The 4- (left) and 6-inch (right) substrates. The 4-inch substrate was co-developed by Denso and Toyota Central R&D Labs.
The 4- (left) and 6-inch (right) substrates. The 4-inch substrate was co-developed by Denso and Toyota Central R&D Labs.
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Denso Corp, Toyota Central R&D Labs Inc and Showa Denko K.K. Eexhibited a 6-inch-diameter silicon carbide (SiC) substrate that they are developing in cooperation with the R&D Partnership for Future Power Electronics Technology (FUPET) at nano tech 2013.

The dislocation (defect) density of the substrate is several thousands per square centimeter, which Denso claims is 1/10 that of commercially-available SiC substrates. The three companies aim to complete the development of the 6-inch substrate that can be used for actual products such as home appliances by the end of fiscal 2014.

The exhibited 6-inch substrate was a bare wafer on which an epitaxial film had not been formed. And the "RAF growth method" was used to grow the base material for crystal growth (seed crystal).

The RAF growth method is an SiC crystal growth technology that Denso and Toyota Central R&D Labs co-developed in 2004. It reduces dislocation density by cutting out a crystal in the direction parallel to dislocation and grow crystal again.

With the dislocation density of several thousands per square centimeter, SiC-based SBDs (Schottky barrier diodes) can be manufactured with a high yield ratio, Denso said. The companies plan to further reduce the dislocation density to use the SiC substrate for SiC-based MOSFETs (metal oxide semiconductor field effect transistor), etc.

The prices of commercially-available 4-inch SiC substrates range from ¥200,000 to 500,000 (approx US$2,153-5,382). And the prices of 6-inch products, whose samples recently started to be shipped, are expected to be much higher. The three companies intend to develop a technology to mass-produce 6-inch products at low costs by increasing crystal growth speed and improving the method for cutting out a wafer.

In the past several years, SiC devices started to be employed for rail cars, air conditioners, etc.

"The automobile industry now sees SiC differently," Denso said. "It now has more opportunities to be adapted."

It seems that completed cars equipped with SiC devices will debut for technology evaluation as early as in 2015. A Denso employee said that SiC devices will be widely employed for controlling engines, etc, in about 2019 or 2020.