Highly-sensitive wafer-scale transfer-free graphene MEMS condenser microphones

Roberto Pezone*, Sebastian Anzinger, Gabriele Baglioni, Hutomo Suryo Wasisto, Pasqualina M. Sarro, Peter G. Steeneken, Sten Vollebregt*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

1 Citation (Scopus)
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Abstract

Since the performance of micro-electro-mechanical system (MEMS)-based microphones is approaching fundamental physical, design, and material limits, it has become challenging to improve them. Several works have demonstrated graphene’s suitability as a microphone diaphragm. The potential for achieving smaller, more sensitive, and scalable on-chip MEMS microphones is yet to be determined. To address large graphene sizes, graphene-polymer heterostructures have been proposed, but they compromise performance due to added polymer mass and stiffness. This work demonstrates the first wafer-scale integrated MEMS condenser microphones with diameters of 2R = 220–320 μm, thickness of 7 nm multi-layer graphene, that is suspended over a back-plate with a residual gap of 5 μm. The microphones are manufactured with MEMS compatible wafer-scale technologies without any transfer steps or polymer layers that are more prone to contaminate and wrinkle the graphene. Different designs, all electrically integrated are fabricated and characterized allowing us to study the effects of the introduction of a back-plate for capacitive read-out. The devices show high mechanical compliances Cm = 0.081–1.07 μmPa−1 (10–100 × higher than the silicon reported in the state-of-the-art diaphragms) and pull-in voltages in the range of 2–9.5 V. In addition, to validate the proof of concept, we have electrically characterized the graphene microphone when subjected to sound actuation. An estimated sensitivity of S1kHz = 24.3–321 mV Pa−1 for a Vbias = 1.5 V was determined, which is 1.9–25.5 × higher than of state-of-the-art microphone devices while having a ~9 × smaller area. (Figure presented.).

Original languageEnglish
Article number27
Number of pages9
JournalMicrosystems and Nanoengineering
Volume10
Issue number1
DOIs
Publication statusPublished - 2024

Funding

The authors thank the Delft University of Technology Else Kooi Lab staff for processing support and Arthur Campos de Oliveira for helpful discussions. This project has received funding from European Union’s Horizon 2020 research and innovation program under Grant Agreement No. 881603 (Graphene Flagship).

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