Silicon/quartz bonding and quartz deep RIE for the fabrication of quartz resonator structures

In this paper, silicon/quartz bonding and quartz deep RIE (DRIE) processes have been developed to fabricate micromechanical quartz resonator structures. A low temperature (<= 300 degrees C), plasma-assisted silicon/quartz bonding condition that can provide the maximum bonding shear strength of 10 MPa has been experimentally constructed. The bonded silicon wafer was first applied to an etch mask of quartz, and thick quartz microstructures (similar to 50 mu m) have been fabricated by deep RIE of quartz with a gas mixture of C4F8 and He. In addition, a simple fused-quartz freestanding cantilever structure has been successfully fabricated by using the bonded silicon wafer not only for an etch mask layer but also for a substrate for quartz structures. The developed bonding and deep RIE processes, in combination with a proper metallization technique, are expected to be used for the wafer-level fabrication of freestanding quartz resonators.