Micromechanical properties of amorphous,nanocrystalline and transition phase hot-wire thin-silicon MEMS

Thin film silicon MEMS-based electrostatic bilayer microresonators are fabricated on glass substrates by hot-wire chemical vapor deposition with the silicon structural layer spanning the amorphous to nanocrystalline transition. Five sets of bridge and cantilever microresonators are fabricated with hydrogen dilutions of 0%, 60%, 85%, 90% and 95%. The silicon structural layers for 0% and 60% dilution are amorphous, for 90% and 95%, nanocrystalline, and for 85% dilution, an intermediate structure. All processing steps were carried out at temperatures ⩽110 °C. Microresonators are electrostatically actuated and the resulting deflection is optically monitored. The crystallinity of the structural layer does not have an observable effect in the rigidity of the resonators. The quality factor shows a maximum at 85% H₂ dilution, corresponding to a material with a structure intermediate between amorphous and nanocrystalline. A sharp decrease in quality factors is observed for higher dilutions.