本論文提出一加速度感測系統，整合類比至數位轉換器(ADC)於單晶片中，採用分時多工之類比前端讀出電路，改善分頻多工電壓擺幅會被三軸訊號均分的缺點。此加速度感測系統於0.18 μm CMOS-MEMS製程下完成。並於類比前端讀出電路中，提出一功率控制的方法，可以讓使用者根據使用需求，自由的切換單軸與多軸模式，於單軸模式下有較低的功率消耗，以提高電池的使用時間。
對於MEMS三軸加速度計，量測結果其三軸之共振頻率分別為4.7 kHz、4.3 kHz、4.28 kHz。此分時多工讀出電路操作範圍為±16g，於加速度振動量測平台上，量測到的x軸、y軸、z軸的靈敏度分別為79.43 mV/g、44.29 mV/g、13.25 mV/g，解析度分別為1.78 mg/√Hz、1.01 mg/√Hz、3.38 mg/√Hz。並於單軸模式下，功率消耗為256.2 μW；三軸模式下，功率消耗為779.4 μW。此外，10-bit類比至數位轉換器操作於50 kS/s的取樣頻率下，量測到的SNDR為50.21 dB，其對應的ENOB為8.05。

In this thesis, an acceleration sensing system is proposed, which integrates an analog-to-digital converter (ADC) into a single chip. We adopt time division multiplexing to realize the analog front-end readout circuit and improve the disadvantage in frequency division multiplexing that the voltage swing will be shared by the three-axis signals. This acceleration sensing system is implemented in 0.18 μm CMOS-MEMS process. And in the analog front-end readout circuit, a power controller is proposed, which can switch between single-axis and multi-axis mode freely according to user mode. There is less power consumption in the single-axis mode to extend the battery life.
For the MEMS three-axis accelerometer, the measured resonance frequencies are 4.7 kHz, 4.3 kHz, and 4.28 kHz, respectively. The sensing range of the three-axis accelerometer is ±16g. On the acceleration and vibration measurement platform, the measured sensitivities of x-, y-, z-axis are 79.43 mV/g, 44.29 mV/g, and 13.25 mV/g, respectively. The resolutions are 1.78 mg/√Hz, 1.01 mg/√Hz, 3.38 mg/√Hz, respectively. In single-axis mode, the power consumption is 256.2 μW. On the other hand, in 3-axis mode, the power consumption is 779.4 μW. In addition, the 10-bit analog-to-digital converter operates at a sampling frequency of 50 kS/s. The measured SNDR is 50.21 dB, the corresponding ENOB of 8.05.

摘要 i
ABSTRACT ii
致謝 iv
CONTENTS v
LIST OF FIGURES viii
LIST OF TABLES xiii
Chapter 1 Introduction 1
1.1 Motivation 1
1.2 Organization 4
Chapter 2 MEMS Accelerometer Design and Simulation 5
2.1 CMOS-MEMS Fabrication 5
2.1.1 Process 5
2.1.2 CMOS-MEMS Process Layout Rules 7
2.2 Model and Design of MEMS Sensor 11
2.2.1 Mass-Spring-Damper Model for MEMS Motion System 11
2.2.2 Structure of MEMS Accelerometer 13
2.2.3 Operational Principle of MEMS accelerometer 16
2.3 Accelerometer Behavior Simulation 20
2.3.1 Modal Analysis 20
2.3.2 Coupled Electromechanical Analysis 22
Chapter 3 Readout Circuit Design and Simulation 28
3.1 System Architecture 28
3.2 Analog Front-end Circuit Design 29
3.2.1 Noise Reduction Technique – Chopper 29
3.2.2 Time Division Multiplexing 30
3.2.3 First Stage Amplifier Design and Simulation 31
3.2.4 2nd Gain Stage Amplifier Design and Simulation 35
3.2.5 Track & Hold Circuit 38
3.2.6 Voltage Buffer Design and Simulation 39
3.2.7 Second-order Low Pass Filter Design and Simulation 41
3.2.8 Clock Generator Circuit Design 44
3.2.9 Power Control for Single-axis and Multi-axis Mode Switching 45
3.3 A/D Converter Design 47
3.3.1 Monotonic-Switching SAR ADC 47
3.3.2 Analysis of Switching Energy in DAC Network 49
3.3.3 Bootstrapped Switch Design and Simulation 51
3.3.4 Dynamic Comparator Design and Simulation 53
3.3.5 Asynchronous SAR Control Logic 58
3.3.6 Capacitor Array 59
Chapter 4 Sensor and Readout Circuit Co-simulation 60
4.1 Design Flow of Sensor and Analog Front-end Circuit 60
4.2 Co-simulation of Sensor and Analog Front-end Circuit 62
4.3 Design Flow of A/D Converter 67
4.4 Simulation of Monotonic-Switching SAR ADC 68
Chapter 5 Measurement Results 72
5.1 Measurement Results of the MEMS Structure 75
5.1.1 SEM View of the MEMS Accelerometer 75
5.1.2 Curl Measurement in White Light Interferometer 78
5.1.3 Frequency Response of the MEMS Accelerometer 83
5.2 Measurement Results of the Sensor and Front-end Analog Circuit 87
5.3 Measurement Results of the SAR ADC 93
5.3.1 Dynamic Performance 96
5.3.2 Static Performance 97
Chapter 6 Conclusions and Future Work 99
6.1 Conclusions 99
6.2 Future Work 99
REFERENCES 100

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