Mitsubishi Electric Corporation
The University of Tokyo
No. 3233

Mitsubishi Electric and the University of Tokyo Reveal New Mechanism forEnhancing Reliability of SiC Power Semiconductor Devices
TOKYO, December 4, 2018 – Mitsubishi Electric Corporation (TOKYO: 6503) and the University of Tokyoannounced today what they believe to be an all-new mechanism for enhancing the reliability of silicon carbide(SiC) power semiconductor devices in power electronics systems. The new mechanism was realized as a resultof confirming that sulfur beneath the interface of gate oxide and SiC captures some of the electrons conducting
in the device’s current path, which increases the threshold voltage without changing the device’s on-resistance.
The mechanism is expected to lead to more reliable power electronics equipment offering superior tolerance
to electro-magnetic noise, which is known to cause system malfunctions.
The research achievement was initially announced at The International Electron Devices Meeting (IEDM2018)
in San Francisco, California on December 3 (PST). Going forward, Mitsubishi Electric will continue refining
the design and specifications of its SiC metal-oxide-semiconductor field-effect transistor (SiC MOSFET) tofurther enhance the reliability of SiC power semiconductor devices.

Fig.2 Relationship between SiC power
semiconductor device’s current and voltage

Fig.1 Effects of sulfur beneath the gate oxide/SiC interface

In their research, Mitsubishi Electric handled the design and fabrication of the SiC power semiconductor
devices and analysis of sulfur’s capture of electrons in the current path, while the University of Tokyo handled
measurement of electron scattering.
Until now, it had been assumed that compared to conventional nitrogen or phosphorus, sulfur is not a suitableelement to supply electrons for current conduction in SiC power semiconductor devices. Mitsubishi Electricand the University of Tokyo, however, focused on a different property of sulfur, namely, that sulfur in SiC
inherently tends to capture electrons. Confirmation of this property was the basis of developing the newmechanism for SiC power semiconductor devices.
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A proper quantity and distribution of sulfur in the mechanism’s SiC (Fig. 1, on right) blocks electrons near theinterface to a certain extent and thereby increases threshold voltage without impacting on-resistance. A suitable
atom offering such an electrical property has been strongly sought to realize devices that are not prone tomalfunctioning due to the effects of external electro-magnetic noise. The new mechanism is more reliable inthis regard than conventional mechanisms (Fig. 2) and still retains low on-resistance.
Background
Power equipment used in home electronics, industrial machinery, trains, etc. are designed for maximized
efficiency and minimized size. Mitsubishi Electric is accelerating the use of SiC power semiconductor devices
in power semiconductor modules, which are key components in power equipment. SiC power semiconductor
devices offer lower on-resistance than conventional silicon power semiconductor devices, but lowering theiron-resistance too far reduces threshold voltage and weakens tolerance to electro-magnetic noise from thepower electronics system. To overcome this problem, Mitsubishi Electric pursued the development of areliable SiC power semiconductor device that is tolerant to electro-magnetic noise.
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www.MitsubishiElectric.com/company/rd/###About Mitsubishi Electric Corporation
With nearly 100 years of experience in providing reliable, high-quality products, Mitsubishi Electric
Corporation (TOKYO: 6503) is a recognized world leader in the manufacture, marketing and sales of electricaland electronic equipment used in information processing and communications, space development and satellite
communications, consumer electronics, industrial technology, energy, transportation and building equipment.
Embracing the spirit of its corporate statement, Changes for the Better, and its environmental statement, EcoChanges, Mitsubishi Electric endeavors to be a global, leading green company, enriching society withtechnology. The company recorded consolidated group sales of 4,444.4 billion yen (in accordance with IFRS;
US$ 41.9 billion*) in the fiscal year ended March 31, 2018. For more information visit:
www.MitsubishiElectric.com*At an exchange rate of 106 yen to the US dollar, the rate given by the Tokyo Foreign Exchange Market on
March 31, 20182/2