After several years of development, Bosch is now starting volume production of power semiconductors made of silicon carbide (SiC).
“The future for silicon carbide semiconductors is bright. We want to become a global leader in the production of SiC chips for electromobility,” says Harald Kroeger, member of the Board of management of Robert Bosch GmbH. Two years ago, the supplier of technology and services had announced that it would push ahead with the development of SiC chips and enter production.
For this, Bosch has developed its own highly complex manufacturing processes, which it has been using to produce the special semiconductors since the beginning of 2021 – initially as samples for customer validation. “Our order books are full, thanks to the boom in electromobility,” Kroeger says. In the future, Bosch intends to expand its production capacity for SiC power semiconductors to a unit volume running into hundreds of millions. With this in mind, the company has already started expanding the clean-room space at its Reutlingen plant. In parallel, work is also being done on the second generation of SiC chips, which will be even more efficient and should be ready for volume production as of 2022.
Small atom, big impact
The secret behind SiC chips’ impressive performance lies in a tiny carbon atom. Introducing it into the crystalline structure of the ultra-pure silicon generally used to manufacture semiconductors gives the raw material special physical properties: for example, silicon carbide semiconductors support higher switching frequencies than pure silicon chips.
What’s more, they lose only half as much energy in the form of heat, thereby increasing the range of electric vehicles. The chips are also important for 800-volt systems, where they enable faster recharging and better performance. Since the SiC chips also emit significantly less heat, the power electronics require less in the way of costly cooling. In addition to weight, this is another way to reduce the cost of electric vehicles.
In the future, Bosch says it will supply silicon carbide power semiconductors to customers around the world – both as individual chips and installed in power electronics or complete solutions such as the e-axle. This combination of electric motor, gearbox, and power electronics achieves an efficiency of up to 96 percent thanks to the more efficient design of the overall system. This leaves more energy for the powertrain, which increases the range.
SiC market billed to grow by 30% each year
Around the world, demand for silicon carbide power semiconductors is rising. A forecast by the market research and consulting company Yole indicates that, between now and 2025, the SiC market as a whole will grow on average by 30 percent a year to over 2.5 billion dollars. At around 1.5 billion dollars, the SiC car market is expected to account for the lion’s share.
“Silicon carbide power semiconductors make particularly efficient use of energy. This material’s advantages really come to the fore in energy-intensive applications such as electromobility,” Kroeger says.
In the power electronics of EVs, silicon carbide chips ensure that drivers can drive significantly further on one battery charge – on average around 6 percent further than with their pure silicon counterparts. In order to meet steadily increasing demand for these semiconductors, an extra 1,000 square metres were added to the clean-room space at the Bosch wafer fab in Reutlingen earlier this year. Another 3,000 square meters will be added by the end of 2023.
The new space will house state-of-the-art production facilities for manufacturing silicon carbide semiconductors using processes developed in-house. To achieve this, Bosch’s semiconductor experts are building on their decades of expertise in chip manufacturing. In the future, the company plans to manufacture the semiconductors on 200-millimeter wafers.
Compared with today’s 150-millimeter wafers, this will deliver sizeable economies of scale. After all, it takes several months for a single wafer to pass through several hundred process steps in countless machines. “By producing on larger wafers, we can manufacture significantly more chips in one production run and thus supply more customers,” Kroeger says.
Bosch is not the sole automotive supplier to produce its own SiC chips. Wolfspeed, STMicroelectronics, Infineon and Onsemi make their own chips too.