Abstract
In this work, we use mature CMOS-MEMS platforms to design and realize a thermal-drive piezoresistive-sense resonator. The frequency of the MEMS resonator is 5MHz with the Q-factor of 12,000 in vacuum. This thesis describes the principle and operation of the proposed thermal-drive piezoresistive-sense resonators where the characteristics of the devices are analyzed by finite element simulation and electronic design software. First, a power supply (KEITHLEY) provides an adequate DC current source with an ac signal of the network analyzer to the structure. When the internal loop gain is large enough, the structure will resonate at its nature frequency and generate an ac voltage signal by the piezoresistive effect. In terms of the design, we use two different platforms (i.e., D35 and T18 CMOS-MEMS platforms) to realize our structures and find out their figure of merits (FOMs). In order to obtain the maximum piezoresistive change, the bulk mode (i.e., longitudinal mode) is adopted. And we can not only improve the piezoresistive-sense efficiency using different layout designs but also realize the micro-scale structures by a three-step post-process. The measurement data under different experimental setups and operations are demonstrated. The results are compared with simulations to verify the proposed models. Finally, we will integrate the MEMS with PCB electronics to compensate the loss of the MEMS devices to achieve oscillation. The measurement results include the Open-Loop and Closed-Loop measurements. The Closed-Loop configuration is measured by a spectrum analyzer to characterize the oscillation and phase noise while the frequency counter is utilized to measure the frequency stability of the MEMS oscillators.