Research and innovation hub in nano-electronics and digital technology, imec, has announced that it has developed 200 and 650V normally-off/enhancement mode (e-mode) on 200mm/8" GaN-on-Silicon wafers, achieving a very low dynamic Ron dispersion (below 20%) and performance and reproducibility. Stress tests have also shown a good device reliability. Imec’s technology is ready for prototyping, customised low-volume production as well as for technology transfer.
GaN technology offers faster switching power devices with higher breakdown voltage and lower on-resistance than silicon (Si), making it a suitable material for advanced power electronic components. Imec’s GaN-on-Si device technology is Au-free and compatible with the wafer handling and contamination requirements for processing in a Si fab. A key component of the GaN device structure is the buffer layer, which is required to accommodate the large difference in lattice parameters and thermal expansion coefficient between the AlGaN/GaN materials system and the Si substrate. Imec achieved a breakthrough development in the buffer design (patent pending), allowing to grow buffers qualified for 650V on large diameter 200mm wafers.
This, in combination with the choice of the Si substrate thickness and doping increased the GaN substrate yield on 200mm to competitive levels, enabling low-cost production of GaN power devices. Also, the cleaning and dielectric deposition conditions have been optimised, and the field plate design (a common technique for achieving performance improvement) has been extensively studied. As a result, the devices exhibit dynamic Ron dispersion below 20% up till 650 Volt over the full temperature range from 25-150°C. This means that there is almost no change in the transistor on-state after switching from the off-state, a challenge typical for GaN technology.
“Having pioneered the development of GaN-on-Si power device technology on large diameter substrates (200mm/8"), imec now offers companies access to its normally-off/e-mode GaN power device technology through prototyping, low-volume manufacturing as well as via a full technology transfer” stated Stefaan Decoutere, Programme Director for GaN technology at imec. “Next to enhancement mode power device switches, imec also provides lateral Schottky diodes for power switching applications. Based on imec’s proprietary device architecture, the diode combines low turn-on voltage with low leakage current, up to 650V – a combination that is very challenging to achieve.”