Gallium nitride (GaN) offers a number of well-documented advantageous properties, such as very good electron mobility, higher breakdown voltage, and very capable thermal conductivity. These characteristics make it particularly attractive for power and radio frequency (RF) devices, which need high-switching efficiencies. Unsurprisingly, it’s now making strong inroads in the electronics industry.
However, just as these operational advantages are well documented, so too is a well-known disadvantage: high manufacturing costs. Imec, the nanoelectronics research centre, says that GaN-based power devices are too expensive for large volume manufacturing because they’re fabricated on small diameter wafers using non-standard production processes.
Consequently, a research program implemented by Imec is concentrating on the development of GaN-on-silicon (Si) technology on 200mm wafers. Imec believes it will not only help reduce the cost of GaN, but also improve performance.
Imec says it’s achieved significant technical advances thanks to the combined efforts of leading integrated device manufacturers (IDMs), foundries, compound semiconductor companies, equipment suppliers, and substrate suppliers. Power semiconductor specialist ON Semiconductor is the latest to join the program.
In fact, the research program has already successfully produced 200mm GaN-on-Si wafers (see the figure), bringing processing within reach for standard high-productivity 200mm fabs. Moreover, Imec developed a fabrication process compatible with standard CMOS processes and tools, which has been recognised for some time now as the method for reducing GaN-related manufacturing costs.
So, is all of this GaN developmental effort worth it? Will the electronics industry in general benefit financially? Yole Développement, a market research company, says that it will, predicting a $500 million market for GaN products in 2016.
However, a number of alternative substrates are being examined, including GaN-on-sapphire, GaN-on-SiC, GaN-on-GaN, and GaN-on-AlN. Yole believes GaN-on-Si will likely dominate production—6-in.wafers topped with 7-micron-thick GaN epi are already out there. Similar 200mm-diameter wafers are under qualification, and Yole says their availability will likely make this technology the economic choice.