Abstract
Capacitive MEMS oscillator structure and Phase-Looked Loop are integrated in the same chip through the CMOS-MEMS integration technology. This work is the first proposed to use the PLL output to drive the MEMS oscillator structure. By deposition of oxide or parylene on MEMS oscillator structures, it will change the structure frequency caused by the change of mass, and thus it shows the result in the output of the phase-locked loop to achieve the purpose of mass sensing. In the phase-locked loop, we use a full analog design in this work, which mainly contains a phase detector, a voltage-controlled oscillator and a loop filter. The thesis includes stability analysis, circuit simulation and measurement. In the MEMS oscillator, we design four different structures, with each having a 4×4 array on the chip to form a 8×8 array. The resonant frequencies are 228 kHz, 449 kHz, 614 kHz and 796 kHz, and the simulated sensitivities are 3.5 Hz/pg, 8.67 Hz/pg, 17 Hz/pg and 24.42 Hz/pg. The area of the structure is 100μm×30μm. This thesis includes the simulation and measurement of the resonant frequency, displacement, capacitance and sensitivity of the MEMS structure. And we also analyze and discuss the problems we have encountered. Finally, in the part of mass sensing, we choose Parylene as the material for deposition. The main reason is that it can be deposited at room temperature, and it is more convenient for the study. We also achieved the purpose of mass sensing by measuring the change of frequency by the change of mass.