Bulk wave quartz resonators fabricated by a hollow cathode RF plasma etching technique

Vibration modes in thin quartz membranes are considered. A hollow cathode maskless plasma etching method for fabrication of the membranes is presented. A special geometric arrangement of electrodes and substrata allows the complete plasma structure to be transferred to the substrata area during the etching process. The process has successfully been applied for preparing membranes with plane-convex and plane-parallel shape and thicknesses of less than 5 μm. The membranes were used for realization of bulk acoustic wave resonators at fundamental frequencies over 60 MHz and their electrical characteristics are presented