The study of NafionTM/polymer structure based sensing films on pH-ISFET applications

• Main Authors: Jin-Li Chen, 陳敬岦
• Other Authors: Kow-Ming Chang
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/82386358087097339458

碩士 === 國立交通大學 === 電子工程系所 === 95 === 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. But the lack of a stable solid-state reference electrode is detrimental to the luring properties of ISFET. One approach to solve this problem is to use a differential measurement consisting of an ion-sensitive structure (ISFET) and an ion-insensitive structure (REFET). With this arrangement, the common mode unstable voltage generated from the thermodynamically undefined metal/ electrolyte interface can be eliminated. In this thesis, we first apply the Nafion mix PR(FH6400) structure to modify the ISFET sensing layer and successfully make the high H+ sensitivity ZrO2-pH-ISFET become a low H+ and Na+ sensitivity REFET. From the experimental results, the H+ sensitivity of ZrO2-pH-ISFET with the value of 57.89 mV/pH can be decreased to 5.8 mV/pH and Na+ sensitivity is also decreased from 15.88 mV/pNa to 11.27 mV/pNa. When in differential ISFET/REFET measurement, the H+ sensitivity and Na+ sensitivity will be 52.09 mV/pH and 4.61 mV/pNa, respectively. In order to realize the single ISFET integrated with a solid-state reference electrode, the simple and compact structure of ISFET sensor without the additional REFET or glass reference electrode, we also apply the Nafion mix PR structure for the solid-reference electrode. From the previous experimental results, we can know the Nafion mix PR structure can maintain a constant voltage for the sensing layer of REFET and prevent it from the ions disturbing. The experimental results show the troublesome and unstable problem can be greatly improved. Without REFET arrangement in differential measurement or replaced by glass reference electrode, the H+ sensitivity of single ZrO2-pH-ISFET integrated with solid-state reference electrode still can reach to 55.9 mV/pH and the output voltage is also very stable within 60 seconds.