imec develops 200-V and 650-V power devices on 200-mm GaN-on-Si wafers

Leuven, Belgium. imec has announced that it has developed 200-V and 650-V normally-off/enhancement-mode (e-mode) power devices on 200-mm GaN-on-silicon wafers, achieving a very low dynamic R_ON dispersion (below 20%) and state-of-the-art performance and reproducibility. Stress tests have also shown a good device reliability. Imec’s technology is ready for prototyping, customized low-volume production, and technology transfer.

GaN technology offers faster switching power devices with higher breakdown voltage and lower on-resistance than silicon, making it an ideal 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 silicon 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 the growth of buffers qualified for 650 V on large-diameter 200-mm wafers. This, in combination with the choice of the Si substrate thickness and doping, increased the GaN substrate yield on 200 mm to competitive levels, enabling low-cost production of GaN power devices. Also, the cleaning and dielectric deposition conditions have been optimized, and the field-plate design (a common technique for achieving performance improvement) has been extensively studied. As a result, the devices exhibit dynamic R_ON dispersion below 20% up to 650 V over the full temperature range from 25°C to 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 (200-mm/8-inch), 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, program 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 650 V—a combination that is very challenging to achieve.”