Doping-Induced Temperature Compensation of Thermally Actuated High-Frequency Silicon Micromechanical Resonators

Temperature compensation of thermally actuated high-frequency single crystalline silicon micromechanical resonant structures via high concentration n-type doping has been demonstrated in this paper. The effect of doping level, structural dimensions, and bias current on temperature coefficient of frequency (TCF) for such resonators has also been investigated. It has been shown that the large negative TCF of the silicon resonators (-38 ppm/°C) can be highly suppressed by doping the devices with a high concentration of phosphorous. The TCF can also be fine tuned by changing the operating bias current of the resonators. Temperature drift characteristics for several high- frequency I-shaped resonators thermally doped under different conditions have been measured and compared. For an ideal doping level, an overall linear temperature drift of -3.6 ppm over the range of 25°C to 100°C, which is equivalent to a TCF as low as -50 ppb/°C, has been demonstrated for one of the resonators. The results in this paper imply the possibility of having low-cost high-frequency thermally actuated resonators with a near-zero TCF.