Sumitomo Ups SiC Growth Speed And Quality
Sumitomo Metal Industries has unveiled a solution-growth method that it claims produces bulk SiC twice as quickly, and with fewer defects, than conventional sublimation methods.
The Japanese steel-making specialist has already extended its high-temperature material production expertise to make 6-inch diameter SiC wafers and reached growth rates over 200 µm/h.
Sumitomo has successfully produced 5 mm-thick, 2-inch diameter single crystals, and is aiming for 10 mm thickness by March 2009 to allow wafer slicing.
The method involves dipping a seed crystal into a melt that it reticently describes as “a high-temperature solution of metals such as silicon and titanium". The seed is then rotated when pulled out of the solution, in a similar manner to the Czochralski process used for making bulk silicon.
“We can improve the crystalline quality of SiC even using a low-quality seed," Kazuhito Kamei, who s responsible for Sumitomo Metal s SiC development, told compoundsemiconductor.net.
“We feel our process could be a promising alternative to physical vapor transport and chemical vapor deposition processes, which seem to still have some problems in controlling quality," he said.
Kamei says that Sumitomo is targeting the 6H, 4H and 3C crystal polytypes of SiC, with typical dislocation densities below 104 cm-2 and getting ever lower.
Sumitomo Metal has been working on a SiC solution-based crystal growth method with Japan s New Energy and Industrial Technology Development Organization (NEDO) since 2000. It first produced 2-inch diameter material in 2004 and 6-inch in 2006.
The two are working together to help reduce SiC costs for the power semiconductor market, and say the method is compatible with epitaxy layer growth.
Kamei points out Sumitomo Metal s current involvement in the power electronics market, through its subsidiary SUMCO, which was formed by the merger of its own silicon wafer business with Mitsubishi s. SUMCO is now the second biggest silicon wafer supplier in the world.
“SiC could be a promising post-silicon material in the power electronics business," Kamei predicted.