Toshiba introduces low on-resistance and high reliability for on-board traction inverters

     Toshiba Electronic Components & Storage Corporation has announced the development of a new bare-chip 1200 V silicon carbide (SiC) MOSFET "X5M007E120" for in-vehicle traction inverters with an innovative structure that enables low on-resistance and high reliability. X5M007E120 Test samples are now available for customer evaluation.

     When the body diode of a typical SiC MOSFETs is energized at the bipolar during reverse conduction operation, its reliability decreases due to increased on-resistance. Toshiba SiC MOSFET alleviates the above problem by embedding SBD (Schottky barrier diode) in the MOSFET to weaken the device structure of the body diode, but if the SBD is arranged on the chip, it will reduce the plate area provided for the channel, and the plate area can not only determine the resistance of the MOSFET to work. The on-resistance of the chip can also be increased.

     The embedded SBD in the X5M007E120 is arranged in a lattice pattern, rather than the usual bar pattern, which effectively inhibits the bipolar power of the device body diode and increases the upper limit of unipolar operation to approximately twice the current area, even though it occupies the same SBD mount area. In addition, the channel density can also be increased for bar arrays, and the on-resistance per unit area is very low, about 20 to 30 percent lower. This improved performance, low on-resistance, and reliability maintained against anti-on-operation save power for inverters used for motor control, such as traction inverters.

     Reducing the on-resistance of the SiC MOSFETs results in too much current flowing through the MOSFETs during short circuits, thereby reducing short circuit durability. In addition, enhancing the conduction of the embedded SBD, improving the reliability of the reverse conduction work, will also increase the leakage current in the short circuit, which can again reduce the short circuit durability. The latest bare metal has a deep barrier structure designed to suppress excessive current of MOSFETs and leakage current of SBDS in the short-circuit state, which improves its durability while maintaining extremely high reliability against reverse conduction operation.