An Australian-UK consortium is offering a epitaxial silicon carbide buffer layer for 300mm silicon wafers, claiming it will improve gallium nitride growth for GaN-on-Si LED fabrication.

The buffer is the result of over 10 years research at the Queensland Micro and Nanotechnology Facility (QMF) of Griffith University, and a tie-up with Gwent-based fab equipment maker SPTS Technologies.

"Fabricating GaN LEDs and power devices on large diameter silicon wafers is viewed as a path to reduce cost. However, existing buffer layers used to bridge the large thermal and lattice mismatch between silicon and GaN are costly and not completely effective for large scale production," claimed SPTS. "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, of particular concern for power devices."

Initial estimates suggest the process would add no more than $35 to mass produced wafers.

"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," said 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. We have already achieved SiC film thickness uniformities of around 1% on 300mm wafers."

"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", said SPTS CEO William Johnson. "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 optimise process and control substrate costs."