A fully integrated quartz MEMS VHF TCXO

We report on a 32-MHz quartz TCXO fully integrated with commercial CMOS electronics and vacuum packaged at wafer level using a low-temperature MEMS-after quartz process. The novel quartz resonator design provides for stress isolation from the CMOS substrate thereby yielding classical AT-cut f/T profiles and low hysteresis which can be compensated to <; ± 0.2 ppm over temperature using on-chip third-order compensation circuity. The TCXO operates at low power of 2.5 mW and can be thinned to ≤ 300 μm as part of the wafer-level eutectic encapsulation. Full integration with large SOA CMOS wafers is possible using carrier wafer techniques.