Fabrication of Buried Microchannels with Almost Circular Cross-Section Using HNA Wet Etching

Area of Science:

• Microfluidics
• Materials Science
• Sensor Technology

Background:

• Fabricating suspended microfluidic channels presents challenges in achieving large dimensions and integrated functionalities.
• Existing methods often lack the selectivity required for precise material removal and structural release.

Purpose of the Study:

• To present a novel fabrication process for large, suspended microfluidic channels.
• To demonstrate the integration of metal electrodes for actuation and readout within the microfluidic device.
• To showcase a potential application of the fabricated channels in a micro-Coriolis sensor.

Main Methods:

• Utilizes Buried Channel Technology with a selective etchant mixture (HF, HNO3, water) for precise silicon removal.
• Employs a silicon-rich silicon nitride mask material for high etch selectivity.
• Integrates metal electrodes during the fabrication process for device functionality.

Main Results:

• Successfully fabricated large, suspended microfluidic channels with near-circular cross-sections (up to 300 μm diameter).
• Achieved a channel wall thickness of 1.5 μm.
• Demonstrated the fabrication of a micro-Coriolis mass-flow and density sensor using the developed process.

Conclusions:

• The novel fabrication process enables the creation of large, suspended microfluidic channels with integrated electrodes.
• The high selectivity of the etchant and mask material is crucial for successful channel release and device fabrication.
• The process is suitable for applications requiring microfluidic structures with vibrational movement, such as Coriolis sensors.