Search

The forward and reverse bias dc characteristics, the long-term stability under forward and reverse bias and the reverse recovery performance of 4H-SiC junction barrier Schottky (JBS) diodes that are capable of blocking in excess of 10 kV with forward conduction of up to 10 A at a forward voltage of less than 3.5 V are described. The diodes have shown a positive temperature coefficient of resistance and a stable Schottky barrier height of up to 200 degree centigrade.

A compact circuit simulator model is used to describe the performance of a 2-kV, 5-A 4-H silicon carbide (SiC) power DiMOSFET and to perform a detailed comparison with the performance of a widely used 400-V, 5-A Si power MOSFET. The model's channel current expressions are unique in that they include the channel regions at the corners of the square or hexagonal cells that turn on at lower gate voltages and the enhanced linear region transconductance due to diffusion in the nonuniformly doped channel. It is shown that the model accurately describes the static and dynamic performance of both the Si and SiC devices and that the diffusion-enhanced channel conductance is essential to describe the SiC DiMOSFET on-state characteristics. The detailed device comparisons reveal that both the on-state performance and switching performance at 25 [degrees]C are similar between the 400-V Si and 2-kV SiC MOSFETs, with the exception that the SiC device requires twice the gate drive voltage. The main difference between the devices is that the SiC has a five times higher voltage rating without an increase in the specific on-resistance. At higher temperatures (above 100 [degrees]C), the Si device has a severe reduction in conduction capability, whereas the SiC on-resistance is only minimally affected. Index Terms--DiMOSFET, silicon carbide (SIC).

1. Introduction A Complementary Metal-Oxide Semiconductor (CMOS) microhotplate-based gas-sensor SoC (System on a Chip) currently under development (2) requires sub-micron integrated-circuit (IC) technology to provide the desired level of performance […]

Dynamic electrothermal circuit simulator models are developed for silicon carbide power diodes. The models accurately describe the temperature dependence of on-state characteristics and reverse-recovery switching waveforms. The models are verified for the temperature dependence of the on-state characteristics, and the di/dt, dv/dt, and temperature dependence of the reverse-recovery characteristics. The model results are presented for 1500 V SiC Merged PiN Schottky (MPS) diodes, 600 V Schottky diodes, and 5000 V SiC PiN diodes. The devices studied have current ratings from 0.25 A to 5 A and have different lifetimes resulting in different switching energy versus on-state voltage trade-offs. The devices are characterized using a previously reported test system specifically designed to emulate a wide range of application conditions by independently controlling the applied diode voltage, forward diode current, di/dt, and dv/dt at turn-off. A behavioral model of the test system is implemented to simulate and validate the models. The models are validated for a wide range of application conditions for which the diode could be used. Index Terms--Circuit simulation, diode model, merged PiN Schottky, PiN, power diode, reverse recovery, Schottky, SiC.

The design, fabrication and high temperature characteristics of 4H-SiC p-i-n rectifiers are described. The results were achieved from two lots in order to increase the total power levels on the rectifiers.

The 4H-SiC JBS diode offers nearly zero reverse-recovery charge. The use of the SiC JBS diode in hard switching applications eliminates the reverse recovery and the associated transistor turn-on current, as indicated by the experimental results.

The significance of interconnect parasitics of power electronics systems is their effects on converters' electromagnetic interference (EMI)-related performances, such as voltage/current spikes, dv/dt,di/dt, conducted/radiated EMI noise, etc. In this paper, a time domain reflectometry (TDR) measurement-based modeling technique is described for characterizing interconnect parasitics in switching power converters. Experiments are conducted on power components of a prototype high-power inverter, including insulated gate bipolar transistor (IGBT) modules, busbar, and bulk capacitors. It is shown that the interconnect inductance of the IGBT module can be extracted completely using TDR. It is also shown that the busbar equivalent circuit can be modeled as transmission line segments or L-C filter sections, and the bulk capacitor contains a significant equivalent series interconnect inductance. Index Terms: Device packaging, IGBT model, interconnect parasitics, power inverter, time domain reflectometry.

A recently developed electrothermal network simulation methodology is used to analyze the behavior of a full-bridge, pulse-width-modulated (PWM), voltage-source inverter, which uses insulated gate bipolar transistors (IGBT's) as the switching devices. The electrothermal simulations are performed using the Saber circuit simulator and include control logic circuitry, IGBT gate drivers, the physics-based IGBT electrothermal model, and thermal network component models for the power-device silicon chips, packages, and heat sinks. It is shown that the thermal response of the silicon chip determines the IGBT temperature rise during the device switching cycle. The thermal response of the device TO247 package and silicon chip determines the device temperature rise during a single phase of the 60-Hz sinusoidal output. Also, the thermal response of the heat sink determines the device temperature rise during the system startup and after load-impedance changes. It is also shown that the full electrothermal analysis is required to accurately describe the power losses and circuit efficiency. Index Terms - Electrothermal, IGBT, inverter, modeling, pulse-width modulation, simulation.

The dynamic behavior of commercially available buffer layer IGBT's is described. It is shown that buffer layer IGBT's become much faster at high voltages than nonbuffer layer IGBT's with similar low voltage characteristics. Because the fall times specified in manufacturers' data sheets do not reflect the voltage dependence of switching speed, a new method of selecting devices for different circuit applications is suggested. A buffer layer IGBT model is developed and implemented into the Saber circuit simulator, and a procedure is developed to extract the model parameters for buffer layer IGBT's. It is shown that the new buffer layer IGBT model can be used to describe the dynamic behavior and power dissipation of buffer layer IGBT's in user-defined application circuits. The results of the buffer layer IGBT model are verified using commercially available IGBT's.

A physics-based IGBT model is implemented into the general purpose circuit simulator Saber[TM]. The IGBT model includes all of the physical effects that have been shown to be important for describing IGBT's, and the model is valid for general external circuit conditions. The Saber IGBT model is evaluated for the range of static and dynamic conditions in which the device is intended to be operated, and the simulations compare well with experimental results for all of the conditions studied.

Theoretical study enables the development of a methodology for developing thermal component models for electrothermal network simulation. A simulator in this methodology helps solve current and voltage distribution within the electrical network and the temperature distribution within the semiconductor devices, heat sinks and packages. Measurement of temperature within the thermal network by different techniques helps validate the thermal component models.

A physics-based dynamic electro-thermal model is developed for the IGBT by coupling a temperature-dependent IGBT electrical model with dynamic thermal models for the IGBT silicon chip, packages, and heatsinks. The temperature-dependent IGBT electrical model describes the instantaneous electrical behavior in terms of the instantaneous temperature of the IGBT silicon chip surface. The instantaneous power dissipated in the IGBT is calculated using the electrical model and determines the instantaneous rate that heat is applied to the surface of the silicon chip thermal model. The thermal models determine the evolution of the temperature distribution within the thermal network and thus determine the instantaneous value of the silicon chip surface temperature used by the electrical model. The IGBT electro-thermal model is implemented in the Saber circuit simulator and is connected to external circuits in the same way as the previously presented Saber IGBT model, except that it has an additional thermal terminal that is connected to the thermal network component models for the silicon chip, package, and heatsink. The IGBT dynamic electro-thermal model and the thermal network component models are verified for the range of temperature and power dissipation levels (heating rates) that are important for power electronic systems.

A physics-based model for the Insulated Gate Bipolar Transistor (IGBT) is implemented into the widely available circuit simulation package IG-SPICE. Based on analytical equations describing the semiconductor-physics, the model accurately describes the nonlinear junction capacitances, moving boundaries, recombination, and carrier scattering, and effectively predicts the device conductivity modulation. In this paper, the procedure used to incorporate the model into IG-SPICE and various methods necessary to ensure convergence are described. The effectiveness of the SPICE-based IGBT model is demonstrated by investigating the static and dynamic current sharing of paralleled IGBTs with different device model parameters. The simulation results are verified by comparison with experimental results.

A methodology is presented for simulating the dynamic electrothermal behavior of power electronic circuits and systems. In the approach described, the simulator solves for the temperature distribution within the semiconductor devices, packages, and heatsinks (thermal network) as well as the currents and voltages within the electrical network. The thermal network is coupled to the electrical network through the electrothermal models for the semiconductor devices. The electrothermal semiconductor device models calculate the electrical characteristics based upon the instantaneous value of the device silicon chip surface temperature and calculate the instantaneous power dissipated as heat within the device. The thermal network describes the flow of heat from the chip surface through the package and heatsink and thus determines the evolution of the chip surface temperature used by the semiconductor device models. The thermal component models for the device silicon chip, packages, and heatsinks are developed by discretizing the nonlinear heat diffusion equation and are represented in component form so that the thermal component models for various packages and heatsinks can be readily connected to one another to form the thermal network.

For the study of electromagnetic interference (EMI) mechanisms in pulsewidth-modulated inverters, this paper presents an analysis approach based on empirical models of the inverter components and their associated various parasitics. The power switching devices were modeled with a physics-based device modeling technique. Using time-domain reflectometry, we characterized the major parasitics in the device modules, passive components, cables, leads, and interconnects. Simulations of a full-bridge insulated gate bipolar transistor inverter were then carried out in the time domain under hard-switching and zero-voltage switching conditions. The simulated EMI spectra were compared with the experimental counterparts with the separation of common-mode and differential-mode EMI. The comparisons verified the validity of the proposed modeling approach over most of the EMI frequency range. Also discussed in the paper are the soft-switching effects on the inverter's EMI. Index Terms--Device modeling, electromagnetic interference, parasitic components, pulsewidth-modulated inverter, soft switching, time-domain reflectometry.

Techniques are described for validating the performance of insulated gate bipolar transistor (IGBT) circuit simulator models for soft-switching circuit conditions. The circuits used for the validation include a soft-switched boost converter similar to that used in power-factor correction, and a new half-bridge testbed that is specially designed to examine the details of IGBT soft-switching waveforms. The new testbed is designed to emulate the soft-switching circuit conditions of actual applications circuits, while allowing the easy change of IGBT operating conditions. The testbed also eliminates the problems of commutating diode noise and IGBT temperature rise found in actual application circuits. Simulations of IGBT models provided in circuit simulator component libraries are compared with measurements obtained using these test circuits for the soft-switching conditions of zero-voltage turn-on, zero-voltage turn-off, or zero-current turn-off. Finally, the results are summarized by comparing the switching energies for the various measurements and simulations presented in this work. Index Terms--Circuit simulation, insulated gate bipolar transistor, model validation, power electronics, soft switching, switching energy.

The electrical performance of silicon carbide (SiC) power diodes is evaluated and compared to that of commercially available silicon (Si) diodes in the voltage range from 600 V through 5000 V. The comparisons include the on-state characteristics, the reverse recovery characteristics, and power converter efficiency and electromagnetic interference (EMI). It is shown that a newly developed 1500-V SiC merged PiN Schottky (MPS) diode has significant performance advantages over Si diodes optimized for various voltages in the range of 600 V through 1500 V. It is also shown that a newly developed 5000 V SiC PiN diode has significant performance advantages over Si diodes optimized for various voltages in the range of 2000 V through 5000 V. In a test case power converter, replacing the best 600 V Si diodes available with the 1500 V SiC MPS diode results in an increase of power supply efficiency from 82% to 88% for switching at 186 kHz, and a reduction in EMI emissions. Index Terms--Fast recovery rectifier, merged PiN Schottky diode, PiN diode, reverse recovery, SiC diode, SiC rectifier.

Certain applications for pulse power require narrow, high current pulses for their implementation. This work was performed to determine if MOS controlled thyristors (MCTs) could be used for these applications. The MCTs were tested as discharge switches in a low inductance circuit delivering 1[micro]s pulses at currents between roughly 3 kA and 11kA, single shot and repetitively at 1, 10, and 50 Hz. Although up to 9000 switching events could be obtained, all the devices failed at some combination of current and repetition rate. Failure was attributed to termperature increases caused by average power dissipated in the thyristor during the switching sequence. A simulation was performed to confirm that the temperature rise was sufficient to account for failure. Considerable heat sinking, and perhaps a better thermal package, would be required before the MCT could be considered for pulse power applications. Index Terms--High power, power semiconductor switching, reliability, repetitive pulsing.

The internal failure dynamics of the insulated gate bipolar transistor (IGBT) for unclamped inductive switching (UIS) conditions are studied using simulations and measurements. The UIS measurements are made using a unique, automated nondestructive reverse-bias safe operation area test system. Simulations are performed with an advanced IGBT circuit simulator model for UIS conditions to predict the mechanisms and conditions for failure. It is shown that the conditions for UIS failure and the shape of the anode voltage avalanche-sustaining waveforms during turn-off vary with the IGBT temperature, and turn-off current level. Evidence of single- and multiple-filament formation is presented and supported with both measurements and simulations. Index Terms--Avalanche, current constriction, failure, filament, insulated gate bipolar transistor, modeling, nondestructive testing, reverse-bias safe operation area.

Semiconductor die-attach techniques are critically important in the implementation of high-temperature wide-bandgap power devices. In this paper, thermal and mechanical characteristics of Au-In transient liquid phase (TLP) die-attach are examined for SiC devices. Samples with SiC diodes TLP-bonded to copper-metalized silicon nitride substrates are made using several different values for such fabrication properties as gold and indium thickness, Au/In ratio, and bonding pressure. The samples are then characterized for die-attach voiding, shear strength, and thermal impedance. It is found that the Au-In TLP-bonded samples offer a high average shear strength of 22.0 kgf and a low average thermal impedance of 0.35 K/W from the device junction through the substrate. It is also discovered that some of the fabrication properties have a greater influence on the bond characteristics than others. Overall, TLP bonding remains promising for high-temperature power electronic die-attach. [ABSTRACT FROM PUBLISHER]

10 kV, 123 mΩ·cm² Power DMOSFETs in 4H-SiC are demonstrated. A 42% reduction in Ron,sp, compared to a previously reported value, was achieved by using an 8 × 1014 cm-3 doped, 85-µ-thick drift epilayer. An effective channel mobility of 22 cm²/Vs was measured from a test MOSFET. A specific on-resistance of 123 mΩ·cm² were measured with a gate bias of 18 V, which corresponds to an Eox of 3 MV/cm. A leakage current of 197 µA was measured at a drain bias of 10 kV from a 4H-SiC DMOSFET with an active area of 4.24 × 10-3 cm². A switching time of 100 ns was measured in 4.6-kV, 1.3-A switching measurements. This shows that the 4H-SiC power DMOSFETS are ideal for high-voltage, high-speed switching applications. [ABSTRACT FROM AUTHOR]