The Queensland Micro and Nanotechnology Facility (QMF) of Griffith University in Brisbane, Australia and its industry partner, plasma etch, deposition and thermal processing equipment maker SPTS Technologies Ltd of Newport, Wales, UK, have announced the epitaxial growth of 3C silicon carbide (SiC) films on 300mm silicon wafers. The achievement is the result of over 10 years of research at QMF on low-temperature SiC deposition on silicon and the joint development by QMF and SPTS of a commercial reactor to extend the epitaxial growth process to commercial-scale production of SiC-coated silicon wafers.
The ultimate target of the joint project is to provide a cost-effective buffer material to enable the fabrication of gallium nitride (GaN) devices on silicon substrates. Fabricating GaN light-emitting diodes (LEDs) and power devices on large-diameter silicon wafers is viewed as a path to improve performance and reduce cost, hence increasing commercial acceptance of these devices. However, existing buffer layers used to bridge the large thermal and lattice mismatches between silicon and GaN are costly and not completely effective for large-scale production.
A 3C-SiC film provides an effective buffer layer lattice-matched for GaN growth on silicon, as well as an impervious barrier to prevent silicon from diffusing into GaN, which is of particular concern for power devices. Initial estimates are that the new SiC-on-silicon coating process in volume production would add no more than $25-35 to the cost of a silicon wafer, increasing the appeal of silicon as a substrate for LEDs and GaN power devices.
“We believe we are the first in the world to grow 3C-SiC epitaxially on 300mm silicon wafers, which means following the same crystal structure as the silicon crystal substrate,” says Alan Iacopi, QMF director of operations. “The reactor development project with SPTS has allowed the QMF R&D process to be extended from small wafers up to 300mm wafers with semiconductor industry specifications; in fact, we have already achieved SiC film thickness uniformities of around 1% on 300mm wafers using the new reactor,” he adds.
“We see the QMF SiC technology as a potential breakthrough in reducing the cost of LEDs and improving the performance of GaN power devices,” says SPTS’ president & CEO William Johnson. “Based on our extensive background in vertical furnace technology, the new reactor has been designed for high-temperature vacuum processing of batch loads of 150mm to 300mm wafers, with process automation suitable for commercial application. There are a number of buffer and template wafer suppliers offering alternative solutions; however, we see a strong business case for device manufacturers adopting the QMF/SPTS SiC solution to optimize process and control substrate costs,” he adds.
“The Griffith University and SPTS partnership has far-reaching implications in terms of demonstrating how Australian research entities (like QMF) can collaborate with international industry to advance frontier technologies,” says Iacopi. “We have all the ingredients to develop a high-tech economy in Queensland, including technically leading Universities, the Australian National Fabrication Facility infrastructure, entrepreneurial spirit, and start-up company investment support.”
