本論文目的在於探討如何以微結構懸臂樑來達到量測液體之黏滯度與密度，其驅動的方式是透過晶片下面的壓電片振動而來，為了能夠感測微懸臂樑的振動行為，結構的感測方式則是運用多晶矽材料的壓阻感測器沉積在微懸臂樑固定端之中，以利電訊號傳遞以及回授的振盪電路。
本晶片使用TSMC 2P4M 0.35 m CMOS製程，將壓電式微懸臂樑結構、感測電路整合於單一個晶片上，晶片總面積為2.8 mm × 2.8 mm，利用CMOS製程將氧化層及多晶矽層當作振動結構的質量塊，將微懸臂樑設計不同長度、寬度及厚度來比較感測度，其中較寬的結構可以得到較高的量測品質因素，晶片結構的共振模態由壓電片z軸垂直振動的驅動而來，其振動的位移可由外加的交流電壓大小來改變，可避免較大的電壓或電流驅動導致結構或是晶片電路的損壞，最後以簡單、低成本的方式開發一套完整的後製程。
完成製程後，微懸臂樑結構量測的結果，空氣共振頻率測得為9.29 kHz，模擬則為10.21 kHz，其誤差原因是製程後導致微懸臂樑厚度變薄，另外在純水溶液之共振頻率為2.62 kHz、品質因素為1.75，透過這些量測數值可以間接推得該液體的黏滯度為0.90 cp、密度為768.2 kg/m3，與參考值之黏滯度為1.002 cp、密度為998.2 kg/m3甚為接近。結構驅動部分採用壓電片材料，將晶片黏著於壓電片上並外接網路分析儀與高壓放大器產生交流電壓驅動之，壓電片與晶片的振動位移和頻率可由網路分析儀或是訊號產生器來做及時的調整。感測電路部分使用壓阻感測器與電壓緩衝器作為感測訊號的接收方式，再經過補償電路，確認開迴路增益與相位符合巴克豪森準則，最後成功將空氣共振頻率達到穩定的振盪。

A thesis proposes a method for measuring viscosity and density of fluids using microcantilever beam on chip. Microcantilever are made of silicon oxide and driven by a piezoelectric actuator. In order to monitor microcantilever resonant frequency, polycrystalline silicon deposited on the anchor of microcantilever is used to provide piezoresistive sensing of the motion.
The integrated chip containing the mechanical structure, sensing and buffer circuit, is implemented by using the TSMC 2P4M 0.35μm CMOS process. The chip area is 2.8 × 2.8 mm2. We use oxide and polycrystalline silicon layer of CMOS process as proof mass and design structures of different lengths, widths and thicknesses to compare the sensing performance. The wider structure can obtain higher quality factor from the measurement. The piezoelectric sheet will provide z-axis oscillation mode to drive microcantilever and the vibration displacement can be adjusted by changing AC voltage. Therefore, we can avoid damage to the chip or structure when using larger driving voltage or current. Finally, we develop a convenient and low-cost post fabrication process and successfully fabricate the microcantilever beam device.
The fabricated microcantilever structure shows the measured and simulated resonant frequencies at 9.29 kHz and 10.21 kHz, respectively. The difference is due to the post fabrication process, that causes structure to become thinner. The measured resonant frequency and quality factor are 2.62 kHz and 1.75, respectively, for DI water. Through above measurement, we can indirectly obtain the viscosity and density of liquid. Besides sensing circuit on chip, we also set up external compensation circuit to make the system oscillate in the air.

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