Temperature Compensation In Cmos-Mems Oscillators Via Folded-Anchor Resonator Geometrical Tuning

Temperature-induced frequency drift is a major concern in the MEMS resonators field for time referencing or sensing applications. Besides the paramount advantages regarding SoC integration, cost and performance of CMOS-MEMS solutions, the limited performance of the available materials in CMOS technologies results into resonators with elevated temperature coefficient (TCF). Various approaches have been proposed to reduce such dependence like alternate geometries, material composite structures, μ-oven compensation strategies and electrical stiffness tunning schemes. In this work we present, for the first time, a monolithic CMOS-MEMS single-layer plate resonator with specific folded anchors that reduce by two orders of magnitude the temperature impact, reporting experimentally an overall frequency shift of 760 ppm over a temperature span from 20°C to 50°C. The main advantage of this proposal is its mechanical design-level implementation while allowing the application of additional active strategies. Moreover, the adoption of a single-layer approach makes this technique especially suited to inertial mass sensing applications since the distributed mass sensitivity is kept optimal.