Enhanced temperature sensitivity of a single CMOS-MEMS resonator via resonant modes in orthogonal axes

A novel CMOS-MEMS composite ring resonator capable of a dual-mode operation has been proposed to enable self-temperature sensing in a single device. To maximize the temperature sensitivity between the dual modes, two resonant modes of a single resonator vibrating in orthogonal axes (i.e., inplane and out-of-plane) are chosen due to the large difference of their temperature coefficients of frequency (TCf´s). By adjusting the constituent ratio and the position of metals and dielectrics through CAD layouts, different TCf´s have been successfully demonstrated in a single CMOS-MEMS resonator. By measuring the TCf´s of the in-plane (INP) and out-of-plane (OOP) mode concurrently, a beat frequency with a temperature coefficient of 72 ppm/°C was characterized. By employing a divider-based scaling concept, an estimated maximum beat frequency sensitivity of 3,244 ppm/°C can be obtained under proper scaling numbers.