paschen minimum, as in these points the curvature radius is largest and that enables the greatest stability of the working point during exploitation. This paper deals with the influence of external factors (temperatures from -200/spl deg/C to 200/spl deg/C, radiation by high speed neutrons and thermal neutrons in controlled dosage) and working conditions on the stability of commercial GFSA characteristics. Under well controlled laboratory conditions measurements of pulse and DC breakdown voltages were performed for several types of commercial surge arresters. During these measurements, the following parameters were varied: temperature, dosage and energy of the previous neutron radiation, and energy and the number of previous breakdown occurrences on a surge arrester. In accordance to these measurements, a software package was developed to enable the determination of analytical expressions for a suitable pulse characteristics. Statistical treatment of obtained results determined the influence of temperature, previous neutron radiation and previous discharges on the stability of GFSA characteristics. Also, by application of the statistical tests (U-test), the level of irreversible changes in GFSA characteristics under experimental conditions was determined. Obtained results are explained theoretically.

A lightly doped deep drain GaAs MESFET structure for linear amplifiers of personal handy-phone systems

An improved GaAs MESFET structure, named a buried p-layer lightly doped deep drain (BP-LD3) structure, is proposed. This structure can be fabricated by the conventional self-aligned gate and selective ion implantation technologies, and the FET characteristics show a high transconductance, a high breakdown voltage, and a low drain-source resistance. The lightly doped deep drain characterizing this structure was introduced on the basis of a two-dimensional numerical analysis including an impact ionization for a buried p-layer lightly doped drain (BP-LDD) structure which has been applied for high-speed digital ICs. The simulated results clarified that a low breakdown voltage of the BP-LDD structure originates from a high rate of carrier generation due to the impact ionization in the lightly doped drain region. The reason is that both electric field and current density become high in the region. In the new BP-LD3 structure, the electron current expands due to the deep formation of lightly doped drain, therefore impact ionization is reduced. This BP-LD3 structure was fabricated and the FET characteristics were compared with those of the conventional BP-LDD structure, and a structure which is now being studied for linear amplifiers of 1.9 GHz personal handy-phone systems. The measured breakdown voltage of 8.1 V, transconductance of 360 mS/mm, and drain-source resistance of 2.5 /spl Omega//mm for the BP-LD3 structure indicate high potentiality for analog applications.