Thin-Film Silicon Resonators on Ultra-Flexible 10 Micrometer-Thick Polyimide Substrates

This work presents electrostatically-driven micromechanical (MEMS) flexural resonators made of thin-film hydrogenated amorphous silicon (a-Si:H), microfabricated on a 10 μm-thick polyimide (PI) substrate. Innovations in this work comprise: a) successful microfabrication of a-Si:H resonators using low temperature surface micromachining on ultra-thin PI, compatible with polymeric, flexible and stretchable substrates; b) electromechanical characterization of resonators on very thin PI substrates, with resonance frequencies and quality factors comparable to those observed in rigid glass and silicon substrates; c) reliable electronic addressing of the devices when the substrate is bent to radii of curvature larger than 10 mm; d) mode shape characterization of the resonators using Laser Doppler Vibrometry (LDV) techniques; e) FEM simulation of the devices' frequency response. These MEMS preserves the mechanical properties of Si in ultra-flexible substrates and could potentially be applied to wearables, distributed sensing and interfacing with the human body.