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Performance Enhancement of Integrated Micromechanical Resonators Using Generalized CMOS-MEMS Platforms
Dissertation

Performance Enhancement of Integrated Micromechanical Resonators Using Generalized CMOS-MEMS Platforms

Chen, Wen-Chien
Doctor of Philosophy (PHD), 國立清華大學, 動力機械工程學系
2012

Abstract

金氧半導體微機電 射頻微機電 製程平台 全整合式 電容式 微機械共振器 甚高頻 吸附效應 次微米 頻率調控 全差分 二氧化矽結構 音叉 方形板 體聲波 高Q值 溫度補償 複合結構 CMOS-MEMS RF-MEMS platform fully-integrated capacitively-transduced micromechanical resonator VHF pull-in deep-submicron frequency tuning fully-differential oxide structure tuning fork square plate bulk acoustic High-Q temperature compensation composite structure
The CMOS-MEMS technology with many advantages, including smaller footprints size, without noise from bond pad, and standard foundry process, is utilized in this dissertation to develop various capacitively-transduced HF/VHF micromechanical resonators with several unique performances targeted for sensor, timing reference, and RF applications. To attain this goal, two generalized releasing post-process, such as oxide wet etching and metal wet etching techniques, compatible with 0.35 m 2P4M and 0.18 m 1P6M CMOS processes, were successfully developed to fabricated metal-type and oxide-type integrated resonators, respectively, with diverse structural designs as well as different material configurations. In addition to post-process development, this dissertation attend to improve main consideration of MEMS resonator design issues, such as motional impedance (Rm), quality factor (Q), thermal stability, frequency tuning, power handling capability, and feedthrough cancellation, through (1)gap reduction mechanism, (2)high-Q material and tiny-support, (3)oxide-metal composite, (4)elegant structural design, (5)resonator-array and bulk mode vibration, and (6)fully-differential electric setup, respectively, successfully demonstrating CMOS-MEMS resonators with better characteristics of relative low-Rm, high-Q, temperature compensated capability, quasi-linear frequency tuning ability, high power handling, large signal to noise ratio, than previous CMOS-MEM works. In addition, this dissertation also derive a generalized theoretical model of passive temperature compensation for composite bulk mode resonators, capable of further controlling its temperature coefficient of frequency (TCf) Such performance improved results might benefit the future integrated micromechanical oscillator design for timing or frequency reference in consumer electronics.

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