Electronic tuning of Q and apparent TCf in a piezoresistive micromechanical resonator

This paper reports the electronic tuning of the quality factor (Q) and the apparent temperature coefficient of frequency (TCf) in a dog-bone resonator that is actuated by capacitive drive and sensed using piezoresistive readout. Starting off with an intrinsic Q of ~1.3×105, this device exhibits an amplification of effective Q (up to ~2.4×105) by controlling the bias current. Measured results from several samples repeatedly show similar steady increments of Q within a specific bias current range (0-15mA), and agree with theoretical predictions. As the bias current increases from 0mA to 20mA, it is found that the resonant frequency drift versus ambient temperature can be augmented by as much 2.5 times in terms of the apparent TCf. At the same time, the Q-independent transconductance remains linear with bias current and DC bias voltage from experimental results. We show that the tuning of Q and apparent TCf are due to thermomechanical coupling and can be effectively achieved by varying the bias current. This tuning process is not sensitive to electrostatic actuation.