News: Microelectronics
17 November 2025
imec achieves record GaN breakdown exceeding 650V on Shin-Etsu Chemical’s 300mm QST substrate
Tokyo-based Shin-Etsu Chemical Co Ltd says that its QST substrate has been adopted for the 300mm gallium nitride (GaN) power device development program at nanoelectronics research center imec of Leuven, Belgium, where sample evaluation is in progress. In the evaluation, a 5µm-thick high-electron-mobility transistor (HEMT) device achieved a record breakdown voltage, for a 300mm QST substrate, of more than 650V.
Dedicated to the growth of GaN, the QST (Qromis Substrate Technology) substrate was developed by QROMIS Inc of Santa Clara, CA, USA and licensed to Shin-Etsu Chemical in 2019. Shin-Etsu Chemical has since manufactured 150mm and 200mm QST substrates, as well as GaN-on-QST epitaxial substrates of various diameters. In September 2024, it started providing 300mm QST samples in a joint initiative with QROMIS.
Shin-Etsu Chemical and QROMIS have established a specific partnership to provide 300mm QST substrates for imec’s 300mm CMOS fab. imec’s 300mm GaN power device development program was officially launched in October, announcing its plan to develop a GaN power device using 300mm QST. imec’s 650V-rated product is to be followed by a variant with a 1200V+ withstand voltage, targeting AI data-center, industrial and automobile applications.
The initial evaluation results showed that imec has fabricated a 5µm-thick high-voltage GaN HEMT structure on Shin-Etsu Chemical’s 300mm QST substrate in compliance with the SEMI standards, using a Hyperion metal-organic chemical vapor deposition (MOCVD) system from Aixtron SE of Herzogenrath, near Aachen, Germany. This achieved a record breakdown voltage of over 800V, significantly exceeding 650V on substrates compliant with SEMI standards, demonstrating excellent in-plane uniformity. These results are said to demonstrate that the QST substrate, whose thermal expansion coefficient is matched to GaN, can stably deliver excellent GaN crystal growth performance even at large diameters.
Because imec’s existing silicon wafer production line can be used for GaN, increasing the substrate diameter is expected to reduce production costs. However, GaN growth on silicon wafers suffers from increasingly poor production yields at larger diameters due to issues such as wafer warpage, preventing practical mass production. The 300mm QST substrate is said to solve this issue by enabling the epitaxial growth of thick-film 300mm GaN for high-voltage applications without warping or cracks — previously unattainable on silicon wafer substrates — thus significantly reducing device costs. To date, Shin-Etsu Chemical has been enhancing facilities for 150mm and 200mm QST substrates and is currently working toward the mass production of 300mm QST substrates.
The QST substrates are currently being evaluated by many Japanese and international customers for applications such as power devices, high-frequency devices, and LEDs. They are in the development phase for practical applications to address the recently increasing interest in AI data-center power supplies.
Shin-Etsu Chemical to develop QST substrate for 300mm GaN
Shin-Etsu Chemical launches QST substrates for GaN power device growth
