The article presents a novel fabrication method for cavity silicon-on-insulator (Cavity-SOI) structures, which are tailored for microelectromechanical systems (MEMS) applications. Unlike conventional SOI, Cavity-SOI incorporates pre-etched cavities in the substrate, offering enhanced design flexibility for complex MEMS architectures and reducing fabrication steps. The proposed method integrates dry etching, wafer-level gold–silicon (Au–Si) eutectic bonding at low temperature (390 °C), and chemical mechanical polishing (CMP), enabling precise control of cavity dimensions and surface smoothness while achieving vacuum packaging.
To validate the process, the authors fabricated MEMS resonant pressure sensors (RPS) using the Cavity-SOI. Key fabrication steps included deep reactive ion etching for diaphragms and resonators, anodic bonding with BF33 glass covers, and dicing and packaging of sensor chips. Characterization demonstrated highly uniform cavity formation, smooth CMP surfaces (<1 nm roughness), and strong Au–Si bonds capable of withstanding shear stresses over 1.96 × 10⁷ Pa. SEM analysis confirmed that the method eliminated undercut issues typically caused by HF release.
Performance testing of the RPS showed dual resonant frequencies with high quality factors (Q ≈ 18,143), pressure sensitivities of 51.02 Hz/kPa and −49.675 Hz/kPa for the side and central resonators, and minimal fitting error (<0.012%) over a pressure range of 1–120 kPa and a temperature range of −10 °C to 60 °C. Differential output mode was used to compensate for temperature variations. The yield of functional devices was approximately 78.8%.
In conclusion, the study demonstrates that the proposed Cavity-SOI fabrication method simplifies MEMS manufacturing, enables precise cavity customization, ensures reliable vacuum encapsulation, and effectively mitigates common release-related fabrication issues. This approach provides a scalable and versatile platform for high-performance MEMS device development across diverse applications.
OMeda (Shanghai Omedasemi Co.,Ltd) was founded in 2021 by 3 doctors with more than 10 years of experience in nanpfabrication. It currently has 15 employees and has rich experience in nanofabrication (coating, lithography, etching, two-photon printing, bonding) and other processes. We support nanofabrication of 4/6/8-inch wafers.
