Design, fabrication and characterization of flexible MEMS accelerometer using multi-Level UV-LIGA

- Conformal z-axis accelerometer fabricated on flexible polyimide substrate.
- Double layer UV-LIGA process deployed for increased sensitivity as high as 187 fF/g.
- Bendability up to 2 cm radius of curvature without performance degradation.
- Resonant frequency varying between 800 Hz and 1100 Hz.

Surface micro-machined z-axis capacitive accelerometers were designed and fabricated on a flexible polyimide substrate, conformal down to 2 cm radius of curvature with the stresses sustained by all layers well below the yield strength for each material. A novel UV-LIGA fabrication technique was developed to realize a thicker proof-mass (8 μm) compared to the spring (3 μm), thus decoupling the two important parameters: the stiffness and the proof-mass to achieve higher sensitivity. Devices with three different sizes were fabricated with the capability of sustaining under distinct amount of acceleration and tuned to frequencies ranging from 600 Hz to 1100 Hz. The largest device, having the area of 960 μm × 960 μm, showed a sensitivity of 187 fF/g with a SNR (Signal to Noise Ratio) of at least 100 when characterized at its resonance frequency of 800 Hz. The applied acceleration was ±4 g in addition to gravitation.