Fabrication and Characterization of Glassy Carbon MEMS

This paper describes the fabrication of free-standing high-carbon microstructures by soft-lithographic techniques; these structures ranged in complexity from simple beams to complex, suspended deflectors. Microstructures of polymeric precursors (copolymers of furfuryl alcohol−phenol) to high-carbon solids were fabricated using poly(dimethylsiloxane) (PDMS) molds. Carbonization of these microstructures under argon resulted in mass loss (up to 45%) and shrinkage (up to 20% linearly); the density increased to reach a plateau value of ∼1.5 g/cm3 at ∼900 °C. Microstructures pyrolyzed at 900 °C were electrically conductive, with a conductivity of ∼10-2 Ω cm. Elementary microelectromechanical functions were demonstrated in these microstructures: electrostatic actuation induced deflection or vibrations of suspended structures. The measurement of the frequency of resonance of high-carbon cantilevered beams allowed the determination of Young's modulus for the solid: typical values were ∼15−20 GPa. The microelectromechanical properties of more complex structures (microresonators, light deflectors) were also determined. This paper demonstrates that high-carbon microstructures can be easily fabricated that have potential use as the active components of MEMS.