Showing papers on "Breakdown voltage published in 1998"

Trench-gated MOSFET with bidirectional voltage clamping

Abstract: The gate of a MOSFET is located in a lattice of trenches which define a plurality of cells. Most of the cells contain a MOSFET, but a selected number of the cells at predetermined locations in the lattice contain either a PN diode or a Schottky diode. The PN and Schottky diodes are connected in parallel with the channels in the MOSFET cells, with their anodes tied to the anode of the parasitic diodes in the MOSFET cells and their cathodes tied to the cathode of the parasitic diodes. When the MOSFET is biased in the normal direction (with the parasitic diode reverse-biased), the PN diodes provide a predictable breakdown voltage for the device and ensure that avalanche breakdown occurs at a location away from the trench gate where the hot carriers generated by the breakdown cannot damage the oxide layer which lines the walls of the trench. When the device is biased in the opposite direction, the Schottky diodes conduct and thereby limit charge storage at the PN junctions in the diode and MOSFET cells. This reduces the power loss in the MOSFET and improves the reverse recovery characteristics of the device when its bias is switched back to the normal direction.

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

Abstract: 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.

AC (60 Hz) and impulse breakdown strength of a colloidal fluid based on transformer oil and magnetite nanoparticles

Abstract: A new class of colloidal dielectric fluids was developed by modifying the mineral oil based ferrofluids to enhance their dielectric performance. At its optimum composition, the colloidal insulation has AC (60 Hz) breakdown strength close to that of the carrier oil, while its impulse voltage withstand in needle to sphere geometry is improved: for the needle positive, the impulse breakdown voltage increased up to 50% as compared to the dry and degassed mineral oil (Exxon Univolt 60) while for the needle negative the breakdown value remains close to that of the oil carrier, so that the two values are practically equal. The PD inception voltage (AC, 60 Hz, 500 V/sec rise, needle to sphere geometry) showed and increase of up to 30%. The new colloidal insulation showed little change in electrical resistivity and kinematic viscosity after accelerated aging at 185/spl deg/C.

High voltage mosfet structure

Abstract: A high voltage MOSFET with low on-resistance and a method of lowering the on-resistance for a specific device breakdown voltage of a high voltage MOSFET. The MOSFET includes a blocking layer of a first conductivity type having vertical sections of a second conductivity type or the blocking layer may include alternating vertical sections of a first and second conductivity type.

Trench MOSFET having improved breakdown and on-resistance characteristics

Abstract: A trench MOSFET is formed in a structure which includes a P-type epitaxial layer overlying an N+ substrate. An N drain region is implanted through the bottom of the trench into the P-epitaxial layer, and after a diffusion step extends between the N+ substrate and the bottom of the trench. The junction between the N drain region and the P-epitaxial layer extends between the N+ substrate and a sidewall of the trench. In some embodiments the epitaxial layer can have a stepped doping concentration or a threshold voltage adjust implant can be added. Alternatively, the drain region can be omitted, and the trench can extend all the way through the P-epitaxial layer into the N+ substrate. A MOSFET constructed in accordance with this invention can have a reduced threshold voltage and on-resistance and an increased punchthrough breakdown voltage.

Propagation of positive and negative streamers in oil with and without pressboard interfaces

Abstract: Inception and propagation of streamers in a point-plane gap, with and without pressboard interface parallel to the field, have been studied. Current and light emission have been recorded. Positive streamers propagate at /spl sim/2 to 4 mm//spl mu/s at voltages to 2/spl times/ the minimum breakdown voltage. Above this voltage, a fast event (>100 mm//spl mu/s) may occur, preceded by streamers propagating with velocities in the 10 to 20 mm//spl mu/s range. The negative streamers have /spl sim/2/spl times/ the breakdown voltage as the positive ones. Even negative streamers may develop into a slower kind of fast event. Solid pressboard parallel to the field does not change the breakdown voltage, but makes inception of fast events easier. The breakdown process in oil shows several similarities to a gas breakdown.

Adaptive power supply for avalanche photodiode

Abstract: An adaptive power supply for an avalanche photodiode (APD) is used to determine an optimum bias voltage. Without an optical signal input the adaptive power supply applies a swept voltage to the APD while monitoring the photodiode current. When breakdown occurs, the voltage is noted and the bias voltage from the adaptive power supply is set at a specified offset below the breakdown voltage. Where a source of optical digital data signal is present, it is coupled to the input of the APD via a programmable optical attenuator. The electrical digital signal output from the APD is input to a bit error rate counter, the output of which is monitored. For different optical power levels the APD bias voltage is swept by the adaptive power supply, determining a constant power level curve over which the bit error rate is virtually zero. This is repeated for a plurality of optical power levels, the resulting family of curves defining a region within the bit error rate is virtually zero. The adaptive power supply is set to a value that falls within the virtually zero bit error rate region for the expected optical power level input.

Method for making a silicon-on-insulator MOS transistor using a selective SiGe epitaxy

Abstract: Disclosed is a method for manufacturing a metal-oxide-semiconductor (MOS) device formed in an epitaxial silicon layer on insulator substrate comprising the steps of forming a field oxide layer defined an active region of the MOS device in the silicon layer and forming a gate oxide on the silicon layer; forming a gate electrode on the gate oxide, and self-aligned implanting a dopant of low concentration to form a lightly doped drain region; forming an oxide spacer in both sides of the gate electrode; growing a SiGe epitaxial layer having a lower bandgap than the silicon layer on the portion of the exposed silicon layer; and implanting a dopant of high concentration over the SiGe epitaxial layer to form a highly doped source/drain region. This invention can easily manufacture an SOI MOS device having a low source/drain series resistance and a high breakdown voltage without additional complex processes.

MOSgated trench type power semiconductor with silicon carbide substrate and increased gate breakdown voltage and reduced on-resistance

Abstract: A MOSgated trench type power semiconductor device is formed in 4H silicon carbide with the low resistivity direction of the silicon carbide being the direction of current flow in the device drift region. A P type diffusion at the bottom of the U shaped grooves in N− silicon carbide helps prevent breakdown of the gate oxide at the trench bottom edges. The gate oxide may be shaped to increase its thickness at the bottom edges and has a trapezoidal or spherical curvature. The devices may be implemented as depletion mode devices.

Temperature dependence of impact ionization in algan-gan heterostructure field effect transistors

Abstract: We report on the studies of the impact ionization in AlGaN–GaN heterostructure field effect transistors in the temperature range 17–43 °C. The results show that the breakdown voltage and the characteristic electrical field Ei of the impact ionization have a positive temperature coefficient. The value of Ei at room temperature is estimated to be approximately 2.6 MV/cm, which agrees with recent theoretical prediction [J. Kolnik et al., J. Appl. Phys. 82, 726 (1997)].

InAlAs/InGaAs metamorphic HEMT with high current density and high breakdown voltage

Abstract: An In/sub 0.3/Al/sub 0.7/As/In/sub 0.3/Ga/sub 0.7/As metamorphic power high electron mobility transistor (HEMT) grown on GaAs has been developed. This structure with 30% indium content presents several advantages over P-HEMT on GaAs and LM-HEMT on InP. A 0.15-/spl mu/m gate length device with a single /spl delta/ doping exhibits a state-of-the-art current gain cut-off frequency F/sub t/ value of 125 GHz at V/sub ds/=1.5 V, an extrinsic transconductance of 650 mS/mm and a current density of 750 mA/mm associated to a high breakdown voltage of -13 V, power measurements performed at 60 GHz demonstrate a maximum output power of 240 mW/mm with 6.4-dB power gain and a power added efficiency (PAE) of 25%. These are the first power results ever reported for any metamorphic HEMT.

Novel high power AlGaAs/GaAs HFET with a field-modulating plate operated at 35 V drain voltage

Abstract: This paper reports novel high power AlGaAs/GaAs heterostructure FET with a field-modulating plate (FP-HFET), which accomplished dramatic increase of the gate-drain breakdown voltage with greatly suppressed drain-current pulse-dispersion characteristics. The fabricated FETs exhibited excellent power performance up to 35 V at L-band, delivering the maximum power density of 1.7 W/mm.

Breakdown degradation associated with elementary screw dislocations in 4H-SiC p+n junction rectifiers

Abstract: It is well-known that SiC wafer quality deficiencies are delaying the realization of outstandingly superior 4H-SiC power electronics. While efforts to date have centered on eradicating micropipes (i.e., hollow core super-screw dislocations with Burgers vector>2 c ), 4H-SiC wafers and epilayers also contain elementary screw dislocations (i.e., Burgers vector=1 c with no hollow core) in densities on the order of thousands per cm 2 , nearly 100-fold micropipe densities. This paper describes an initial study into the impact of elementary screw dislocations on the reverse-bias current–voltage ( I – V ) characteristics of 4H-SiC p + n diodes. First, synchrotron white beam X-ray topography (SWBXT) was employed to map the exact locations of elementary screw dislocations within small-area 4H-SiC p + n mesa diodes. Then the high-field reverse leakage and breakdown properties of these diodes were subsequently characterized on a probing station outfitted with a dark box and video camera. Most devices without screw dislocations exhibited excellent characteristics, with no detectable leakage current prior to breakdown, a sharp breakdown I – V knee, and no visible concentration of breakdown current. In contrast, devices that contained at least one elementary screw dislocation exhibited 5–35% reduction in breakdown voltage, a softer breakdown I – V knee, and visible microplasmas in which highly localized breakdown current was concentrated. The locations of observed breakdown microplasmas corresponded exactly to the locations of elementary screw dislocations identified by SWBXT mapping. While not as detrimental to SiC device performance as micropipes, the undesirable breakdown characteristics of elementary screw dislocations could nevertheless adversely affect the performance and reliability of 4H-SiC power devices.

Structural dependence of dielectric breakdown in ultra-thin gate oxides and its relationship to soft breakdown modes and device failure

Abstract: For the first time, we report strong channel-length dependence and weak channel-width dependence of soft breakdown modes and device failure for ultra-thin gate oxides For channel lengths around 02 /spl mu/m, oxide-breakdown events in FETs cause a sharp increase in FETs off-current which permanently degrades the switching performance of short-channel devices; this is not observed for longer channel length FETs The results also indicate that both hard- and soft-breakdown events have a common origin but manifest themselves differently depending on the test structure and geometry being measured

Vacuum-surface flashover switch with cantilever conductors

Abstract: A dielectric-wall linear accelerator is improved by a high-voltage, fast rise-time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators. A high voltage is placed between the electrodes sufficient to stress the voltage breakdown of the insulator on command. A light trigger, such as a laser, is focused along at least one line along the edge surface of the laminated alternating layers of isolated conductors and insulators extending between the electrodes. The laser is energized to initiate a surface breakdown by a fluence of photons, thus causing the electrical switch to close very promptly. Such insulators and lasers are incorporated in a dielectric wall linear accelerator with Blumlein modules, and phasing is controlled by adjusting the length of fiber optic cables that carry the laser light to the insulator surface.

Fabrication method of lateral double diffused MOS transistors

Abstract: According to a method for manufacturing double RESURF (reduced SURface Field) LDMOS (Lateral Diffused Metal Oxide Semiconductor) transistors, on-resistance of double RESURF LDMOS transistors has been improved by using a new tapered p top layer on the surface of the drift region of the transistor, thereby decreasing the length of the drift region. Another advantage of the current invention is that the breakdown voltage similar with the on-resistance can be improved by using a reproducible tapered TEOS oxide by use of a multi-layer structure and low temperature annealing process. This is due to the reducing of the current path and impurity segregation in the drift region by using the tapered TEOS oxide instead of LOCOS filed oxide.

A 3 kV Schottky barrier diode in 4H-SiC

Abstract: High-voltage Schottky barrier diodes with low reverse leakage current were processed on hot-wall chemical vapor deposition grown 4H-SiC films. A metal overlap onto the oxide layer was employed to reduce electric field crowding at the contact periphery. By utilizing a 42–47 μm thick, high-quality epitaxial layers with doping in the range of 7×1014–2×1015 cm−3, a record blocking voltage of above 3 kV was achieved. The large diodes with 1.0 mm diameter showed breakdown at 2.1 kV. The reverse leakage current density at 1.0 kV was measured to be 7.0×10−7 A cm−2. Specific on-resistance of the diode with breakdown voltage at 3 kV was 34 mΩ cm2.

Conversion of methane to higher hydrocarbons in AC nonequilibrium plasmas

Abstract: The effects of plasma chemistry on the conversion of methane were studied using a dielectric barrier discharge reactor at ambient temperatures. A dielectric barrier discharge reactor generates a nonequilibrium plasma when a sufficiently high voltage is applied across the reactor`s electrodes. Methane molecules are activated at this temperature and coupled to form C{sub 2} hydrocarbons, higher hydrocarbons, and hydrogen. The study on the effect of voltage, residence time and third bodies on methane conversion and product selectivity shows that methane conversion initially increases with increasing voltage and residence time above the breakdown voltage, and product selectivities are essentially independent of the voltage. Production of hydrogen during the reaction limits olefin production. Methane conversion also increases when helium and ethane are in the feed stream. Helium and ethane both appear to be more easily activated than methane and enhance methane activation and conversion.

A high voltage thin film transistor with improved on-state characteristics and method for making same

Abstract: The present invention is directed to an SOI LDMOS device having improved current handling capability, particularly in the source-follower mode, while maintaining an improved breakdown voltage capability. The improvement in current handling capability is achieved in a first embodiment by introducing an offset region between the source and thin drift regions. The offset region achieves an offset between the onset of the linear doping profile and the thinning of the SOI layer that results in the thin drift region. In a second embodiment a further increase in the current handling capability of an SOI device is achieved by fabricating an oxide layer over the offset region, with the thickness of the oxide layer varying up to about half the thickness of the oxide layer fabricated over the thin drift region.

Static and dynamic characterization of large-area high-current-density SiC Schottky diodes

Abstract: The static and dynamic characteristics of large-area, high-voltage 4H-SiC Schottky barrier diodes are presented. With a breakdown voltage greater than 1200 V and a forward current in excess of 6 A at 2 V forward bias, these devices enable for the first time the evaluation of SiC Schottky diodes in practical switching circuits. These diodes were inserted into standard test circuits and compared to commercially available silicon devices, the results of which are reported here. Substituting SiC Schottky diodes in place of comparably rated silicon PIN diodes reduced the switching losses by a factor of four, and virtually eliminated the reverse recovery transient. These results are even more dramatic at elevated temperatures. While the switching loss in silicon diodes increases dramatically with temperature, the SiC devices remain essentially unchanged. The data presented here clearly demonstrates the distinct advantages offered by SiC Schottky rectifiers, and their emerging potential to replace silicon PIN diodes in power switching applications.

Output buffer circuit having low breakdown voltage

Abstract: In an output buffer circuit, a logic circuit generates first and second data signals each having a voltage level between a low voltage and a first high voltage. A level shift circuit receives the first data signal and generates a third data signal having a voltage between a first intermediate voltage and a second high voltage higher than the first high voltage. An output circuit includes first and second P-channel MOS transistors and first and second N-channel MOS transistors powered by the low voltage and the second high voltage, a gate of the first P-channel MOS transistor receives the third data signal, a gate of the second P-channel MOS transistor receives a second intermediate voltage between the low voltage and the second high voltage, a gate of the first N-channel MOS transistor receives the data signal, and a gate of the second N-channel MOS transistor receives a third intermediate voltage.

High voltage subnanosecond breakdown

Abstract: Present-day ultra-wideband radiation sources produce Megavolt pulses at hundreds of picosecond (ps) risetimes. Empirical data on the breakdown characteristics for dielectric media at these short time lengths and high voltages are either extremely limited or nonexistent. In support of the design of these ultra-wideband sources, we are investigating the breakdown characteristics, at these voltages and time lengths, of several liquids and high-pressure gases. These include air, N/sub 2/, H/sub 2/, SF/sub 6/, and transformer oil. Gap voltages attained were over 700 kV and gas pressures were over 150 atm (15 MPa). Breakdown times achieved were on the order of 600 ps. Electric field strengths observed for given breakdown times were higher than predicted by other investigators. An empirical fit is presented for the data obtained.

Arcing and voltage breakdown in vacuum microelectronics microwave devices using field emitter arrays: Causes, possible solutions, and recent progress

Abstract: There is growing interest in high current field emitter arrays (FEAs) capable of delivering high current density and high conductance electron beams, particularly for microwave applications. Large, high packing density molybdenum and silicon FEAs have been placed in ultrahigh vacuum chambers, carefully conditioned, and tested for maximum performance and have yielded total FEA currents of 20–200 mA and beam current densities of 5–2000 A/cm2 at gate voltages of 80–150 V. However similar Mo and Si FEAs, and GaAs edge arrays, when placed in a prototype 10 GHz klystrode amplifier, have failed at 1–4 mA, even for pulsed operation at a low duty factor. Hence, the current must be increased by 25–50 in order to meet klystrode design objectives. We compare the intrinsic FE stable current limits of various materials: Mo, Si, GaAs, ZrC, and ZrC films on Mo emitters. We conclude that Mo FEAs have a high FE current limit but demand an extremely clean environment, Si or GaAs FEAs are more tolerant of a poorer environmen...

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

Abstract: 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.

Scientific and technological progress of pseudospark devices

Abstract: This paper presents an overview on the state-of-the-art of research and development with pseudospark devices. There is an ongoing interest worldwide in this novel low pressure gas discharge device. This is proven by the several papers recently published. Careful studies of breakdown characteristics with two-electrode pseudospark devices show that the simple relation of the old Paschen law is modified for this geometry. Especially for operating the pseudospark reliably at low gas pressure, it is necessary to superimpose external magnetic fields to initiate the discharge. At low pressure intense beam formation is enhanced but in parallel is hampered by less efficient space-charge-neutralization. Based on the original pseudospark geometry several modified beam configurations were developed like the channel spark and the preionization-controlled open-ended hollow cathode system. In pulsed electrical circuits for discharge currents below 10 kA, distinct discharge phenomena appear which have to be suppressed for any application. One of these is transient impedance transition, correlated with steps in forward voltage drop. By geometry and choice of electrode material the irregular transitions in impedance can be controlled over a wide parameter range. Another annoying effect is quenching obvious by sudden and irregular interruption of the discharge current. Quenching is observed as a random effect, which is influenced by a manifold of parameters. Results from the experiment indicate that quenching is strongly dependent on the number density of gas atoms in the discharge volume. Since silicon carbide (SiC) as part of the switch electrode downsizes the quenching current to negligible values (<1 kA) optical spectroscopy was used to investigate the influence of this semiconducting material on the temporal development of the discharge, by looking for emission lines of the released silicon and/or carbon atoms. The technological aspects of pseudospark devices are naturally to achieve higher lifetime and improved overall reliability. Multichannel configurations and two-gap systems are under development to reduce erosion rate and to increase hold-off capability, respectively. Under clean conditions a hold-off voltage of 65 kV was realized by a two-gap system.

Bias voltage control circuitry for avalanche photodiode taking account of temperature slope of breakdown voltage of the diode, and method of adjusting the same

Abstract: Circuitry capable of controlling a bias voltage for an avalanche photodiode (APD) in accordance with the temperature slope of the breakdown voltage of the APD is disclosed. A reference voltage generating circuit sets a voltage implementing an optimal amplification ratio on an output terminal, and generates a reference voltage by taking account of the temperature slope of the breakdown voltage of the APD. The reference voltage is applied to one input of a voltage comparator. A setting circuit feeds to an adding circuit a preselected voltage for controlling the voltage on the output terminal to a value capable of implementing the optimal multiplication ratio. A temperature compensating circuit feeds to the adding circuit a voltage corresponding to the temperature slope of the above breakdown voltage. The temperature slope is representative of the variation of the breakdown voltage with respect to temperature. The adding circuit adds the two input voltages and delivers its output to the voltage comparator as the reference voltage. The voltage comparator produces a difference between the reference voltage and a voltage input from the output terminal and outputs a voltage control signal representative of the difference.

SiC Merged p-n/Schottky Rectifiers for High Voltage Applications

Abstract: A method of reducing reverse currents and increasing breakdown voltages without inducing negative effects on switching behavior in silicon carbide Schottky diodes is proved successfully. Implantation of p-regions in the surface of the n-drift region below the Schottky metal form face to face p-n junctions which screen the Schottky contact from high electrical fields. This results in a reduction of the reverse current and an increase of the breakdown voltage to the limit of a `pure` SiC p-n diode. It is shown, that in contrast to silicon based devices, SiC merged p-n/Schottky (MPS) rectifier preserve their excellent unipolar switching behavior. (orig.) 5 refs.