Materials Science Forum Vol. 924

Abstract: This paper presents an insight into the short circuit (SC) capability of Rohm’s discrete 1.2 kV, 80 mΩ state-of-the-art silicon carbide (SiC) double trench metal-oxide-semiconductor field effect transistor (MOSFET). SC measurements are performed to compare the behavior of Wolfspeed’s similarly rated 1.2 kV, 80 mΩ planar MOSFET with the Rohm trench devices. Short circuit withstand time (SCWT) of both designs under nominal operating conditions at room temperature is measured by performing destructive SC tests.

Abstract: Fast and accurate compact models of Silicon Carbide (SiC) power semiconductors are necessary for the development and optimization of SiC power integrated circuits. This paper presents a new physics based compact model for vertical SiC MOSFETs. The proposed model is able to accurately simulate device characteristics by iteratively calculating the surface potential under consideration of important material and geometry effects.

Abstract: The benefits of SiC devices for use in power electronics has been long understood, and over 25 years of sustained development in materials and devices has brought adoption to a tipping point [1,15]. It takes the confluence of many separate developments to build the necessary momentum for accelerated adoption, and we will examine these factors.

Abstract: Wide-bandgap power semiconductor devices offer enormous energy efficiency gains in a wide range of potential applications. As silicon-based semiconductors are fast approaching their performance limits for high power requirements, wide-bandgap semiconductors such as gallium nitride (GaN) and silicon carbide (SiC) with their superior electrical properties are likely candidates to replace silicon in the near future. Along with higher blocking voltages wide-bandgap semiconductors offer breakthrough relative circuit performance enabling low losses, high switching frequencies, and high temperature operation. ARPA-E’s SWITCHES program, started in 2014, set out to catalyze the development of vertical GaN devices using innovations in materials and device architectures to achieve three key aggressive targets: 1200V breakdown voltage (BV), 100A single-die diode and transistor current, and a packaged device cost of no more than ȼ10/A. The program is drawing to a close by the end of 2017 and while no individual project has yet to achieve all the targets of the program, they have made tremendous advances and technical breakthroughs in vertical device architecture and materials development. GaN crystals have been grown by the ammonothermal technique and 2-inch GaN wafers have been fabricated from them. Near theoretical, high-voltage (1700-4000V) and high current (up to 400A pulsed) vertical GaN diodes have been demonstrated along with innovative vertical GaN transistor structures capable of high voltage (800-1500V) and low R_ON (0.36-2.6 mΩ-cm2). The challenge of selective area doping, needed in order to move to higher voltage transistor devices has been identified. Furthermore, a roadmap has been developed that will allow high voltage/current vertical GaN devices to reach ȼ5/A to ȼ7/A, realizing functional cost parity with high voltage silicon power transistors.

Abstract: The reliability of SiC devices remains to be a field of hectic activity because it is one of the obstacles for the ubiquitous application of SiC devices. Without decades of field experience, reliability testing, especially accelerated testing, is the only way to obtain information on reliability during the projected lifespan of the devices. For silicon devices, such tests exist and they are canonized in internationally recognized test standards. For SiC devices, these standards have to be revised and/or supplemented with tests to capture SiC specific degradation mechanisms. On the one hand, this requires a detailed knowledge about the mechanisms but on the other hand, this also requires the mission profile of the devices. In fact, it is not the mission profile of the device that determines its reliability but the mission profile of the chip. This contribution reviews the standard silicon tests useful for SiC devices and looks into additional, SiC specific tests that have been proposed but not yet been recognized as standards.

Abstract: This paper presents a preliminary study of the impact of device electro-thermal parameter spread and temperature variation on the robustness of SiC MOSFET parallel multi-chip power switch architectures. Reference is made to 1200 V – 80 mΩ rated commercial devices. Some major parameters are identified and selected, presenting experimental evidence of their impact during transient overload events. An advanced physics-based simulation model is then employed to extend the analysis to a more comprehensive set of parameters and operational conditions.

Abstract: An experimental demonstration of an effective short circuit protection scheme for SiC MOSFETs is presented in this paper. Measurements of the static characteristics of the SiC device before and after the short circuit events were obtained to evince that the device remained in good health. An ultra-fast short circuit protection scheme is implemented given the observed lower short-circuit withstand of present SiC devices. It is shown that the integrity of the SiC device was protected after one-hundred short circuit events.

Abstract: In this paper, we present our latest results on 650 V 4H-SiC DMOSFET developments for dual-side sintered power modules in electric drive vehicles. A low specific on-resistance (R_sp,on) of 1.8 mΩ⋅cm² has been achieved on 650 V, 7 mΩ 4H-SiC DMOSFETs at 25°C, which increases to 2.4 mΩ⋅cm² at 150°C. For the first time, the DMOSFET chip is designed specifically for use in dual-side soldering and sintering processes, and a 650 V, 1.7 mΩ SiC DMOSFET multichip half bridge power module has been built using the wirebond-free assembly. Compared to a similarly rated Si IGBT module, the conduction and switching losses were reduced by 80% and ~50%, respectively.

Abstract: The overvoltage during hard switching limits the full utilization of devices due to higher blocking voltage requirement. The faster switching speed of SiC MOSFET worsens the trade-off, and the understanding of the overvoltage’s mechanism is crucial for the better utilization. In this paper, experimental characterizations on the influence of circuit parasitic parameters and gate resistances on overvoltage are performed. Furthermore, a SPICE-based device behavioral model is built and found to able to accurately predict the overvoltage. The same method could be applied to device rating selection in converter design.

Abstract: This paper develops 1200V, 50A full SiC half bridge power module, which embeds C snubber and gate resistors. Embedded C snubber suppresses surge voltage in fast switching operation, and gate resistors avoid gate oscillation of parallel connected SiC MOSFET in the module. 1MHz switching operation of developed module with 600V DC-link voltage is experimentally confirmed.