German foundry X-Fab Silicon Foundries is moving its fab in Lubbock, Texas, entirely to silicon carbide (SiC), and says it is the first to add an in-house epitaxial process to improve yields.
The automotive-qualified fab has a capacity of 26,000 6in wafers per year that it expects to be moved over to SiC wafers from silicon. The fab also has the ability to add one or two layers of epitaxy on top of these SiC wafers depending on the application to improve the yield.
“SiC is a unique, discrete product and there are two or three different ‘care abouts’ in the performance: breakdown voltage, leakage of a diode and forward voltage drop,” said Chris Toelle, SiC business director. “All of our customers will be defining a certain application and that will determine the sweet spot and then what we will be able to do is tune the parametric sweet spots and at the same time driving yield,” he said. “If you use a standard epi wafer on different projects you don’t necessarily hit the sweet spot for either and you might see lower yield.”
The epi process has been added for SiC wafers to improve the quality and yield. “SiC substrate production at 6in is still in its infancy,” said Ed Pascasio, CFO at X-FAB Texas
“You need to start with a good substrate so having access to those substrate suppliers and assess the market on where those suppliers are on their quality is critical," he said. "The SiC wafers have many, many defects so you have to put the epi on top of it to provide a higher quality layer. You still have to start with a good quality wafer substrate to get the yield.”