News: Microelectronics
29 April 2021
Imec and Aixtron demo 200mm GaN epi on AIX G5+ C for 1200V applications with breakdown over 1800V
Nanoelectronics research centre imec of Leuven, Belgium and deposition equipment maker Aixtron SE of Herzogenrath, near Aachen, Germany have demonstrated epitaxial growth of gallium nitride (GaN) buffer layers qualified for 1200V applications on 200mm QST substrates, with a hard breakdown exceeding 1800V. The manufacturability of 1200V-qualified buffer layers is reckoned to open doors to the highest-voltage GaN-based power applications such as electric vehicles (EV), previously only with feasible silicon carbide (SiC)-based technology. The result comes after qualification of Aixtron’s G5+ C fully automated metal-organic chemical vapor deposition (MOCVD) reactor at imec for integrating the optimized material epi-stack.
Wide-bandgap materials GaN and SiC have proved their value as next-generation semiconductors for power-demanding applications where silicon falls short. SiC-based technology is the most mature, but it is also more expensive. Over the years great progress has been made with GaN-based technology grown on 200mm silicon wafers, for example. At imec, qualified enhancement-mode high-electron-mobility transistors (HEMTs) and Schottky diode power devices have been demonstrated for 100V, 200V and 650V operating voltage ranges, paving the way for high-volume manufacturing applications. However, achieving operating voltages higher than 650V has been challenged by the difficulty of growing thick-enough GaN buffer layers on 200mm wafers. Therefore, SiC so far remains the semiconductor of choice for 650-1200V applications – including electric vehicles and renewable energy, for example.
For the first time, imec and Aixtron have demonstrated epitaxial growth of GaN buffer layers qualified for 1200V applications on 200mm QST (in SEMI standard thickness) substrates at 25°C and 150°C, with a hard breakdown exceeding 1800V.
Graphic: Vertical forward buffer leakage current measured on 1200V GaN-on-QST at two different temperatures: (left) 25°C and (right) 150°C. Imec’s 1200V buffer shows vertical leakage current below 1µA/mm2 at 25°C and below 10µA/mm2 at 150°C up to 1200V with a breakdown in excess of 1800V both at 25°C and 150°C, making it suitable for processing of 1200V devices.
“GaN can now become the technology of choice for a whole range of operating voltages from 20V to 1200V,” says Denis Marcon, senior business development manager at imec. “Being processable on larger wafers in high-throughput CMOS fabs, power technology based on GaN offers a significant cost advantage compared to the intrinsically expensive SiC-based technology.”
Key to achieving the high breakdown voltage is the careful engineering of the complex epitaxial material stack in combination with the use of 200mm QST substrates, executed in scope of the Imec Industry Affiliation Program (IIAP). The CMOS-fab friendly QST substrates from Qromis Inc of Santa Clara, CA, USA have a thermal expansion that closely matches the thermal expansion of the GaN/AlGaN epitaxial layers, paving the way for thicker buffer layers – and hence higher-voltage operation.
“The successful development of imec’s 1200V GaN-on-QST epi technology into Aixtron’s MOCVD reactor is a next step in our collaboration with imec,” says Aixtron’s CEO & president Dr Felix Grawert. “Earlier, after having installed Aixtron G5+ C at imec’s facilities, imec’s proprietary 200mm GaN-on-Si materials technology was qualified on our G5+ C high-volume manufacturing platform, targeting for example high-voltage power switching and RF applications and enabling our customer to achieve a rapid production ramp-up by pre-validated available epi recipes,” he adds. “With this new achievement, we will be able to jointly tap into new markets.”
Currently, lateral e-mode devices are being processed to prove device performance at 1200V, and efforts are ongoing to extend the technology towards even higher-voltage applications. Next to this, imec is also exploring 8-inch GaN-on-QST vertical GaN devices to further extend the voltage and current range of GaN-based technology.
Imec and Qromis present p-GaN HEMTs on 200mm CTE-matched substrates
