以薄膜擠壓效應為基礎之0.18μm CMOS電容式微機電壓力感測器開發

Development of Squeeze-film Based 0.18μm CMOS MEMS Capacitive Pressure Sensors

李諺儒(Yen-Ju Lee)

指導教授 ： 盧向成

國立清華大學/電機資訊學院/電機工程學系所/碩士(2021年)

摘要

本論文使用薄膜擠壓效應(Squeeze-film damping effect)之特性應用於氣壓感測，不同於傳統的壓力感測器需要封閉性的空腔作為氣壓基準，在此效應中，透過上下平板間的高頻振動產生空氣彈簧力與阻尼力來感測氣壓變化。
本感測晶片使用TSMC 1P6M 0.18μm CMOS製程，並透過硫酸濕蝕刻、反應離子蝕刻等後製程步驟成功釋放結構，結構分為上下電極，上電極為厚度3.131μm之振動結構用於電容式感測，下電極為固定電極用於靜電式驅動以及電容式感測，並與感測電路整合於單一晶片上，晶片的面積大小為1.3 mm x 1 mm。本研究設計五種不同平板面積、彈力係數的壓力感測器，透過電容式感測得知共振頻隨壓力之變化，量測每個結構對氣壓的感測度，並與模擬結果做比較。舉其中一感測元件為例，其模擬感測度能達到8.51 Hz/Pa，量測結果為4.03 Hz/Pa。
此外，本研究透過增益及相位補償，成功使晶片在20 kPa環境氣壓下並且無須外加交流訊號，即可自行輸出週期性波形，形成震盪器，其振幅超過電源供應器提供的1.8 V，而其共振頻率為666 kHz。

關鍵字

薄膜擠壓阻尼效應 ； 電容式壓力感測器 ； 震盪器

並列摘要

The purpose of this thesis is to investigate the application of squeeze-film damping effect for pressure sensing. Different from traditional pressure sensor, squeeze-film pressure sensor doesn’t require a sealed space as reference to monitor ambient pressure. It uses a vibrating plate with high speed to trap air in gap between two plate. The detection ambient pressure is based on the induced air damping force and air spring force.
This sensor chip is fabricated using TSMC 1P6M 0.18μm CMOS process. The structure is released by wet etching followed by dielectric reactive ion etching. The sensing structure can be separated by two part. One is top movable plate with 3.131 μm thickness used for capacitive sensing and the other is the fixed bottom plate used for both capacitive sensing and driving signal. The chip size is 1.3mm x 1mm. There is five different pressure sensor design with various plate sizes and spring constant in this paper. The resonant frequency of each design is measured and the sensitivity with aspect to different pressure is compared to the simulation result. For instance, one of five design has a simulated sensitivity of 8.51 Hz/Pa, but its measured sensitivity is only 4.03 Hz/Pa.
Furthermore, in this study, the resonant sensor is connected as an oscillator to generate periodic waveform at 666kHz after gain and phase compensation.

並列關鍵字

Squeeze-film damping effect ； Capacitive sensing pressure sensor ； Oscillator

參考文獻

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