A Composite-Type MEMS Pirani Gauge for Wide Range and High Accuracy

Area of Science:

• Microelectromechanical Systems (MEMS)
• Vacuum Technology
• Sensor Design

Background:

• Accurate vacuum level detection is crucial for encapsulated microcavities.
• Existing Pirani gauges have limitations in measurement range and accuracy.
• There is a need for integrated vacuum sensors in micro-devices.

Purpose of the Study:

• To design and fabricate a composite-type MEMS Pirani gauge for wide-range and high-accuracy vacuum detection.
• To extend both the lower and upper measurable limits of pressure.
• To enable integration with other MEMS devices for in-situ monitoring.

Main Methods:

• A series connection of two MEMS Pirani gauges with different heat-sensitive areas and air gaps.
• Utilizing titanium as the thermistor material and SiNx as the dielectric layer.
• Simulation using COMSOL Multiphysics and NI Multisim, followed by experimental validation.

Main Results:

• Simulated measurement range: 2 × 10⁻² to 2 × 10⁵ Pa; sensitivity: 52.4 mV/lgPa (N₂ environment).
• Experimental measurement range: 6.6 × 10⁻² to 1.12 × 10⁵ Pa; highest sensitivity: 457.6 mV/lgPa.
• Experimental results surpassed simulation in measurement range, sensitivity, and accuracy.

Conclusions:

• The fabricated MEMS Pirani gauge demonstrates superior performance compared to simulations.
• The device offers a simple structure, ease of manufacturing, and suitability for microcavity integration.
• This MEMS Pirani gauge is a promising solution for monitoring vacuum levels in micro-devices.