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

Pestana, Tiago G.; Pinto, Rui M. R.; Dias, Rosana A.; Martins, Marco; Chu, V.; Gaspar, J.

doi:10.1109/transducers.2019.8808792

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“…Thin-film hydrogenated amorphous silicon (a-Si:H) can be deposited at low temperatures (100 °C) on large-area or lowcost substrates (glass, plastic), allowing the fabrication of thinfilm transistors (TFTs), photodetectors and MEMS in processes compatible with CMOS technology [4,24,25,27]. Recently, the first a-Si:H resonators on 10 μm-thick PI were successfully fabricated by our group [28]. In this paper, that work is continued by directly comparing the performance of a-Si:H thin-film resonators fabricated on 10 μm-thick PI to resonators fabricated on rigid glass substrates.…”

Section: Introductionmentioning

confidence: 99%

Fabrication and characterization of thin-film silicon resonators on 10 $\boldsymbol{{\mu}}$m-thick polyimide substrates

Pestana¹,

Pinto²,

Dias³

et al. 2020

J. Micromech. Microeng.

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MEMS fabricated on polymer substrates can allow for a range of new applications that require bending or lightweight, unbreakable substrates. The surface micromachining of hydrogenated amorphous silicon resonators on 10 µm-thick flexible polyimide substrates is presented. Clamped-clamped (bridges) and clamped-free (cantilevers) resonators are fabricated and characterized, exhibiting quality factors as high as 2.0 × 103 and natural resonance frequencies in the 104–106 Hz range. The deflection of an 80 µm long bridge was measured to be over 100 pm, using laser Doppler vibrometry. The electrical addressing of the devices was demonstrated to be reliable when bent to radii of curvature larger than 10 mm. The resonators on ultra-thin polymer are characterized using different actuation voltages and pressures, showing comparable performance to resonators on rigid (glass) substrates. However, the flexible substrate allows the relaxation of the residual stress of the structural film in clamped-clamped structures, lowering the resonance frequency. Resonators on PI were found to be suitable for mass-sensing applications, achieving a minimum frequency shift detectable Δfmin = 30 Hz which results in a calculated mass sensitivity of 25 pg in vacuum. Ultimately, the reliable performance of the resonators developed in this work make them good candidates for applications that require mass-sensing on ultra-thin, flexible substrates.

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