Materials Science Forum Vols. 679-680

Abstract: In this work, implantation-free 4H-SiC bipolar transistors with two-zone etched-JTE and improved surface passivation are fabricated. This design provides a stable open-base breakdown voltage of 2.8 kV which is about 75% of the parallel plane breakdown voltage. The small area devices shows a maximum dc current gain of 55 at Ic=0.33 A (JC=825 A/cm2) and VCESAT = 1.05 V at Ic = 0.107 A that corresponds to a low ON-resistance of 4 mΩ•cm2. The large area device shows a maximum dc current gain of 52 at Ic = 9.36 A (JC=312 A/cm2) and VCESAT = 1.14 V at Ic = 5 A that corresponds to an ON-resistance of 6.8 mΩ•cm2. Also these devices demonstrate a negative temperature coefficient of the current gain (β=26 at 200°C) and positive temperature coefficient of the ON-resistance (RON = 10.2 mΩ•cm2).

Abstract: This paper reports our recent study on 4H-SiC power bipolar junction transistors (BJTs) with deep mesa edge termination. 1200 V – 10 A 4H-SiC power BJTs with an active area of 4.64 mm2 have been demonstrated using deep mesa for direct edge termination and device isolation. The BJT’s DC current gain () is about 37, and the specific on-resistance (RSP-ON) is ~ 3.0 m-cm2. The BJT fabrication is substantially simplified and an overall 10% reduction in the device area is achieved compared to the multi-step JTE-based SiC-BJTs.

Abstract: 600V-30A 4H-SiC Junction Barrier Schottky（JBS）diodes were designed and fabricated using SiC epitaxy and device technology. SiC JBS diodes were packaged in Si IGBT module，and switching measurements were done at 125°C. As free-wheeling diode for Si IGBT, 600V SiC JBS diode was compared to 600V ultra-fast diode from International Rectifier. SiC diode achieved 90% recovery loss reduction and corresponding IGBT showed 30% lower turn-on loss. However, SiC JBS diode has larger on-state voltage drop due to small chip area. On-state power loss will be lowered by increasing SiC chip area.

Abstract: The measured turn-off waveforms of 4.5 kV SiCGTs by using electron irradiation with various electron doses are reported. The turn-off time decreased with an increase in the electron dose. Furthermore, the turn-off characteristics of SiCGTs with p-type drift layer, which assumed the various trap concentrations, are simulated. The relation between the turn-off characteristics and the trap is also investigated. The simulated results show good correlation to measured data and the simulated turn-off times decrease with an increase in the electron dose as well as measured data.

Abstract: A 4.1x4.1mm2, 100mΩ 1,2kV lateral channel vertical junction field effect transistor (LCVJFET) built in silicon carbide (SiC) from SiCED, to use as the active switch component in a high-temperature operation DC/DC-boost converter, has been investigated. The switching loss for room temperature (RT) and on-state resistance (Ron) for RT up to 170°C is investigated. Since the SiC VJFET has a buried body diode it is also ideal to use instead of a switch and diode setup. The voltage drop over the body diode decreases slightly with a higher temperature. A short-circuit test has also been conducted, which shows a high ruggedness.

Abstract: The wide band-gap of Silicon Carbide (SiC) makes it a material suitable for high temperature integrated circuits [1], potentially operating up to and beyond 450°C. This paper describes the development of a 15V SiC CMOS technology developed to operate at high temperatures, n and p-channel transistor and preliminary circuit performance over temperature achieved in this technology.

Abstract: MOSFET-based integrated circuits were fabricated on silicon carbide (SiC) substrates. SiC devices can operate at much higher temperatures than current semiconductor devices. Simple circuit components including operational amplifiers and common source amplifiers were fabricated and tested at room temperature and at 300°C. The common source amplifier displayed gain of 7.6 at room temperature and 6.8 at 300°C. The operational amplifier was tested for small signal open loop gain at 1kHz, measuring 60 dB at room temperature and 57 dB at 300°C. Stability testing was also performed at 300°C, showing very little drift at over 100 hours for the individual MOSFETs and the common source amplifier.

Abstract: The suitability of normally-off 4H-SiC MOSFETs for high temperature operation in logic gates is investigated. Fowler-Nordheim analysis shows a lowering of the effective tunneling barrier height at elevated temperatures. Trap assisted tunneling induced by carbon interstitials is proposed as the responsible mechanism. Nevertheless, reliability of MOS devices even at 400°C is excellent with an extrapolated critical field of 2.69MV/cm for a 10 year time to dielectric breakdown. The switching behavior of logic gates is also characterized between 25°C and 400°C. Using these logic gates, a fully integrated edge triggered flip-flop is build and high temperature operation is demonstrated.

Abstract: A forced-air-cooled three-phase inverter built with SiC-JFETs and -SBDs as power semi-conductor devices was designed and fabricated. The inverter can operate steadily at a rated power of 10 kW in a junction temperature range up to 200°C. Output power density of more than 20 kW/L was achieved. The design specifications, the power module fabrication process, the results of a high-temperature operating test and a continuous switching test are described in turn.

Abstract: In this paper we compare the thermal behavior of identical SiC Schottky diodes mounted in i) a standard TO220 package (TO220) with non-isolated backside applying standard soft solder and diffusion solder die attach with ii) a so called FULLPAK TO220 package (TO220FP, only diffusion soldering). Depending on the solder technique the heat transport from the junction area of the SiC Schottky diode to the heat sink or to the package backside is improved for the diodes mounted via diffusion solder. For small chips this holds even for TO220FP in comparison to TO220 with standard solder. Simulations of the vertical temperature distribution after electrically heating with a half sine wave for 10ms up to 190W show a decrease of the maximal junction temperature of the SiC Schottky diode from TJ=260 °C to TJ=180 °C if the diffusion solder is used independent from the package type.