Cree expands "zero-micropipe" SiC to 4 inches
LED maker Cree has increased the size of “zero-micropipe” (ZMP) SiC substrates that its materials business can produce to 4 inches, although it does not expect a full commercial release of the substrates until late 2008.
Cengiz Balkas, vice president and general manager of materials at the Durham, North Carolina company, emphasized that although the production of the highest quality material was important to Cree's strategy, its existing 4-inch SiC wafers were sufficient for current applications.
“If there is a big pull in terms of our customer's demands for efficiency that require ZMP then we'll go into production, but the current product is very good,” Balkas said.
“The n-type class of material is conducting and directed towards SiC-based power electronic applications, we expect that initial use will be in SiC-Schottky [diode] applications.”
Balkas said that the company's range of semi-insulating SiC wafers, which are used in radio frequency and MESFET applications, would also move to 4-inch ZMP.
SiC, commonly used as a substrate for the growth of GaN chips, often contains crystalline defects known as micropipes which can affect device performance and lower the usable yield per wafer.
Cree has previously been able to provide 3-inch ZMP wafers, but the move to 4-inch wafers will ultimately lead to much higher-volume manufacturing, almost doubling the wafer area.
Balkas told compoundsemiconductor.net that decreasing the micropipe density to zero whilst maintaining crystal quality at the 4-inch diameter presented a significant challenge.
Although the company sells SiC wafers as products in their own right, they are also important to Cree as the basis for many of its own chip products.
The US Army and DARPA have helped fund the ZMP development, building on the existing collaboration with the US military in which Cree makes MMICs based on SiC substrates for next-generation radar applications (see related stories).
