Multistage chemical etching for high-precision adjustment of resonance frequencies in ultrahigh-frequency-fundamental quartz resonators

Chemical etching to make uniform the thickness of the vibrating areas of multiple resonators in a single wafer was applied to inverted-mesa quartz resonators exciting an ultrahigh-frequency-fundamental thickness vibration. The process consists of five stages, combining high-rate etching for high productivity and low-rate etching for high-precision adjustment. By using this process, the resonance frequencies of 41 resonators in the wafer were adjusted to 620 ± 1.5 MHz, which correspond to thicknesses 2.2 μm ± 6 nm of the vibrating areas.