Since QST® substrate is designed to have the same coefficient of thermal expansion (CTE) as GaN, it enables suppression of warpage and cracking of the GaN epitaxial layer and resultant large-diameter, high-quality thick GaN epitaxial growth. Taking advantage of these characteristics, it is expected to be applied to power devices and RF devices (5G and beyond 5G), which have been rapidly growing in recent years, as well as in such areas as MicroLED growth for MicroLED displays.
In addition to sales of QST® substrates, Shin-Etsu Chemical will also sell GaN grown QST® substrates upon customer request. We currently have a line-up of 6" and 8" diameter substrates, and we are working on 12" diameter substrates. Since 2021, for each respective application for power devices, RF devices and LEDs, sample evaluation and device development are continuing with numerous customers in Japan and globally. Especially for power devices, continuous evaluation is underway for devices in the wide range of 650V to 1800V.
So far, Shin-Etsu Chemical has repeatedly made many improvements with regard to its QST® substrates. One example is the significant improvement in lowering defects originating from the bonding process, which has enabled the supply of high-quality QST® substrates. In addition, for the thicker GaN films that many of our customers have requested, we have promoted the provision of template substrates with optimized buffer layers, which enables our customers to realize stable epitaxial growth of more than 10 μm thickness. Furthermore, various successful results have been produced and reported on, including the achievement of thick-film GaN growth exceeding 20 μm using QST® substrates and the achievement of 1800V breakdown voltage*2 in power devices.
Moreover, Shin-Etsu Chemical and Oki Electric Industry Co., Ltd. have jointly succeeded in developing a technology to exfoliate GaN from QST® substrates and bond it to substrates made of different materials using Crystal Film Bonding (CFB)*3 technology. Until now, most GaN power devices have been lateral devices, but CFB technology takes advantage of the characteristics of QST® substrates to realize vertical power devices that can control large currents by exfoliating a thick layer of high-quality GaN from an insulating QST® substrate. To customers who manufacture GaN devices, Shin-Etsu Chemical will provide QST® substrates or GaN grown QST® substrates and Oki Electric Industry will provide its CFB technology through partnering or licensing. In this way, the two companies hope to contribute to the advancement of vertical power devices.
Based on these development results and also based on business situation inquiries from customers, Shin-Etsu Chemical will continue to increase production to meet customer demand.
Shin-Etsu Chemical will contribute to the realization of a sustainable society that can use energy efficiently by further promoting the social implementation of GaN devices that have characteristics that are absolutely essential for the future society.
Shin-Etsu Chemical will make a presentation on the progress in the development of this product at SEMICON Taiwan, which will be held in Taiwan from September 6 to 8, 2023.
*1: A QST® substrate is a composite material substrate developed by Qromis, Inc. (Head Office: Santa Clara, California; CEO Cem Basceri) exclusively for GaN growth and was licensed to Shin-Etsu Chemical in 2019. QST® is a registered trademark held by Qromis, Inc. in the United States (registration number 5277631).
*2: Please refer to the following imec release (April 2021).
https://www.imec-int.com/en/press/imec-and-aixtron-demonstrate-200-mm-gan-epitaxy-aix-g5-c-1200v-applications-breakdown-excess
*3: CFB technology is a technology to exfoliate GaN epitaxial layers from substrates and is a registered trademark of Oki Electric Industry.