Excited Caracal pounces on SiC epitaxy patent
Caracal Semiconductor, the SiC materials specialist start-up, has been awarded a US patent for its invention of an epitaxial growth technique that could increase deposition speed by a factor of ten.
Based in Ford City, PA, the company first emerged in late 2005 but, like the big cat from which it takes its name, has kept a low profile since then.
US patent 7,247,513, which was awarded to inventor Olof Kordina on July 24, details an improvement that Caracal says either eliminates or greatly reduces the phenomenon of homogenous nucleation.
By adding a dissociation-enhancer into a precursor stream containing a silicon source, silicon clusters can be dissociated in the gas phase, reads the patent text.
Using hydrogen chloride gas as the dissociation-enhancer not only improves the morphology of the film deposited, but also improves the material growth rate, the patent continues.
The result may come as a surprise to some people in the SiC field, since the highly reactive HCl would be expected to etch any material that it comes into contact with, and also to slow the growth rate.
In conventional SiC epitaxy, growth rates are typically in the order of 5-10 µm/hour, Caracal said. With the firm s new approach, that growth rate may be increased to more than 100 µm/hour with no impact on quality or doping.
If it can be scaled up and applied commercially, Caracal's technology could enable the realization of very-high-voltage power devices based on SiC.
According to Caracal, a number of companies and organizations worldwide have already verified the tremendous benefits of the approach.
"We are very excited about this patent being awarded to us in particular since it makes such a huge impact particularly for the power industry," a spokesperson from Caracal said. The technology has been developed over the past few years with funding from the Office of Naval Research (ONR) who need this technology for their next generation warships.
Caracal has also been working with the Penn State Electro-Optics Center on the development.
Plenty more detail is offered up in the patent itself, for example the advantages Caracal sees in using two separate gas flows:
"The advantage of the separate flows of the group VII-containing compound and the silicon source is that the silicon source can react and form silicon clusters. These clusters can be readily transported through the reactor, thereby likely reducing or eliminating silicon deposits on the reactor walls."
"Once dissociated, they will deposit more readily. Hence, with the split flow of the group VII-containing compound and the silicon source, a better efficiency of your input precursors may be obtained."