An All-Silicon Resonant Pressure Microsensor Based on Eutectic Bonding.

Area of Science:

• Materials Science
• Microelectromechanical Systems (MEMS)
• Sensor Technology

Background:

• Traditional resonant pressure microsensors often suffer from thermal expansion mismatches and residual stresses.
• Glass encapsulation in microsensors can lead to significant temperature-induced disturbances, affecting accuracy.
• Developing robust encapsulation methods is crucial for high-performance pressure sensing applications.

Purpose of the Study:

• To develop and characterize an all-silicon resonant pressure microsensor utilizing eutectic bonding.
• To investigate the effectiveness of silicon cap encapsulation in mitigating temperature disturbances.
• To compare the performance of the all-silicon microsensor with a glass-encapsulated counterpart.

Main Methods:

• Design and numerical simulation of an SOI wafer-based resonant pressure microsensor with an embedded pressure-sensitive film.
• Fabrication using MEMS processes, incorporating eutectic bonding to join the SOI wafer and a silicon cap for vacuum encapsulation.
• Experimental characterization of temperature disturbances, accuracy, and short-term frequency fluctuations.

Main Results:

• The all-silicon microsensor with a silicon cap exhibited significantly reduced temperature disturbances (-0.82 Hz/°C and -2.36 Hz/°C) compared to glass-encapsulated sensors.
• Accuracy improved from 0.03% FS to 0.01% FS.
• Short-term frequency fluctuations were reduced from 3.2 Hz to 1.5 Hz.

Conclusions:

• Eutectic bonding effectively eliminates thermal expansion mismatches and residual stresses in all-silicon resonant pressure microsensors.
• Silicon cap encapsulation substantially suppresses temperature disturbances, leading to enhanced sensor accuracy and stability.
• The developed all-silicon resonant pressure microsensor represents a significant advancement in high-performance pressure sensing technology.