Hermeticity Analysis on SiC Cavity Structure for All-SiC Piezoresistive Pressure Sensor

• Main Authors: Baohua Tian, Haiping Shang, Lihuan Zhao, Dahai Wang, Yang Liu, Weibing Wang
• Format: Article
• Language: English
• Published: MDPI AG 2021-01-01
• Series: Sensors
• Subjects: all-silicon carbide (SiC); sealed cavity structure; room temperature bonding; hermeticity; piezoresistive pressure sensor
• Online Access: https://www.mdpi.com/1424-8220/21/2/379

The hermeticity performance of the cavity structure has an impact on the long-term stability of absolute pressure sensors for high temperature applications. In this paper, a bare silicon carbide (SiC) wafer was bonded to a patterned SiC substrate with shallow grooves based on a room temperature direct bonding process to achieve a sealed cavity structure. Then the hermeticity analysis on the SiC cavity structure was performed. The microstructure observation demonstrates that the SiC wafers are tightly bonded and the cavities remain intact. Moreover, the tensile testing indicates that the tensile strength of bonding interface is ~8.01 MPa. Moreover, the quantitative analysis on the airtightness of cavity structure through leakage detection shows a helium leak rate of ~1.3 × 10⁻¹⁰ Pam³/s, which satisfies the requirement of the specification in the MIL-STD-883H. The cavity structure can also avoid an undesirable deep etching process and the problem caused by the mismatch of thermal expansion coefficients, which can be potentially further developed into an all-SiC piezoresistive pressure sensor employable for high temperature applications.