| MEMS gyroscopes, accelerometers, and resonators have been proposed as solutions for a variety of sensing applications. Complementary metal-oxide semiconductor (CMOS) MEMS devices fabricated concurrently with CMOS electronics show particular promise for sensing applications due to their compatibility with CMOS electronics.;In CMOS MEMS devices, there are several metal-dielectric interfaces within the CMOS stack. Trapped charges at these interfaces can modify the electric fields applied to the device, altering device behavior (e.g., resonant frequency, pull-in voltage, sensitivity). This work characterizes and models dielectric charging in CMOS MEMS resonators to promote understanding of charging mechanisms in CMOS MEMS.;The hypothesis is that dielectric charging behavior is repeatable and able to be captured in a model to guide the design of future CMOS MEMS devices. The work addresses questions about the nature and location of dielectric charge in the CMOS MEMS stack. The electric field transient response of both CMOS MEMS resonators and thin film dielectric test structures is characterized. A fitting function, the stretched exponential function, is employed to describe the charge over time and provide additional insights about charge conduction mechanisms within the dielectrics. Contributions of this work include characterization of dielectric charging in two resonator designs and thin film samples, and a Cadence model of the transient effects of dielectric charging on CMOS MEMS devices.;Additionally, a current technology node CMOS MEMS accelerometer and a mode-matched gyroscope fabricated in a legacy process were designed. The gyroscope demonstrates a new tuning scheme for mode matching based on electro-thermal actuation. This tuning mechanism requires lower supply voltages than previously demonstrated electrostatic tuning mechanisms. Fabrication challenges prevent testing of the inertial sensors, but future work in fabrication may enable device characterization. |
