Toyota Denso makes a big push into silicon carbide

Source: Content from Semiconductor Industry Observation, thank you

Last December, Denso announced that as part of its efforts to achieve a low-carbon society, its latest model of boost power module equipped with high-quality silicon carbide (SiC) power semiconductors has begun mass production and will be used in Toyota's new Mirai model, which will be launched on December 9, 2020.

In the introduction, DENSO said that the company developed REVOSIC technology to apply SiC power semiconductors (diodes and transistors) to automotive applications. They pointed out that silicon carbide is a semiconductor material with superior performance in high temperature, high frequency and high voltage environments compared to traditional silicon (Si). Therefore, the use of SiC in key devices to significantly reduce the power loss, size and weight of the system and accelerate electrification has attracted widespread attention.

In 2014, DENSO introduced a SiC transistor for non-automotive applications and commercialized it for use in audio products. DENSO continued its research into automotive applications, and in 2018, Toyota used automotive SiC diodes in its Sora fuel cell bus.

Now, DENSO has developed a new automotive SiC transistor, marking the first time DENSO has used SiC for automotive diodes and transistors. The newly developed SiC transistor provides high reliability and high performance in the automotive environment, which poses a challenge to semiconductors, thanks to DENSO's unique structure and processing technology, applying trench gate MOSFET. The new boost power module equipped with SiC power semiconductors (diodes, transistors) is about 30% smaller and has a power loss of about 70% compared to previous products equipped with Si power semiconductors, which helps to achieve miniaturization. Boost power module, improve vehicle fuel efficiency.

DENSO said it will continue to focus on the research and development of REVOSIC technology and expand its application to electric vehicles, including hybrid vehicles and pure electric vehicles, to help build a low-carbon society.

Recently, DENSO pointed out in a press release that power semiconductors are like muscles in the human body. It moves components such as inverters and motors (limbs) according to commands from the ECU (brain). Typical power semiconductors used in automotive products are made of silicon (Si). In contrast, silicon carbide has excellent performance in high temperature, high frequency and high voltage environments, which helps to significantly reduce the power loss, size and weight of the inverter. Therefore, SiC devices have attracted attention for their accelerated vehicle electrification.

Denso pointed out that compared with traditional products using silicon power semiconductors, the boost power module using the company's silicon carbide power semiconductors is about 30% smaller and the power loss is reduced by 70%. This can make the product smaller and improve the fuel efficiency of the vehicle.

Denso engineers also said that compared with silicon, silicon carbide has low resistance, so current flows more easily. Due to this characteristic, a prototype SiC device was damaged by a sudden large current surge. To this end, multiple departments of Denso cooperated to discuss how to prevent damage to devices on the market while fully utilizing the low-loss performance of SiC, and solved the problem with an idea that our department could not come up with alone: ​​using a special driver IC to cut off the current at high speed.

Silicon carbide patents: Denso ranks fifth

According to Nikkei, Japanese and American companies have monopolized the top five patents related to silicon carbide (SiC), a new generation semiconductor material. According to statistics from Patent Result, a Japanese company engaged in patent analysis, Cree, an American company involved in silicon carbide semiconductor substrates, ranks first, and Japanese companies such as Rohm and Sumitomo Electric Industries rank second to fifth.

Based on the data of US patents published as of July 29, the scores were calculated by quantity and attention. Silicon carbide is used as a substitute for existing silicon semiconductor substrate materials, contributing to improved performance and energy saving of power semiconductors. The application scope of silicon carbide is expanding in areas such as inverters for pure electric vehicles (EVs) and photovoltaic power generation systems. Demand is expected to expand under the decarbonized society.

The analysis of Patent Results shows that Cree, ranked first, has advantages in patents for silicon carbide substrates and crystallization. Rohm, ranked second, and Denso, ranked fifth, have advantages in reducing power loss, Sumitomo Electric, ranked third, is stronger in the crystal structure of silicon carbide, and Mitsubishi Electric, ranked fourth, has advantages in semiconductor device structure.

Denso has even bigger goals

In 2019, Toyota and Denso jointly announced the establishment of a new joint venture. The new company will focus on the development of next-generation automotive semiconductor technology. They have set their sights on power semiconductor gallium oxide and diamond that can challenge SiC (silicon carbide) and GaN (gallium nitride).

Through in-depth research on the basic structure and processing technology of the products, the new joint venture will focus on the development of advanced forward-looking technologies for electronic components such as power modules for electric vehicles or peripheral monitoring sensors for autonomous vehicles.

As one of the few automakers in the world that can produce IGBTs on its own, Toyota has in-depth cooperation with Fuji Electric, Mitsubishi Electric, and Denso. Denso has invested in Infineon and cooperated with FLOSFIA, a technology startup founded by Kyoto University, to strengthen the development and application of automotive semiconductor products. They are all investing in and developing a new generation of power semiconductor devices to reduce and lower the cost and size of power modules used in electric vehicles.