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 pm-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; c) 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.