Electric-field-limiting structure in trench-type SiC-MOSFETs

September 30, 2019 //By Julien Happich
SiC-MOSFETs
Electric Mitsubishi has developed a trench-type silicon-carbide (SiC) metal-oxide-semiconductor field-effect transistor (MOSFET) with a unique electric-field-limiting structure, improving reliability while maintaining the breakdown voltage of over 1,500V.

What’s more, the new device can achieve a world-leading specific on-resistance of 1.84 mΩ (milliohms) cm2, leading to energy savings and equipment downsizing.

SiC-MOSFETs control current flowing through the semiconductor layer between the drain and source electrodes by applying a voltage to the gate electrode. To achieve control with a small voltage, a thin gate-insulating film is required. If high voltage is applied in a trench-type power semiconductor device, a strong electric field can concentrate in the gate and can easily break the insulating film.

To correct this, the electric-field-limiting structure developed by Mitsubishi Electric protects the gate-insulating film. It consists of aluminium and nitrogen ions vertically and obliquely implanted at the bottom of the trench structure, forming an electric-field-limiting layer on the bottom surface of the trench. The electric field applied to the gate-insulating film is reduced to the level of a conventional planar power semiconductor device, thereby improving reliability while maintaining the breakdown voltage of over 1,500V.


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