Electrical control for wet etching of quartz resonators

We report a method to etch multiple quartz crystal resonators in parallel to accuracy better than +/-50 ppm by measuring the sample resonant frequency with a network analyzer while the sample is wet etched. The etch rate of individual resonators is fine tuned with electrical bias to compensate local etch rate and wafer thickness variations. This allows for the final frequency of the resonators across the wafer to be within the required specifications without trimming. By eliminating the need for the final sample trimming, the manufacturing cost can be lowered and further resonator miniaturization is feasible.