Polycrystalline silicon-carbide surface-micromachined vertical resonators-part I: growth study and device fabrication

This manuscript is the first of a two-part series describing the fabrication and testing of MHz frequency, polycrystalline silicon-carbide (poly-SiC) micromechanical resonators made from films deposited by atmospheric-pressure chemical-vapor deposition (APCVD). In Part I, the development of deposition and patterning techniques suitable for the fabrication of vertically actuated, clamped-clamped beam resonant structures is detailed. Recipe development involved film deposition and material analysis on both planar and patterned substrates. We found that a carbonization-based deposition process modeled after epitaxial growth of 3C-SiC on Si produced the highest quality poly-SiC films for use with sub-micron thick polysilicon sacrificial layers, regardless of topology. Devices utilizing beam thicknesses up to 1 μm were fabricated and successfully released. Details about the testing of the released structures are presented in Part 2 of this series (see Wiser, Tabib-Azar, Mehregan, and Zorman, "Polycrystalline silicon-carbide surface-micromachined vertical resonators-Part II: Electrical testing and material property extraction", J. Microelectromech. Syst., vol. 14, no. 3, Jun. 2005).