CMOS電容式流量感測器之設計與製作

這項研究提出一種用於人體呼吸流量的微感測器，可對於呼吸疾病患者做長時間的監測與觀察。透過CMOS MEMS的技術將感測結構與電路整合在單晶片上，相較於傳統MEMS所用的多晶片整合，可有效降低外接線路所帶來的寄生效應；而且在體積上也可大幅縮小，一方面可以降低成本，另一方面可提高模組化的整合性。本研究目的在於感測呼吸的訊號，所以在晶片的感測微結構使用了三層極板的設計，製作出差分式感測電容，使其能夠增加呼吸流量的感測訊號。本晶片使用 TSMC 0.35μm 2P4M 標準製程定義電路與微結構，透過後製程將犧牲金屬層(Metal1與Metal3)蝕刻掉以釋放出面積為 320μm × 230μm 的感測薄膜結構，並具有 124fF的差分感測電容。本晶片總面積為 2.46×2.46 mm^2。工作電壓為5V，電流消耗為5mA。本實驗結果已經量測出連續的呼吸訊號，並且經由空氣幫浦做定流量的量測後，可操作在流量0~6 L⁄min的範圍內，感測度為3.33mV/(L/min)，並且經由換算可知感測解析度為 34.4(mL⁄min)。

關鍵字

電容式；流量感測；呼吸

並列摘要

The research studies a capacitive micro-sensor used for long-term respiratory monitoring of patients with breathing difficulties. By using CMOS-MEMS technology, we can integrate sensing structures and circuits into one chip. Parasitic effect is therefore reduced to enhance the signal-to-noise ratio. The chip size and fabrication cost are reduced as well. The capacitive flow sensor is fabricated by using the TSMC 0.35-μm 2P4M (two-polysilicon-four-metal) CMOS process. The differential sensing capacitances are formed by the metallization and polysilicon layers. Capacitance change is produced by momentum change of the air flow on the microstructure, which is released by wet-etching of metal-1 and metal-3. The sensor area is 320μm × 230μm. The sensing capacitances are about 124 fF. The total chip area is 2.46 × 2.46 mm^2. The sensing circuit is operated at 5 V with a total current consumption of 5 mA. The measured data shows the sensor has a sensitivity of 3.33 mV/(L⁄min) and a detection limit of 34.4 (mL/min) within a 1-Hz bandwidth. We have successfully measured the waveform from a subject’s nasal respiration.

並列關鍵字

CMOS ； MEMS ； Capacitive ； Flow sensor ； breathing

參考文獻

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CMOS電容式流量感測器之設計與製作

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