Highly Sensitive Polymer Micro-Mesh for Measurement of Vacuum Packaged MEMS Devices

The paper presents a polymer (SU-8) based MEMS Pirani gauge for the estimation of vacuum levels in packaged MEMS devices. The lower thermal conductivity of SU-8 (∼0.2 W/m.K) offers enhanced sensitivity without incurring extra power consumption. Moreover, the micro-mesh structure offers effective coupling of ambient air/gas with the heated membrane resulting in improved thermal losses. Finite-Element-Model (FEM) analysis of the mesh are carried out using COMSOL Multiphysics®. A prototype structure is fabricated using a 3D lithographic technique to check the practicality of the idea. The simulation results show that the device can be used to measure vacuum levels from 4 Pa to 10E4 Pa. The linear range sensitivity of the simulated device is
$\sim 2.35 \times 10\mathrm{E} 2\ {}^{\circ}\mathrm{C}/\text{mW}/\text{decade}-\text{Pa}$
.