Talking about the third semiconductor (silicon carbide SiC and gallium nitride GaN)

The third generation semiconductor has obvious advantages in physical properties, extremely broad application scenarios, and bright application prospects. From the perspective of classification, SiC is suitable for medium and high voltage devices, GaN is suitable for medium and low voltage devices, and the overlapping parts of the two are automotive electronics and photovoltaics. Let’s talk about the third-generation semiconductors (silicon carbide SiC and gallium nitride GaN) from three aspects: physical characteristics, preparation cost and energy security.

1. Physical properties: SiC materials have significant advantages over Si materials. At present, silicon-based materials are mainly used in automotive-grade semiconductors. However, due to the limitation of their own performance, it is difficult to further increase the power density of silicon-based devices, and the loss of silicon-based materials is greatly increased under high switching frequency and high voltage. Compared with silicon-based semiconductor materials, the third-generation semiconductor materials represented by silicon carbide have the characteristics of high breakdown electric field, high saturation electron drift velocity, high thermal conductivity, and high radiation resistance. SiC materials have incomparable advantages over Si materials. The specific advantages are reflected in: low energy loss, small package size, high-frequency switching, high temperature resistance, and strong heat dissipation.

As a third-generation semiconductor, GaN has the advantages of a wide bandgap (3.4 eV), a strong breakdown field (3.3 MW/cm), and a high electron saturation drift velocity (2.7 * 107 cm/s). Among the previous semiconductor materials, Si is currently the main material of integrated circuits and semiconductor devices, but its narrow band gap and low breakdown voltage make it ineffective in the application of high-frequency and high-power devices. The second-generation semiconductor materials represented by GaAs have important application value in the field of microwave communication due to their high electron mobility and radiation resistance, and are the basis of current semiconductor materials for communication. However, the bandgap and breakdown voltage of GaAs are still difficult to meet the requirements of high frequency and high power devices. Compared with the previous two generations of semiconductor materials, GaN has a larger band gap and breakdown voltage, and has high chemical stability, high temperature resistance, and corrosion resistance, so it has broad applications in optoelectronic devices and high-frequency and high-power electronic devices. prospect.

Preparation cost: The price gap with traditional products continues to narrow, and the comprehensive cost advantage is obvious. Si single crystal mainly adopts the Czochralski method, and the growth rate is relatively slow. GaN mainly grows GaN thick film on sapphire substrate, which is relatively expensive. The reasons for the price drop of SiC and GaN power devices are as follows: first, the continuous release of upstream substrate production capacity, the improvement of supply capacity, the decline of substrate prices at the material end, and the reduction of device manufacturing costs; second, the trend of mass production technology stable, the yield rate increased, and the production capacity continued to expand, driving down the market price; Third, the production line specification of the device changed from 4 inches to 6 inches, the manufacturing technology was further improved, and the number of chips produced by a single wafer was greatly increased, resulting in a significant drop in cost ; Fourth, as more mass production companies join in, competition intensifies, leading to further price declines.

On the whole, according to the tracking of CASA, the prices of SiC and GaN products have dropped rapidly in recent years, falling by more than 50% compared with 2017, while the price difference between mainstream products and Si products has also continued to narrow, and has basically reached within 4 times.

Some products have been scaled down to 2x, which has hit the sweet spot. Although the cost of third-generation semiconductor substrates is relatively high, the comprehensive cost advantage is greater than that of traditional silicon substrates, and the price gap with traditional products continues to narrow. In the future, as global semiconductor manufacturers accelerate research and development and expand production, the yield rate of production lines will gradually increase, thereby improving wafer utilization and effectively reducing device costs. Taking silicon carbide as an example, due to the disadvantages of production equipment, manufacturing process, yield and cost, silicon carbide-based devices were only used in a small range in the past.

The biggest bottleneck in the commercialization of SiC power semiconductors is the high cost of substrates. At present, the international mainstream SiC substrate size is 4 inches and 6 inches, the wafer area is small, the chip cutting efficiency is low, the yield rate of single crystal substrate and epitaxy is low, resulting in high cost of SiC devices, superimposed subsequent wafer manufacturing, packaging The yield rate is low, and the current carrying capacity and gate oxide stability still need to be improved, and the overall cost of SiC devices is still at a relatively high level.

In the future, as global semiconductor manufacturers accelerate R&D and gradually increase production line yield and wafer utilization, the cost of SiC devices will be effectively reduced, and SiC will usher in rapid growth.

Energy security: SiC helps reduce energy loss by 5 times in cars. Taking the typical application scenario of the third-generation semiconductor – new energy vehicles as an example, according to the information released by Ford, compared with the new energy vehicles driven by traditional silicon chips (such as IGBT), chips made of third-generation semiconductor materials drive New energy vehicles can reduce energy loss by about 5 times. The application of GaN power devices in data centers can greatly reduce the energy consumption of data centers, helping to reduce energy waste by 30-40%. According to the official website of Yuantuo Technology, if all data centers using silicon chip devices are upgraded to gallium nitride power chip devices, the global data centers will reduce energy waste by 30-40%, which is equivalent to saving 100 megawatt hours of solar energy. and reduce 125 million tons of carbon dioxide emissions.