Frequency Stability of Wafer-scale Film Encapsulated Silicon Based Mems Resonators

The stability of resonant frequency for single wafer, thin film encapsulated silicon MEMS resonators was investigated for both long term operation and temperature cycling. The resonant frequencies of encapsulated resonators were periocidcally measured at 25°C ± 0.1°C for > 9,000 hours, and the resonant frequency variation remained within the measurement uncertainty of 3.1 ppm and 3.8 ppm. Also, the resonantors were temperature cycled for 680 cycles between -50°C and 80°C, measuring the resonant frequency each time the temperature reached 30°C. Again, the change in resonant frequency was seen to remain within the measurement uncertainty. This demonstrates stability of resonant frequency for both long-term operation of more than a year and huge number of temperature cycling, emphasizing the stability of both the resonator and the package.