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SDK Achieves Very High Surface Smoothness in SiC Epitaxial Wafers

Showa Denko K.K.
December 8, 2009

—To Be Used in New Inverters for Electric Vehicles—

Showa Denko K.K. (SDK) has achieved very high smoothness (0.4 nm in roughness) all over the surface of its largest-size four-inch silicon carbide (SiC) epitaxial wafers on a commercial production basis. SiC epitaxial wafers are produced by forming a thin layer of single-crystal SiC on the surface of SiC bulk wafers. SDK started production and sale of SiC epitaxial wafers in January this year. The roughness of 0.4 nm represents a substantial improvement compared with that of conventional SiC epitaxial wafers (1-2.5 nm), and the highest level in the world.

Power devices using SiC epitaxial wafers outperform the mainstream silicon-based semiconductors, and will find applications, for example, in inverters (devices for converting direct current into alternating current) that control rotation of motors in automobiles, railcars, and industrial/home electric appliances.

To realize SiC-based inverters, Schottky barrier diode (SBD) and metal oxide semiconductor field-effect transistor (MOSFET) should be used. While SiC-SBD is already on the market, SiC-MOSFET development is still under way. MOSFET requires high surface smoothness as it uses oxide film formed on the surface of epitaxial wafers in device operation. However, conventional SiC epitaxial wafers have uneven surface (called step bunching) and it is difficult to obtain a high-quality oxide film. Thus, the newly developed SiC epitaxial wafers with very high surface smoothness will greatly contribute to early realization of SiC-MOSFET and next-generation inverters.

When compared with the mainstream silicon-based semiconductors, SiC power devices to be used in next-generation inverters can operate at high temperatures and under high-voltage heavy current. Thus, these SiC power devices will enable the production of light-weight, small-sized power-control parts for automobiles, railcars, and industrial/home electric appliances. The devices will also reduce energy loss in the process of power control, conserving energy and restricting heat generation in parts. Because of such advantages, SiC-based inverters are expected to be used in electric vehicles and hybrid cars, contributing to reductions in CO2 emissions.

SDK will accelerate the development of SiC epitaxial wafers with larger diameter, lower deficiency and higher uniformity, while further reducing production costs. Thus, SDK intends to contribute to full-scale commercialization of heavy-current high-voltage SiC epitaxial wafers and establish production/marketing setup by 2012, when such full-scale commercialization is expected to start.


(1) Conceptual drawings of SBD and MOSFET based on SiC epitaxial wafers

(2) Appearance of SiC epitaxial wafers

(From left, two, three, and four inches in diameter)

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