When Will the Third Generation of Semiconductors Move Towards Large Silicon Wafers?

With the rapid development of new energy vehicles, power grids, 5G communication and other fields, the third generation semiconductor represented by SiC and GaN gradually reveals its role as a substitute for silicon-based semiconductor by its advantages in high pressure, high temperature and high frequency applications, and is considered to be an important development direction of the semiconductor industry.

So far, silicon wafers are transitioning from 8 inches to 12 inches. Larger wafers mean more chips can be made on a single wafer, less waste on the edge of the wafer, and less cost per chip. The third generation of semiconductors is no exception, and all are making big strides towards larger wafers.

SiC, Into the Age of Eight Inches

SiC has the characteristics of high breakdown electric field, high saturation electron velocity, high thermal conductivity, high electron density and high mobility. It is a good semiconductor material, and has been widely used in automotive electronics, industrial semiconductor and other fields.

Domestic enterprises in SiC substrate to 4 inches, at the same time, Shandong Tianyue, Tianke Heda, Hebei Tongguang, Zhongke Energy saving, Lu Xiao technology and other manufacturers have completed the research and development of 6 inches substrate; China Electronics Equipment has successfully developed a 6 inch half insulated substrate, forming an independent technology system on SiC single crystal substrate technology. Shanxi Shuoke, Jingsheng, Tianke Heda and other companies have also made achievements in 8 inch SiC substrate technology.

In the world, Wolfspeed, ROM, stmicroelectronics, Onsen, II-VI, Soitec and other enterprises have successfully developed 8 inch SiC substrate.

According to the forecast of China Wide Gap Power Semiconductor and Application Industry Alliance, it is estimated that the domestic 4-inch SiC wafer market will gradually decrease from 100,000 pieces to 50,000 pieces in 2020-2025, and the 6-inch wafer market will grow from 80,000 pieces to 200,000 pieces. From 2025 to 2030, 4-inch wafers will gradually withdraw from the market, and 6-inch wafers will increase to 400,000 wafers.

It is worth noting that while the arrival of the 8-inch SiC has certainly brought some changes to the industry, the majority of SiC product lines are currently 6-inch production lines.

Although there is little difference between 8 inch SiC and 6 inch SiC in ion implantation, thin film deposition, medium etching, metallization and other aspects of power semiconductor manufacturing, there are many manufacturing difficulties in 8 inch sic substrate growth, substrate cutting processing, oxidation process and other aspects. In terms of substrate growth, expanding the diameter to 8 inches increases the difficulty of substrate growth exponentially. In terms of substrate cutting processing, the larger the size of substrate cutting stress and warping problems are more significant. Oxidation process has always been the core difficulty in silicon carbide process. 8 inch and 6 inch have different requirements on the control of airflow and temperature field, so the process needs to be developed independently. At present, the leading manufacturers are also cooperating with the upstream and downstream technology manufacturers in the supply chain to develop their own manufacturing equipment and production process. As a result, upgrading SiC wafers to 8 inches also requires upgrading and replacing manufacturing equipment and the overall support ecosystem.

According to Wolfspeed's data, the number of bare chips (chips) on an 8-inch wafer with an area of 32mm2 increased by nearly 90% compared to a 6-inch wafer, while the percentage of bare chips on the edge decreased from 14% to 7%, meaning that the utilization of 8-inch wafers increased by 7% compared to a 6-inch wafer. Therefore, the development of larger wafers is the inevitable trend of increasing demand. It's just going to take a while for the 6-inch to 8-inch transition relative to the 4-inch to 6-inch milestone. The 6-inch production line will be dominant for some time to come.

GaN, Six Inches is Accelerating

GaN has the characteristics of high pressure resistance, high temperature resistance and low energy loss, and has different emphasis on function with SiC. SiC focuses on high voltage and GaN on high frequency. However, GaN is expensive, difficult to etch, has been slower to industrialise than SiC, and currently has a small market of less than 1%, with wafers transitioning from 4 inches to 6 inches.

The domestic commercial GaN substrate size is mainly 2 inches, 4 inches to achieve small batch shipment, it is expected to complete the mass production of 6 inches substrate and enter the market before 2025. Major enterprises include Suzhou Nawei and Dongguan Zhong Gallium companies.

International GaN single crystal substrate suppliers include Sumitomo Electric, Kogawa Machinery, Mitsubishi Chemical, Kyma of the United States, Lumilog of France and other companies. Japan is the world's largest GaN wafer production place, accounting for more than 90% of the market share. The mainstream products in mass production are 2 inch, 4 inch and 6 inch GaN single crystal substrates. Several manufacturers have announced the completion of research and development, and some of them have realized mass production of 4 inch GAN single crystal substrates.

The common substrates of GaN devices are silicon and silicon carbide. Silicon carbide GaN RF devices have the advantages of high thermal conductivity and high power RF output, and are suitable for 5G base stations, satellites, radar and other fields. Silicon - based GaN power devices are mainly used in the field of power electronic devices. GaN devices based on GaN substrate, although in each performance index is in the leading level, but the substrate price is too high.

The upstream raw materials of GaN industry chain include GaN substrate and GaN epitaxial sheet. The cost of raw materials is high, and the import dependence is serious. The localization rate is about 10%. In the field of substrates, GaN substrates have serious technical difficulties. A 2-inch piece of GaN substrate can cost up to $5,000 in the international market, and one piece is difficult to find. So silicon - and sic - based GaN devices will be first commercially available.

GaN is widely used. As a key core device supporting the construction of "new infrastructure", its downstream application is targeted at 5G base stations, ultra-high voltage, new energy charging piles, intercity high-speed railways and other major fields in "new infrastructure". In addition, the high-efficiency electric energy conversion characteristics of GaN can help realize the efficient conversion of electric energy in photovoltaic, wind power (electric energy production), DC UHV power transmission (electric energy transmission), new energy vehicles, industrial power supply, locomotive traction, consumer power supply (electric energy use) and other fields, and help achieve the goal of "carbon peak, carbon neutrality". The global GaN component Market is expected to grow to $42.3 billion by 2026, with a compound annual growth rate of 13.5%, according to estimates by Market and Market, Yole et al.

At present, silicon is still the mainstream semiconductor material due to the influence of preparation technology, subsequent processing and raw material source. However, as the demand for end applications surges, the size of SiC and GaN wafers will be upgraded to 8 inches. Currently SiC and GaN wafers are mainly limited to 4-6 inches, it is believed that the head supplier's efforts in 8-inch wafers will lead to the increase of 8-inch wide band-gap power semiconductor wafers. The trend toward 8 "wafers for SiC and GaN will continue in the next few years.