Multistage chemical etching for high-precision frequency adjustment in ultrahigh-frequency fundamental quartz resonators.
Chemical etching to precisely adjust and to make uniform the thicknesses of 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 consisted 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 single wafer were adjusted to 620 +/- 1.5 MHz, which corresponds to vibrating area thicknesses of 2.2 microm +/- 6 nm. In the temperature-frequency characteristics of these resonators in the single wafer, the difference between the maximum first-order temperature coefficient and the minimum first-order temperature coefficient was equivalent to a cut angle change of two arcminutes. In addition, vibrating areas with an arithmetic mean surface roughness of 0.17 nm on the concave side were produced by this multistage etching.
Iwata
Hirokazu
H
Graduate School of Engineering, Tohoku University, Japan.