The Japan-based Toshiba Electronic Devices & Storage Corp (TDSC), which was spun off from Toshiba Corp in 2017, presented research on the development of a silicon carbide (SiC) metal-oxide-semiconductor field-effect transistor (MOSFET) that arranges embedded Schottky barrier diodes (SBD) in a check pattern (check-pattern embedded SBD) to realise both low on-resistance and high reliability, at the 68th annual IEEE International According to Toshiba, the design achieves a 20% reduction in on-resistance (RonA) compared to its current SiC MOSFET, without sacrificing reliability. Due to its ability to offer greater voltages and lower losses than silicon, silicon carbide is frequently regarded as the next-generation material for power devices. SiC is currently mostly used in railway inverters, but in the future, it may also find usage in industrial equipment downsizing and vehicle electrification. Bipolar conduction in the body diode during reverse operation of SiC MOSFETs is damaging because it reduces on-resistance, thus this issue must first be resolved.
To deactivate body diodes, Toshiba Electronic Devices & Storage Corp devised a device construction that embeds SBDs within the MOSFET. However, it discovered that doing so reduces channel density and raises RonA. A new embedded SBD structure has finally resolved this trade-off, and Toshiba has confirmed that it significantly enhances performance properties. By using a check-pattern SBD distribution, Toshiba has reduced conduction loss in its SBD-embedded SiC MOSFET and obtained good diode conductivity. According to analysis of the on-side current characteristics of 1.2kV-class embedded SBD MOSFETs with the optimised design, using the check design to place the embedded SBDs close to the body diodes effectively limits bipolar conduction of the parasitic diodes, while the unipolar current limit of reverse conduction is double that realised by the existing striped SBD pattern design for the same SBD area consumption. At 2.7mOhm/cm2, RonA was discovered to be around 20% less dense. SiC MOSFETs must undergo this verified trade-off improvement before being employed in inverters for motor-drive applications. Toshiba is still conducting assessments to enhance dynamic features and dependability as well as to create appealing, high-performance power semiconductors that reduce carbon emissions.
