本論文為設計一出平面的加速度計外，同時也完成了一差動式電容感測電路設計，並整合於單晶片上。整體架構包含兩大部分，分別為微機械結構體以及差動式的感測電路。首先，在微元件上使用長短電極的配置方式組成感測電極，並利用ANSYS軟體進行機械結構上之應力模擬分析，以確定元件的可行性；在感測電路上，利用上下兩組的電容電壓轉換器與後端的減法器所構成，藉由HSPICE軟體的分析，模擬所設計之電容感測電路之性能，模擬結果顯示電容感測電路具備高線性度與高靈敏度的特性。整個元件透過國家晶片系統設計中心(CIC)，利用TSMC 0.35 μm Mixed-Signal 2P4M Polycide 3.3/5 V製程進行製作，其後再透過兩道的後製程將微元件懸浮。實際量測上，在電路部份，差動式電容感測電路之量測結果與模擬值相當接近，代表此電路能成功地運作，其靈敏度約為21.32 mV/fF/V，解析度約為0.28 aF/√Hz；而整體元件的量測上，也證明了本元件能正常的作動，其共振頻為4.39 kHz，靈敏度為9.8 mV/g/V，非線性度則為4.7 ％，雜訊位準為0.61 mg/√Hz，而且與其他軸向的耦合不大，如同理論分析所示，本元件架構具有良好的解析度與線性度。

This study presents a capacitance sensing circuit with high sensitivity and linearity, by integrating a vertical microaccelerometer. The proposed capacitive sensing circuit is composed of a capacitance-voltage converter to amplify the readout signals, and a differential circuit, which is capable of reducing common-mode noise and offering high resolution. The microstructure and the capacitive sensing circuit were fabricated through TSMC 0.35 μm mixed-signal 2P4M polycide 3.3/5 V process. Experimental results demonstrated that the sensing circuit exhibited a linear capacitance-to-voltage relation. The sensitivity and resolution of differential sensing circuit are 21.32 mV/fF/V and 0.28 aF/√Hz, respectively. Moreover, the microstructure is successfully integrating with capacitive sensing circuit, in which with high resolution and linearity. The sensitivity and nonlinearity of the accelerometer are 9.8 mV/g/V and 4.7 ％, respectively.

[1] B. Puers and W. Sansen, “ A New Uniaxial Accelerometer in Silicon Based on the Piezojunction Effect,” IEEE Transactions on Electronic Devices, ED-35, pp. 764 - 770, 1988.
[2] P. Scheeper, J. O. Gullov, and M. Kofoed, “ A Piezoelectric Triaxial Accelerometer,” Journal of Micromechanics and Microengineering, Vol. 6, pp. 131 - 133, 1996.
[3] L. M. Roylance and J. B. Angell, “ A Batch-fabricated Silicon Accelerometer,” IEEE Transactions on Electronic Device, ED-26, pp. 1911 - 1917, 1979.
[4] A. Partridge, J. K. Reynolds, B. W. Chui, E. M. Chow, A. M. Fitzgerald, L. Zhang, N. I. Maluf, and T. W. Kenny, “ A High-performance Planar Piezoresistance Accelerometer,” Journal of Microelectromechanical Systems, Vol. 9, pp. 58 - 66, 2000.
[5] T. Mineta, S. Kobayashi, Y. Watanabe, S. Kanauchi, I. Nakagawa, E. Wuganuma, and M. Esashi, “ Three-axis Capacitive Accelerometer with Uniform Axial Sensitivities,” Journal of Micromechanics and Microengineering, Vol. 6, pp. 431 - 435, 1996.
[6] K. H. L. Chau, S. R. Lewis, Y. Zhao, R. T. Howe, S. F. Bart, and R. G. Marcheselli, “ An Integrated Force-balanced Capacitive Accelerometer for Low g Application,” Sensor and Actuator : A, Vol. 54, pp. 472 - 476, 1966.
[7] Y. Matsumoto, M. Nishimura, M. Matsuura, and M. Ishida, “ Three-axis SOI Capacitive Accelerometer with PLL C-V Converter,” Sensors and Actuators A, Vol. 75, pp. 77 - 85, 1999.
[8] P. M. Zavaracky, B. McClelland, K. Warner, J. Wang, F. Hartley, and B. Dolgin, “ Design and Process Considerations for a Tunneling Tip Accelerometer,” Journal of Micromechanics and Microengineering, Vol. 6, pp. 352 - 358, 1996.
[9] C.-H. Liu and T. W. Kenny, “ A High-precision, Wide-bandwidth Micromachined Tunneling Accelerometer,” Journal of Microelectromechanical Systems, Vol. 10, pp. 425 - 433, 2001.
[10] CICeNEWS，國家晶片系統設計中心電子報，Vol. 75，2007.
[11] W. Yun, R. T. Howe, and P. R. Gray, “Surface Micromachined, Digitally Force-Balanced Accelerometer with Integrated CMOS Detection Circuitry,” Solid-State Sensor and Actuator Workshop, 1992. 5th Technical Digest., IEEE, pp. 126 - 131, 1992.
[12] H. Xie and G. K. Fedder, “ A CMOS Z-axis Capacitive Accelerometer with Comb-Finger Sensing,” IEEE International Conference Micro ElectroMechanical Systems, pp. 496 - 501, 2000.
[13] G. Zhang, H. Xie, L. E. de Rosset, and G. K. Fedder, “ A Lateral Capacitive CMOS Accelerometer with Structural Curl Compensation,” the 12th IEEE International Conference Micro ElectroMechanical Systems (MEMS’ 99), pp. 606 - 611, 1999.
[14] T. Tsuchiya and H. Funabashi, “ A z-axis Differential Capacitive SOI Accelerometer with Vertical Comb Electrodes, ” Sensors and Actuators A, Vol. 116, pp. 378 - 383, 2004.
[15] C. M. Sun, C. W. Wang, and W. Fang, “On the Sensitivity Improvement of CMOS Capacitive Accelerometer, ” Sensors and Actuators A, Vol. 141, pp. 347 - 352, 2007.
[16] 李明儒，“ 靜電式微機電元件電容感測電路之設計、模擬與實現 ”，國立清華大學奈米工程與微系統研究所碩士論文，2008。
[17] R. R. Harrison and C. Charles, “A Low-Power Low-Noise CMOS Amplifier for Neural Recording Applications,” IEEE Journal of Solid-State Circuits, Vol. 38, no. 6, 2003
[18] Hastings Alan, “The art of analog layout,” Upper Saddle River, NJ : Pearson/Prentice Hall, 2006