High‐Power Semiconductor Devices

This paper presents a three-dimensional (3-D) wire bondless power module using silicon carbide (SiC) power devices. Commercially available SiC power devices are designed for wire bonding. Wire bonds have an inherent parasitic inductance that limits high-frequency switching. This results in an underutilization of the full potential of SiC power devices, which have very low switching losses at high frequencies. Wire-bonded power modules run into a performance ceiling when it comes to ultrafast switching. This paper strives to provide a solution to this issue, which involves reconfiguring a commercially available bare die SiC power device into a flip-chip-capable device. A wire bondless SiC Schottky diode package was demonstrated and its performance was contrasted with a conventional wire-bonded package. A 24% reduction in the ON-state resistance was observed in the wire bondless package. As a next step, wire bondless SiC MOSFET packages were developed and tested in a half-bridge configuration in a highly integrated 3-D arrangement. This approach departs from the conventional concept of a power module—demonstrating a direct-bonded-copper-less and baseplate-less half-bridge switching cell. Double-pulse tests conducted on the cell showed >3× reduction in the parasitic inductance of the 3-D cell as compared with a conventional wire-bonded module.

Photovoltaic (PV) energy conversion systems require fast-switching power devices that are highly efficient with low semiconductor loss under harsh environmental conditions. Silicon (Si) semiconductor devices are nearing their practical limits in meeting the ever-increasing requirements of power converters. However, wide bandgap (WBG) semiconductor devices made from silicon carbide (SiC) are exceeding these limits. SiC power devices enable more efficient and higher performance power converters. This paper presents a non-isolated dc-dc boost converter based on SiC power devices optimized for use in PV systems. The performance of two otherwise identical converters is compared, one with a new SiC MOSFET/SiC Schottky diode, and one with a conventional Si MOSFET/Si diode. A comparison of switching characteristics and energy loss of each semiconductor device is performed at different switch currents. Converter total loss and overall efficiency are evaluated at different switching frequencies, input voltages, and output power levels. The results indicate that the SiC MOSFET/SiC Schottky diode in the converter is more efficient, performs better, and has reduced power loss compared to the Si MOSFET/Si diode.

In this paper, a technology computer-aided design (TCAD) model of a silicon carbide (SiC) insulated-gate bipolar transistor (IGBT) has been calibrated against previously reported experimental data. The calibrated TCAD model has been used to predict the static performance of theoretical SiC IGBTs with ultra-high blocking voltage capabilities in the range of 20-50 kV. The simulation results of transfer characteristics, IC-VGE, forward characteristics, IC-VCE, and blocking voltage characteristics are studied. The threshold voltage is approximately 5 V, and the forward voltage drop is ranging from VF = 4.2-10.0 V at IC = 20 A, using a charge carrier lifetime of τA = 20 μs. Furthermore, the forward voltage drop impact for different process dependent parameters (i.e., carrier lifetimes, mobility/scattering and trap related defects) and junction temperature are investigated in a parametric sensitivity analysis. The wide-range simulation results may be used as an input to facilitate high power converter design and evaluation. In this case, the TCAD simulated static characteristics of SiC IGBTs is compared to silicon (Si) IGBTs in a modular multilevel converter in a general high-power application. The results indicate several benefits and lower conduction energy losses using ultra-high voltage SiC IGBTs compared to Si IGBTs.

Silicon-Carbide (SiC) power devices have become the prime candidates for future high-performance energy conversion on account of their superior performance over traditional silicon power devices. The superior electro-thermal properties of SiC power devices permit higher temperature of operation and enable higher power density. Nevertheless, the high operation temperature has introduced new changes in die attachment packaging of the SiC power device, which is one of the most vulnerable places due to a direct connection to the SiC chip. Traditional Pb-free solder-joining is hardly to withstand high temperatures because of the low melting point of solder materials. Besides, severe temperature swings of the SiC chip can introduce severe deterioration in the solder layer due to brittle alloy compounds. Currently, Ag sinter-joining is an ideal connection technique for high reliable power electronics packaging. Due to excellent thermal stability and chemical resistance, the Ag sinter-joining is applicable to various harsh conditions, such as extreme temperatures, high humidity, high heavy current, etc., showing promising application scenarios in die attachment packaging. In this work, we applied Ag sinter-joining to die attachment of a molded SiC device and focused reliability of Ag sinter joining under harsh thermal cycling and power cycling conditions. The SiC device was assembled by a SiC diode and direct bonding copper (DBC) substrate via the Ag sinter-joining. Ribbon bonding was used for the topside connection of the SiC device. An imide resin was applied to mold the SiC device. The thermal cycling test was conducted at a temperature range from -50 °C to 200 °C and the power cycling test was conducted at an initial junction of 200 °C. The structures inspection, thermal resistance variations, and voltage-current curve were investigated to understand failures in the SiC device. The thermal cycling can introduce crazing cracks in the sintered layer due to drastic thermal stress caused by a huge temperature swing. However, the thermal resistance, of the SiC device measured by T3ster, was not significantly affected by the crazing pattern. The Ag sinter-joining also shows an excellent resistance during the power cycling test, while the ribbon lift-off will introduce a final failure of the SiC device. Figure 1 shows a cross section of the structure of the SiC power device with and without a power cycling test. Obvious cracks can be differentiated at the ribbon bonding interface after cycling, while there is no deterioration happened in the sintered Ag layer. Base on the present results, it can be concluded that the Ag sinter-joining can withstand a harsh cycling condition either in huge temperature swings or heavy currents. Figure 1

: Due to the magnificent properties of Silicon Carbide (SiC), such as high saturation drift velocity, large operating temperature, higher cut-off and maximum frequency (fT and fmax), high thermal conductivity and large breakdown voltages (BV), it is desirable for high power electronics. With the latest advancements in semiconductor materials and processing technologies, diverse high-power applications such as inverters, power supplies, power converters and smart electric vehicles are implemented using SiC-based power devices. Especially, SiC MOSFETs are mostly used in high-power applications due totheir capability to achieve lower switching loss, higher switching speed and lower ON resistance than the Si-based (Insulated gate bipolar transistor) IGBTs. In this paper, a critical study of SiC MOSFET architectures, emerging dielectric techniques, mobility enhancement methods and irradiation effects are discussed. Moreover, the roadmap of Silicon Carbide power devices is also briefly summarized.

In this paper, thermal impedances of Silicon carbide (SiC) power module assembled with a Schottky Barrier Diode (SBD)–wall–integrated trench MOSFET (SWITCH–MOS) and a conventional trench gate MOSFET (UMOS) are measured. Then they are compared to show the advantage of SWITCH–MOS for thermal impedance measurement. SiC power device is attracting attention as a candidate for future power device, since it can be operated at higher current density and higher switching speed than conventional silicon (Si) power device. The power module packaging technology for SiC power device should have low thermal impedance (both transient and steady state thermal resistance) to bring out a potential ability of the device. Thermal design often has difference from measurement due to various modeling errors such as power device heat generation, module structure, interfacial thermal resistance, and cooling environment. Therefore, accurate thermal impedance measurement is an essential technology. However, the thermal impedance measurement of SiC power modules has the significant issue due to the instability of the body diode built into the SiC–MOSFET. The thermal impedance is the junction temperature rise per heat generation amount of the device. The temperature dependence of the knee voltage of the body diode is used to measure the junction temperature of the MOSFET. Since the knee voltage of SiC–MOSFET changes depending on the gate voltage, a high negative gate bias was necessary to avoid this effect. However, the negative gate bias stress may cause serious device damage such as threshold shift. The SWITCH–MOS which has SBD built in near the MOSFET channel is expected to stabilize the junction temperature measurement and avoid the risk of device deterioration. Figure 1 shows the cross–sectional schematic of the SWITCH–MOS and the conventional UMOS. The SBD are formed on the trench sidewall in SWITCH-MOS, and the device structure is almost same to the UMOS. The temperature is detected by the PiN diode for the UMOS and by the SBD for the SWITCH–MOS. Both of them measure the temperature inside of the MOSFET cell. The appearance of the test module is shown in Fig. 2. Each type of the test module is composed of the SiC die (SWITCH–MOS, UMOS, and SBD), an SiN–AMC insulating circuit substrate and an Al baseplate. The components are attached each other using AuGe solder. The junction temperature is measured from the built–in voltage of the body diode in response to a constant current flowing from the source to the drain. In the case of the UMOS, the gate bias of −18 V is applied. The gate bias is zero for the SWITCH–MOS. The thermal impedance of each test module was measured by static mode (Fig. 3). Then, the thermal structure function was calculated by transient thermal analysis (Fig. 4). Both the thermal impedance and the structure function for the SWITCH–MOS and UMOS were in good agreement. Since the SWITCH–MOS does not need negative gate bias, the threshold shift issue does not occur in principle. In addition, it is possible to perform a transient thermal testing with a large current for a long time. Because the forward degradation does not occur even if a large current is applied to the SBD in the SWITCH–MOS. The SBD built into the SWITCH–MOS makes it easier and more accurate to measure the junction temperature of the SiC–MOSFET. The thermal impedance measurement using SWITCH-MOS not only allows the precise thermal modeling of SiC power modules to be performed, but also has the potential to be applied to the calibration of the thermal design and the evaluation of thermal properties inside of the package structure. Figure 1

IGBT in power system has been dominating MOS (Metal Oxide Semiconductor) transistor since IGBTs (Insulated Gate Bipolar Transistor) guarantee better conduction loss and large current capacity. The radiation induced characteristics of IGBT are mainly emphasized the threshold shifting due to the oxide charge trapping in MOS and the reduction of current gain in the bipolar transistor being inherently composed in the IGBT structure. A lot of analysis on IGBT irradiation has been carried out by researchers. The IGBT in the converter plays an important role in switching. In this paper, the IGBT macro-model for the DC/DC converter is implemented and analyzed the electrical characteristics by SPICE simulation model. In addition, the design SPICE parameters of BF (forward beta), KP (MOS trans-conductance), and <i>V</i>_T (threshold voltage) by &gamma; radiation effects are evaluated.

This paper compares the conducted electromagnetic interference (EMI) in Si insulated gate bipolar transistor (IGBT) and silicon carbide (SiC) junction field-effect transistor (JFET) based motor drives. Two inverters, with the SiC and Si transistors, respectively, are built using the same circuit layout and investigated accordingly. Their conducted EMI levels are compared under the conditions of without filter and with traditional common mode (CM) filters. Reasons of the exhibited different noise emissions are analyzed. To verify the discussions, two inverters are tested in the CM. This allows for the identification and analysis of their maximized CM and differential mode (DM) wave shapes. It is shown that the excited parasitic oscillations during the switching transients are magnified more in the SiC JFET inverter, which is the main cause of the noise difference. Lastly, improved filtering solutions are proposed, which effectively suppressed the increased high-frequency noise due to the faster SiC switching speed.

ABSTRACTThree-phase converters using diode or silicon-controlled rectifier (SCR) are widely employed to convert the commercial AC supply to DC. Such converters inject harmonics into the power supply system and thereby distort supply system voltage waveform. A simple input current wave-shape improvement technique using a shunt-connected harmonic current compensator is presented in this work, intended to reduce the total harmonic distortion (THD) of input current of three-phase diode and SCR phase-controlled rectifiers operating with inductive loads, by matching them to the specific converter as a combined package. The compensator proposed here comprises of a three-limb voltage source converter using insulated-gate bipolar transistor, working on instantaneous current and voltage measurements of the compensator only and not of the load. The technique uses a simple feedforward control for AC source current harmonic compensation of rectifiers without monitoring the AC line currents, i.e. use of online computation. The proposed system is simulated and tested on a laboratory prototype. The measured input current THD values without additional line filters are found to be below 8.3%, which is within acceptable limits, proving that the new technique is capable of compensating predetermined current harmonics of diode or SCRs.

The results of experimental investigations of transient processes and static voltage distribution consideration in composite solid-state switch consisted of series connected insulated gate bipolar transistors (IGBT) under conditions of artificial operational factors distortion are presented. The stability of the series connected transistors assembly with no special balancing circuits or adaptive gate control was shown. In transient, reliable operation of the assembly supported by effect of voltage self-restriction across lagged devices, and due to tolerance of IGBT to short-circuit mode which bounded by the junction power dissipation efficiency. In voltage blocking mode the single transistor overheating does not upsets the balance of the series transistors assembly as a whole, because helps to negative temperature coefficient of IGBT the tendency to self-stabilizing is appear as consequence of dissipation power redistribution. The last require to presence of some operational voltage amplitude margin for a single IGBT in the switch design.

A novel gate drive circuit for insulated gate bipolar transistors (IGBTs) is presented which provides high-speed switching with attention to dV/dt requirements. It also provides pulse-by-pulse overcurrent protection through on-state voltage monitoring while sending out a fault signal to the control circuit. It also incorporates a backup overcurrent protection with shutdown and a trip signal feedback to the control circuit. It provides self-isolation in the event of IGBT destruction, possible self-derived power supply from the IGBT power terminal voltage, and direct mounting (including electrical contacts) in the form of a PCB onto an ISOTOP package IGBT, all resulting in a reliable and modular construction, easy for maintenance. Oscillograms from an experimental chopper circuit using a prototype drive circuit are presented. >

Silicon carbide (SiC) is enabling the next generation of semiconductor power devices, with performance orders-of-magnitude beyond silicon. The most important power switching device is the SiC power MOSFET, whose performance is limited by three main resistance elements: the channel, drift layer, and substrate. For blocking voltages in the range of 400-900V, substrate resistance is a major limitation. Wafer thinning is currently used to reduce the substrate resistance, but this also reduces the strength of the wafers. We report on a waffle substrate technique that relies on wafer thinning and inductively coupled plasma (ICP) etching to reduce the substrate resistance below levels achievable by thinning alone, while retaining the mechanical stability of a moderately-thinned substrate. This technique can be applied to any SiC device for which substrate resistance is a limitation.

Effects of silicon carbide MOSFETs on the efficiency and power quality of a microgrid-connected inverter

SummaryTurn-off semiconductor devices have vastly promoted modern power electronics during the last decade. Included are bipolar power transistors. Field Effect Transistors (MOSFETs), Gate Tun-off Thyristors (GTOs) and Insulated Gate Bipolar Transistors (IGBTs). Additional elements are Static Induction Transistors and Thyristors (SITs and SIThs) as well as MOS Controlled Thyristors (MCTs) for higher frequency applications.The prensent status of semiconductor power devices is discussed including switching behavior, losses, gate driver, snubber, overcurrent and protection. The standard control is nowadays pulse width modulation, Resonant circuits are growing in importance because they allow for higher frequency, lower storage components and transformers and reduction of switching losses in semiconductor devices, Main field of application are discussed and future trends given.

This paper investigates efficiency gains achieved using an 800 V DC bus and wideband gap silicon carbide (SiC) semiconductors for a light-duty electric vehicle (EV), rather than an insulated-gate bipolar transistor (IGBT) inverter with a 400 V bus as is commonly used for EVs. Analytical inverter loss models with 600 V and 1200 V IGBTs, and 1200 V hybrid SiC and 1200 V All-SiC semiconductors are incorporated into a Chevrolet Bolt EV model and simulated over standard drive cycles. Battery pack voltage variations throughout the drive cycles, as well as variations in junction temperature, resulted in 16 to 27 % increased loss compared to fixed voltage and temperature assumptions. To validate the models, experimental testing was performed on a 1200 V IGBT inverter and a 1200 V SiC inverter both powering 160+ kW rated traction machines. Experimentally measured loss was typically within 100 W of the model, demonstrating its accuracy. Going from a 400 V to an 800 V DC bus with IGBTs, EV range was modeled to increase 1.2 %, while an 800 V bus and all SiC inverter results in a range increase of 5.0%. An empirical loss model fitted to measured inverter data shows the analytical model estimates range within 6 km.