Emcore receives patent on separating GaN LEDs
While die separation is typically accomplished using a scribe-and-break process, this method is not well suited to sapphire, which has a hexagonal crystal structure. The scribe will cleave well along one set of crystal planes, but makes the wafer difficult to cleave in the perpendicular direction, which does not lie along defined crystal planes. This leads to wandering during the cleaving process, reducing the usable area of the wafer and resulting in device yields of typically 70-80%.
In the new process, a laser beam passes through optical elements and masks to produce a patterned laser projection, which is then directed at the wafer surface. The laser ablates the material and cuts at least 50 µm into the substrate, well below the depth of devices and conventional scribe and break methods. According to marketing director Tom Ryan, the process produces yields of 99% for a 2-inch wafer containing 350 µm size LEDs, and typically takes 15-20 minutes for a complete wafer.
"The growing demand for LEDs and the increasing number of applications in which they are used make manufacturing efficiency vitally important," said Ryan. "By achieving typical separation yields of 99%, this new technique provides distinct advantages for LED manufacturers. These manufacturers can now make significant progress in satisfying capacity demands and expanding the potential market size for new LED applications."
Emcore says the new method has been successfully employed in a high-volume LED production facility for over a year, and will improve manufacturing times for GaN-based blue and green LEDs. The company believes the new process will also have a significant impact on the cost and manufacturability of other devices on sapphire substrates, and is currently discussing licensing the technology to a number of major LED manufacturers.
