以Polyimide高分子材料/NafionTM質子交換膜為結構作為pH-ISFET之微小化固態電極之研究

Abstract

離子感測場效電晶體( Ion-sensitive Field Effect Transistor )是由Bergveld在1970年首先提出，由於它的尺寸小，反應速度快、可承受外部應力，且與現今的CMOS製程相容，所以在現在的感測元件開發中具有相當大的潛力。 但是由於缺乏一個穩定且微小化的固態參考電極，使得ISFET的應用受到很大的限制。為了要實現一個最簡單且小型結構的ISFET，在微小化的技術上，必須要整合一個固態參考電極在單一ISFET晶片上，不需要額外再使用到REFET或玻璃電極。 從過去的實驗結果可知道，NafionTM混合Polymer的結構具有使REFET的感測層維持在一個固定的電位且保護它不受離子的干擾的效果。在本篇論文中，我們成功地以Polyimide/ NafionTM的結構應用到固態參考電極的表面修飾上，使得固態參考電極因為金屬/溶液接面產生的不穩定電壓被消除。由實驗結果可看出，令人困擾的電壓不穩問題，大幅地獲得改善。一個單一的ISFET整合固態參考電極在不需搭配REFET或玻璃參考電極的情況下，對氫離子的靈敏度可達到56.5 mV/pH而且輸出電壓也展現相當優秀的重線性及線性度，且對鈉離子的靈敏度只有7.5 mV/pNa的低靈敏度。以Polyimide/ NafionTM塗佈的固態電極作為參考電極，在24小時下的量測結果顯示，飄移速率更可達到每小時1.05 mV的低程度飄移率。

ISFET( Ion-sensitive Field Effect Transistor ) was first developed by Bergveld in 1970s, and because of its small size, fast response, rigidity and compatibility with standard CMOS process, ISFET is an attractive candidate of modern sensor device. Due to the lack of a stable and miniaturized solid-state reference electrode, the applications of ISFET will be restricted seriously. In order to realize the single ISFET integrated with the simple and compact structure solid-state reference electrode by miniaturized technology, the simple and compact structure of ISFET sensor was fabricated without the additional REFET or glass reference electrode. From the previous experimental results, we can know the NafionTM mix PR structure can maintain a constant voltage for the sensing layer of REFET and prevent it from the disturbance of ions. In this thesis, we successfully apply the Polyimide/ NafionTM structure to modify the surface of the solid-state reference electrode. The unstable voltage generated from the thermodynamically undefined metal/electrolyte interface can be eliminated. From the experimental results, it is obviously that the troublesome and unstable problem can be greatly improved. Without REFET arrangement in differential measurement or glass reference electrode, the H+ sensitivity of single ZrO2-pH-ISFET integrated with solid-state reference electrode still can reach to 56.5 mV/pH and the output voltage also exhibit high reproducibility and linearity. Furthermore, the Na+ sensitivity can reduce to 7.5 mV/pNa. During a measurement period of 24 hours, the reference electrode with Polyimide/Nafion coating shows a low averaged drift rate of 1.05mV/h.