CMOS-MEMS純金屬電極觸覺型電容式壓力感測器

Abstract

本研究嘗試設計以金屬為主體的薄膜結構，製作電容式壓力感測器，以應用於體外非侵入式血液流感測器，利用商用製程TSMC CMOS MEMS 0.35μm 2P4M下線平台下線，搭配商用氧化矽蝕刻劑Silox Vapox III以及自行開發的後製程步驟。其優點可增加電極間的有效移動空間。且為減少直接量測電容而產生的寄生效應，後端搭配方波震盪電路；本論文感測器實作可分為兩代設計，第一代是提出垂直梳狀電極的想法，跟傳統平板電極做個比較，但發現該設計會有翹曲與容易短路等不理想效應；第二代共八種設計，加入防短路措施於平板電極中，以及比較不同幾何參數的設計效應，尤其在這篇論文提Via金屬連結層的三種設計，分別為點狀、網狀跟散狀，利用幾何結構的不同，成功的調變結構的力學參數，藉此提高其靈敏度，以及減少翹曲效應的發生，靈敏度從1.23~5.37Hz/ mmHg，最大可量測範圍晶片高達618mmHg。

In this research, CMOS MEMS tactile sensors using a pure metal-based structure to monitor non-invasive blood flow were developed. The sensors were fabricated through a commercial 0.35μm 2 polysilicon and 4 metal CMOS technology by the self-developed post processes. In order to increase the effective gap between two electrodes, the tactile sensor used oxide as the sacrificial layer to replace the conventional metal sacrificial layer. Moreover, to eliminate parasitic effect, the change of capacitances is measured and analyzed via an oscillator circuit which converts the capacitance output to the frequency output. Many sensor designs were proposed and developed in this work. First, a vertical-comb-drive type sensor and a conventional parallel-plate type sensor were proposed. Due to some problems encountered in the experiment such as the curling effect and device shortage problem, various modifications were made to improve the device performances, To adjust the mechanical strength of the membrane of the sensor, three via designs were proposed including designs of point-shape, net-shape, and ring-shape. Moreover, we also designed various microstructures for short-prevention mechanism of the tactile sensor. Finally, the maximum sensitivity of 5.37Hz/mmHg and a maximum sensing range of 618mmHg were demonstrated successfully.