在傳統的睡眠呼吸障礙治療流程中，患者需要到醫院睡一個晚上以進行睡眠生理監測。然而偵測患者生理訊號的電極貼片和眾多的傳輸線不僅會造成患者的不適，更會影響患者的睡眠品質。此外，在監測過程中需要一名技師在睡眠室外持續監控記錄狀況，並對整晚記錄下來的數據進行分析判斷，造成專業人力沈重的負擔。
經由本研究團隊建構的雛形平台，期待藉由有效的檢測方式，降低佩戴的複雜度與不適感，使患者可在家自行監測。其睡眠呼吸相關數據由穿戴式感測裝置記錄下來。透過系統後端的無線傳輸及訊號處理，整晚的數據由電腦分析判斷，提供醫師更詳盡的數據以進行病況分析。
此雛形平台前端的感測裝置其中之一為加速度計，用以偵測睡眠呼吸運動產生的胸腹腔運動。為此目的，本研究將設計一個感測解析度合適的CMOS-MEMS電容式加速度計及介面電路。由於CMOS-MEMS易與電路整合，本研究的介面電路，將以截波穩定技巧，避開運算放大器低頻的閃爍雜訊，將電容式加速度計的電容變化訊號轉換為電壓變化訊號輸出。同時，本論文的加速度計也和系統後端的類比數位轉換器、無線傳輸電路及數位控制電路整合成系統單晶片下線。
本論文以TSMC 0.18um 1P6M CMOS製程，結合自行後製程，實現單質量塊雙軸加速度計感測晶片。機械結構面積為625μm × 633μm。量測結果顯示在1.8 V電源供應下晶片功耗976 μW，X軸靈敏度為31.7 μV/G，Y軸靈敏度為0.2 mV/G，X軸等效噪聲為3.16 mG/rtHz ，Y軸等效噪聲為1 mG/rtHz 。

In the formal evaluation tool for sleep-disordered breathing, patients need to go to sleep lab in hospital to do the overnight test. However, the multiple test channels attached to the patient are uneasy. In addition, the whole process needs a professional technician to operate and mark the events after the test. All the procedure is labor-intensive.
In this research, we try to develop an unattended healthcare system to monitor the sleep respiratory disorders at home. The sensor channel must be minimized and the setup has to be simple. By using wireless transmission and signal processing in the back end of the system, the recorded data can be analyzed by computer. This proposal is expected to provide daily respiratory information to assist the medical system for evaluation.
One of the front-end sensors in this prototype platform is accelerometer, which is used to detect the thorax and abdomen respiratory efforts. In this study, a CMOS-MEMS capacitive accelerometer and interface circuits with a resolution applicable to the platform are presented. Chopper stabilization is used to avoid the low frequency noise associated with the active devices. The technique also converts the capacitance change of the capacitive accelerometer to a voltage change at output. Since CMOS-MEMS has the advantage of integrability with circuits, the whole system hardware, including accelerometer, interface circuits, A/D converter, wireless transmission circuits and digital circuits are integrated into a SoC.
The single proof-mass dual-axis accelerometer is implemented in TSMC 0.18um 1P6M CMOS process with in-house post processing. The size of MEMS structure is 625 μm × 633 μm. The power consumption is 976 μW while operates at 1.8 V power supply. The measured sensitivities of X-axis and Y-axis are 31.7 μV/G and 0.2 mV/G, respectively. Noise level of X-axis and Y-axis are 3.16 mG/√Hz and 1 mG/√Hz.

[1] http://en.wikipedia.org/wiki/Polysomnography
[2] http://commons.wikimedia.org/wiki/File:Pediatric_polysomnogram.jpg
[3] C.-W. Wang, “A Prototype of Home-Monitoring System for Patients with Sleep- Disordered Breathing,” M.S. thesis, National Tsing Hua University, Hsinchu, Taiwan, 2014.
[4] J. Wu, G. Fedder, and L. R. Carley, “A low-noise low-offset capacitive sensing amplifier for a 50 μG/√Hz monolithic CMOS MEMS accelerometer,” IEEE Journal of Solid-State Circuits, vol. 39, pp. 722-730, May 2004.
[5] S. S. Tan, C. Y. Liu, L. K. Yeh, Y. H. Chiu, and Klaus Y. J. Hsu, “A new process for CMOS MEMS capacitive sensors with high sensitivity and thermal stability,” Journal of Micromechanics and Microengineering, vol. 21, no.3, pp.1-10, Feb. 2011.
[6] M. Tsai, Y. Liu, C. Sun, C. Wang, C. Cheng and W. Fang, “A 400x400um2 3-axis CMOS-MEMS accelerometer with vertically integrated fully-differential sensing electrodes,” 2011 16th International Solid-State Sensors, Actuators and Microsystems Conference, 2011.
[7] S.-S. Tan, “Design of High-performance CMOS MEMS Accelerometer SoC's,” Ph.D. thesis, National Tsing Hua University, Hsinchu, Taiwan, 2011.
[8] K.R. Williams, K. Gupta, and M. Wasilik, “Etch rates for micromachining processing-Part II,” Journal of Microelectromechanical Systems, vol.12, no.6, pp.761-778, Dec. 2003.
[9] N. Tas, T. Sonnenberg, H. Jansen, R. Legtenberg and M. Elwenspoek, “Stiction in surface micromachining,” Journal of Micromechanics and Microengineering, vol. 6, no. 4, pp. 385-397, Aug. 1996.
[10] G. Zhang, H. Xie, L. de Rosset, and G. Fedder, “A lateral capacitive CMOS accelerometer with structural curl compensation,” Twelfth IEEE International Conference on Micro Electro Mechanical Systems, pp.606-611, Jan. 1999.
[11] H. Luo, G. Fedder, and L. Carley, “A 1 mG lateral CMOS-MEMS accelerometer,” The Thirteenth Annual International Conference on Micro Electro Mechanical Systems, pp.502-507, Jan. 2000.
[12] T. Yen, M. Tsai, C. Chang, Y. Liu, S. Li, R. Chen, J. Chiou, and W. Fang, “Improvement of CMOS-MEMS accelerometer using the symmetric layers stacking design,” 2011 IEEE SENSORS, pp. 145-148, Oct. 2011.
[13] J. Bernstein, R. Miller, W. Kelley, and P. Ward, “Low-noise MEMS vibration sensor for geophysical applications,” Journal of Microelectromechanical Systems, vol. 8, no. 4, pp. 433-438, Dec. 1999.
[14] C. C. Enz and G. C. Temes, “Circuit techniques for reducing the effects of op-amp imperfections: autozeroing, correlated double sampling, and chopper stabilization,” Proceedings of the IEEE, vol. 84, no. 11, pp. 1584-1614, Nov. 1996.
[15] Analog Devices ADXL330 Datasheet
[16] LDS V406 Datasheet
[17] http://cnmm.web.nthu.edu.tw/files/15-1012-9474,c2779-1.php
[18] J. Wu, G. Fedder, and L. Carley, “A low-noise low-offset chopper-stabilized capacitive-readout amplifier for CMOS MEMS accelerometers,” IEEE International Solid- State Circuits Conference, 2002.
[19] M. Tsai, Y. Liu, C. Sun, C. Wang, and W. Fang, “A CMOS-MEMS accelerometer with tri-axis sensing electrodes arrays,” Eurosensor XXIV Conference, vol. 5, pp. 1083-1086, Sep. 2010.
[20] Y.-D. Lin, “Design of a Monolithic Micro-accelerometer with a Readout Circuit of Tunable Sensitivity,” M.S. thesis, National Chiao Tung University, Hsinchu, Taiwan, 2012.
[21] M. Lemkin and B. E. Boser, “A three-axis micromachined accelerometer with a CMOS position-sense interface and digital offset-trim electronics,” IEEE Journal of Solid-State Circuits, vol. 34, pp. 456-468, April 1999.
[22] H. Kulah, J. Chae, N. Yazdi, and K. Najafi, “Noise Analysis and Characterization of a Sigma-Delta Capacitive Microaccelerometer,” IEEE Journal of Solid-State Circuits, vol. 41, no. 2, pp. 352-361, Feb. 2006.
[23] W. Kuehnel, “Modeling of the mechanical behavior of a differential capacitor acceleration sensor,” Sensors Actuators A: Physical, vol. 48, no. 2, pp. 101-108, May 1995.
[24] M. Bao and H. Yang, “Squeeze film air damping in MEMS,” Sensors and Actuators A: Physical, vol. 136, no. 1, pp. 3-27, May 2007.
[25] H. Sun, D. Fang, K. Jia, F. Maarouf, H. Qu, and H. Xie, “A Low-Power Low-Noise Dual-Chopper Amplifier for Capacitive CMOS-MEMS Accelerometers,” IEEE Sensors Journal, vol.11, no.4, pp.925-933, April 2011.
[26] H. Sun, F. Maarouf, D. Fang, K. Jia, and H. Xie, “An improved low-power low-noise dual-chopper amplifier for capacitive CMOS-MEMS accelerometers,” 3rd IEEE International Conference on Nano/Micro Engineered and Molecular Systems, pp.1075-1080, Jan. 2008.
[27] Makinwa, “Dynamic offset cancellation techniques in CMOS,” IEEE International Solid-State Circuits Conference, 2007.