A Method for Fabricating Cavity-SOI and Its Verification Using Resonant Pressure Sensors

Area of Science:

• Materials Science
• Mechanical Engineering
• Nanotechnology

Background:

• Cavity silicon on insulator (Cavity-SOI) offers design flexibility for microelectromechanical systems (MEMS).
• Traditional MEMS fabrication faces challenges with complexity and release processes.

Purpose of the Study:

• To develop and validate a novel micromachining process for Cavity-SOI fabrication.
• To demonstrate the technical viability of Cavity-SOI for MEMS devices, specifically a resonant pressure sensor (RPS).

Main Methods:

• Integration of dry etching, wafer-level Au-Si eutectic bonding, and chemical mechanical polishing (CMP).
• Design and fabrication of a MEMS resonant pressure sensor (RPS) using the Cavity-SOI approach.
• Experimental validation of cavity formation, sealing, depth control, and sensor performance.

Main Results:

• Dry etching achieved precise cavity dimensions; Au-Si bonding ensured efficient sealing; CMP controlled cavity depth.
• Cavity-SOI enabled spontaneous resonator release, avoiding HF release issues like undercut and adhesion.
• The MEMS RPS demonstrated high sensitivity (100.695 Hz/kPa), a wide operating range (-10-60 °C, 1-120 kPa), and low error (<0.012% FS).

Conclusions:

• The proposed Cavity-SOI fabrication method streamlines MEMS production and overcomes traditional limitations.
• The successful fabrication and performance of the MEMS RPS validate the effectiveness and practicality of the Cavity-SOI approach.
• This breakthrough enables the development of advanced MEMS devices for diverse industrial applications.