臺灣博碩士論文加值系統

本論文驗證了具有感測器誤差校正功能低功耗/低雜訊之互補式金屬氧化物半導體微機電製程加速度器單晶片之設計技術。感測器因製程飄移所造成之靜態電容誤差往往比運動所產生之電容變化量來得大許多，若無適當的修正誤差則此一晶片便無法使用。本論文所提出的兩種校正機制具有低功耗、面積小之優勢，而量測結果也證明此一互補式金屬氧化物半導體微機電製程所製造之加速度器單晶片不論是在靈敏度、線性度、功率消耗或是輸出雜訊的表現均和商用產品具有相匹敵之性能。而利用極低電壓電路設計技巧所設計之0.6 伏特操作加速度器更具有0.2 毫瓦之低功耗，可偵測0.01 個重力加速度之變化，並具有一個14 位元輸出之三角積分類比/數位轉換器。最後本論文提出了一個以交換電容式架構為基礎之多感測器讀取電路，其以分時多工之機制可以提供電壓、電流、電阻和電容類型之轉換。利用此一通用型讀取電路，一個結合三軸加速度器、三軸磁力計以及ARM M0 微處理器之單晶片除了可以執行虛擬陀螺儀演算法，並提供了一個低功耗、低成本之虛擬陀螺儀解決方案。

This dissertation presents the design of low-power low-noise monolithic CMOS MEMS accelerometers using area-efficient digital offset trimming techniques to compensate for process variations caused by sensor capacitance mismatches. The consistent distributions of resonant frequency and sensitivity indicates that the wafer-level 0.18-μm CMOS MEMS process is suitable for integrated inertial sensors. The simulation and measurement results for the designed and fabricated chips show good linearity and noise performance, which are comparable to those seen with commercial products. A 0.6-V monolithic CMOS MEMS accelerometer design with automatic offset trimming capability is also demonstrated in this dissertation, in order to achieve further reductions in the power consumption of the sensor readout circuits. With only 0.2-mW power consumption, the readout circuit can detect smaller than 0.01 g acceleration with the digital output provided by a low-voltage 14-bit ΣΔ ADC. Finally, a multiplexed multi-sensor generic interface circuit which can support the voltage-to-voltage, currentto-voltage, resistance-to-voltage, and capacitance-to-voltage conversion requirements of different sensors is proposed. This feature makes multi-sensor SoC possible when integrating an embedded microprocessor and memory in the CMOS MEMS process. A test chip, which includes a three-axis CMOS MEMS accelerometer, the generic interface circuit, an incremental ΣΔ ADC, and an ARM M0 microprocessor, was fabricated. When combined with a three-axis magnetic sensor which needs some post processing after finishing all CMOS MEMS processes, this test chip can provide a low-power and low-cost three-axis virtual gyroscope with commercial applications.

Abstract (Chinese) i
Abstract (English) iii
Acknowledgments v
Table of Contents vii
List of Tables ix
List of Figures x
Chapter 1. Introduction 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 CMOS MEMS Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Sensor Readout Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3.1 Voltage to Voltage Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3.2 Current to Voltage Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.3.3 Resistance to Voltage Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.3.4 Capacitance to Voltage Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.4 Organization of the Dissertation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Chapter 2. Monolithic Capacitive Accelerometer Design . . . . . . . . . . . . . . . . .13
2.1 Introduction of MEMS Accelerometers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2 X-Axis Accelerometer Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
2.3 Readout Circuit Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.4 Sensor Mismatch and Automatic Offset Trimming Technique . . . . . . . . . . 27
2.5 Multi-Axis Accelerometer Readout Architecture . . . . . . . . . . . . . . . . . . . . . 30
2.6 Measurement Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Chapter 3. Low-Voltage Low-Power Capacitive Accelerometer Design . . . . . . 42
3.1 Introduction of Low-Voltage Circuit Design . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.2 Fully-Differential Capacitive Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.3 Low-Voltage OTA and CMP Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49
3.4 Sensor Offset Trimming for Low-Voltage Capacitive Accelerometer . . . . . .55
3.5 Low-Voltage Sigma-Delta ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58
3.6 Noise Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
3.7 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
3.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66
Chapter 4. Generic Sensor Readout Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
4.1 Introduction of Virtual Gyroscopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68
4.2 Z-Axis Accelerometer Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
4.3 Generic Readout Circuit Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
4.4 Incremental Sigma-Delta ADC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79
4.5 SoC Implementation of a Virtual Gyroscope . . . . . . . . . . . . . . . . . . . . . . . . 81
4.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .85
Chapter 5. Conclusions and Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86
5.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
5.2 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

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