基於諧振器 CMOS MEMS 結構之單晶片多感測器設計

Abstract

本論文提出基於標準1P6M 0.18μm CMOS MEMS製程之溫度相關懸臂梁曲率解析模型。 透過此模型，因製程溫度造成的影響，可透過量測少數CMOS層疊組合的曲率萃取關鍵參數，預測所有層疊組合的曲率而無須進行各種組合之量測。文中也進一步分析了由於MEMS封裝的加溫歷程造成懸臂梁的材料降伏，用以解釋層疊結構的應力分布與曲率的關係。此解析模型與白光干涉儀在ASIC相容之 0.18 m 1P6M CMOS MEMS 製程實際製作所量測到的懸臂梁進行驗證確認。這些模型可以用於EDA工具，提供單晶片感測器系統晶片設計因溫度變化造成的懸臂樑結構特性改變的良好預測。 本論文亦提出第一個使用ASIC相容標準CMOS製程並與轉阻放大電路單晶片整合之超低功耗 MEMS 震盪器的設計。它的設計考量是在標準CMOS製程嚴格的設計限制下，試圖達到高Q值與適當的動生阻抗。透過一個高增益超低功耗的支撐轉阻放大電路 (sustaining TIA circuit) 與諧振結構緊密地整合在單一晶片，提供 1.69 W低功耗的32kHz時脈輸出。此設計可嵌入各種SoC應用做為通用的32kHz時脈源 此外，本論文亦提出一個基於MEMS諧振器的多感測器系統單晶片架構，同樣使用標準1P6M 0.18μm CMOS MEMS製程。利用諧振器做為結構單元，多種MEMS感測器包括環境溫度感測器、環境氣壓感測器、加速度感測器和陀螺儀，可以與讀出電路整合在標準ASIC/MEMS製程而不需離廠的前後製程。這個架構可用於IOT應用所需之微小化創新的感知輔助 (sentient assistant) 單晶片設計。

This thesis presents an experimentally-verified analytical model of temperature-dependent yield effects on the curvatures of composite beam structures used in CMOS MEMS. The temperature-dependent effects of a thermal process on the curvatures of composite beams can be predicted by extracting key parameters from the measured curvatures of a limited number of CMOS MEMS composite-layer combinations. The effects due to thermal history in MEMS packaging, which change the characteristics of beam curvatures due to material yield, are further analyzed. The models are verified with measured results from beam structures fabricated by an ASIC-compatible 0.18 m 1P6M CMOS MEMS process using a white light interferometer. These models can be applied in EDA tools to provide good prediction of temperature-dependent properties related to CMOS MEMS beam curvature, such as sensing capacitance, for monolithic sensor SOC design. This thesis also presents the monolithic ultra-low power MEMS oscillator that can be manufactured in the ASIC compatible standard CMOS process and monolithically integrated with TIA circuitry. It is designed for high Q value and moderate motional impedance under strict design constraints of the standard fabrication process. A high gain ultra-low power sustaining TIA amplifier circuit is compactly integrated with the resonator structure on a single die for low-power 32 kHz clock generation. The proposed 1.69W MEMS oscillator can be embedded in common SoC applications monolithically to provide clock sources. In addition, we demonstrated a resonator-based MEMS architecture for multi-sensor SOC applications. A newly developed 0.18m 1P6M CMOS ASIC/MEMS process was adopted to integrate MEMS sensor and circuits monolithically. By using resonators as the building blocks, multiple MEMS sensors including environmental temperature sensor, ambient pressure sensor, accelerometer as well as gyro sensor can be monolithically implemented with the readout circuits by the single standard ASIC/MEMS process without off-fab pre/post processes. The proposed architecture enables compact and innovative sentient-assisted SOC design for the emerging IOT applications.