Toward ultimate performance in GHZ MEMS resonators: Low impedance and high Q

In this paper we report a ~1GHz lateral extensional thin-film piezoelectric-on-substrate (TPoS) resonator with an unloaded quality factor (Q) of 6700 in air (frequency-quality factor product of 6.6×10¹²), a motional impedance of ~160¿, and a linear thermal coefficient of frequency of -29ppm. To achieve such low impedance the 21^st harmonic resonance mode of a single crystalline silicon block is excited while the near-resonance spurs are suppressed by rigidly supporting the resonator with multiple anchors. Results measured from identical devices each supported with various anchor designs are compared and the effectiveness of increasing rigidity to remove the near-resonance distortions is confirmed. With the reported performance in this work, the fabricated ~1 GHz resonator is suitable for very low-power and low-noise high-frequency oscillator applications.