An article recently made available on Engineering delves into silicon carbide (SiC)-based pressure sensors. A comprehensive review paper titled "Pressure Sensors Based on the Third-generation Semiconductor Silicon Carbide: A Comprehensive Review" offers in-depth insights into the development and application of these sensors, which are crucial for various industries, especially those operating in extreme environments.
SiC, a third-generation wide-bandgap semiconductor, has excellent properties such as a wide bandgap, high carrier saturation drift rate, and strong chemical stability. These make it an ideal material for high-temperature pressure sensors. The global pressure sensor market is expected to grow steadily, and SiC-based sensors are attracting increasing attention due to their ability to withstand harsh conditions.
The review covers multiple aspects of SiC pressure sensors. It begins with an analysis of SiC single-crystal growth and epitaxy. The growth quality of SiC single-crystal substrates is crucial for device performance, but it faces challenges like high costs and technical barriers. Currently, methods like physical vapor transport (PVT) and liquid phase epitaxy (LPE) are used, each with its own advantages and limitations. Epitaxial layers grown on SiC substrates also play a vital role in determining sensor performance, with parameters such as doping concentration and thickness being precisely controlled.
Key technologies of SiC pressure sensors are also discussed. The piezoresistive effect of SiC is a fundamental principle for piezoresistive pressure sensors. The gauge factor (GF) of SiC varies with doping concentration and temperature. Generally, increasing the doping concentration reduces the GF value. Ohmic contacts are essential for device signal input and output. Different metals are used for n-type and p-type SiC ohmic contacts, and researchers are still exploring the formation mechanisms.
Etching of SiC is another critical technology. Due to SiC's high bonding energy and chemical inertness, etching is challenging. Wet etching and dry etching methods have their own characteristics and applications. For example, wet etching is used for defect assessment and microstructure manufacturing, while dry etching, such as reactive-ion etching (RIE) and inductively coupled plasma (ICP), offers high etching quality and precise control over structural dimensions.
Sensor packaging is equally important, especially for high-temperature applications. Leaded and leadless packaging methods have their pros and cons. Leaded packaging is well-established but has limitations in high-temperature environments, while leadless packaging, like flip-chip packaging, shows potential for miniaturization and high-temperature stability.
SiC pressure sensors have significant potential in the field of pressure sensing. However, challenges remain in areas such as sensor design, etching processes, and packaging. Future research should focus on improving sensor performance, enhancing high-temperature stability, and promoting sensor integration. This will enable SiC pressure sensors to better meet the needs of various industries in extreme environments.
The paper "Pressure Sensors Based on the Third-generation Semiconductor Silicon Carbide: A Comprehensive Review," authored by Xudong Fang, Chen Wu, Bian Tian, Libo Zhao, Xueyong Wei, Zhuangde Jiang. Full text of the open access paper: https://doi.org/10.1016/j.eng.2024.12.036 .
