Silicon carbide pressure sensor Aerospace and e-mobility: High-temperature sensor up to 600 °C

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Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration IZM

GGB Heilbronn GmbH

Researchers have developed a special high-temperature sensor made from silicon carbide. This sensor is intended not only for monitoring temperatures in combustion chambers but is also expected to be used in e-mobility in the future.

Conventional sensors fail at an ambient temperature of 300 °C. Researchers at Fraunhofer IZM have developed a sensor that operates safely even at twice that temperature. Through precise etching processes, they made silicon carbide usable for constructing a robust sensor. By measuring pressure in extremely harsh environments, combustion processes in aircraft turbines can be controlled, thereby reducing kerosene consumption.

Since the development of turbine steel engines in the mid-20th century, high-performance and thrust objects have been airborne. The working principle: High thrust is generated using a gas turbine and the recoil effect of air and exhaust flow, propelling the aircraft. What is not visible from the outside: Due to the strong compression of the ingested air, there is enormous pressure in the aircraft turbine, and the temperatures rise to up to 600 °C even upon entering the combustion chamber.

In space applications, the environment is even harsher. To ensure safety in aerospace and to control conditions during use, sensors are deployed. However, they must meet special requirements: In addition to accuracy and sensitivity, they must be reliable and withstand extremely corrosive environmental conditions.

Sensors made from silicon carbide

Researchers at the Fraunhofer IZM in Berlin have developed and constructed a high-temperature sensor specifically designed for harsh environmental conditions. Silicon carbide (SiC) is used, as the material is well-suited for constructing pressure sensors in terms of robustness. Conventional silicon sensors are unimaginable for such applications, as they reach their limit at 150°C.

Sensors based on so-called SOI technology (Silicon on Insulator) perform better, but even here, at temperatures above 400 °C in combination with mechanical stress, plastic deformation begins, adversely affecting measurement accuracy.

Robust and thermally stable up to 600 °C

Building the new generation of high-temperature sensors on SiC offers clear advantages: the material is extremely robust, thermally stable, and minimally reactive to chemical influences. Additionally, the material's wide bandwidth allows use at temperatures up to 600 °C. However, "Silicon carbide is both a curse and a blessing: the material's unique strength and durability are promising for electronic components. But these very properties also make it extremely difficult to process the SiC," says scientist Piotr Mackowiak from Fraunhofer IZM.

The main challenge for the developers was to construct a tiny, stable base structure on a thin membrane in a semiconductor process. To achieve this, they used a dual, rapid etching process. This etches the silicon carbide at a rate of four micrometers per minute, which is eight times the usual rates and thus interesting for high-volume manufacturing throughput.

Aerospace and e-mobility

With the high-temperature sensor, the ratio of the air-fuel mixture can be adjusted and combustion optimized. Small design changes allow the measured variables to be varied, making the sensor usable not only in aerospace but also in e-mobility or for measurements in deep drilling.