An Intrinsically Temperature-Compensated Fully Differential CMOS-MEMS Resonator with Dual-Resistor Piezoresistive Detection

In this work, a fully differential CMOS-MEMS resonator with capacitive actuation and dual-resistor piezoresistive (PZR) detection is realized based on a square plate resonator (SPR) in a 0.35μm CMOS platform. The differential scheme is enabled by positioning piezoresistors at locations with complementary stresses during vibration, which not only provides out-of-phase motional currents (± i
m
) for differential PZR sensing but also eliminates the DC voltage difference between the sensing terminals. A complete model of differential transconductance (g
mdd
) is also derived to provide further design insights. The proposed SPR resonator is implemented using metal-oxide composite films and polysilicon resistors, which demonstrates an operation frequency of 10.8 MHz, a quality factor (Q) of 850, g
mdd
of 2.2 μS, and a signal-to-background ratio of 25 dB. In addition, with the help of metal-oxide composite structure and residual stresses in the films, a low temperature coefficient of frequency (TCF) of only +6.5 ppm/°C is extracted through built-in self-test, which is 10X better than conventional CMOS-MEMS resonators.