An innovative 3-D mechanically-coupled array design for MEMS resonator and oscillators

A 3-D mechanically-coupled resonator array has been demonstrated for the first time using CMOS-MEMS technology. A high-performance vertically-coupled (VC) CMOS-MEMS resonator pair was utilized to extend the array topology into 3-D configuration with an on-chip interfaced circuit through a TSMC 0.35 μm 2P4M CMOS-MEMS platform. An array design of 9 VC pairs (N = 18 where N is the number of constituent resonators of an array) was fabricated and characterized with resonance frequency of 5.64 MHz and 0-factor of 1,092. As compared to a single VC pair (N = 2), the Saddle (SA) mode (undesired mode) was eliminated in the array design by the use of electrode phasing at the cost of weak spurious modes around the desired resonance. The 3-D array oscillator was also realized by using an instrumental Lock-in + PLL system. Under same dc biasing, the proposed 3-D array achieves better power handling and phase noise performance over the single VC pair. This technology is expected to bring more functionalities towards medium-scale integrated (MSI) micromechanical circuits.