ISFET传感器不稳定性的起因及其改善技术研究

Mechtnism of Strocturtl Instability of pH-ISFET and Techniqoes for Improvement

本文用实验证实了氮化硅敏感膜表面存在OH^-羟基和NH_2氨基团.指出了氢离子FET传感器不稳定的主要原因:敏感膜表面和溶液中羟基团的活跃性;被测溶液OH^-羟基因及其pH值随时间而变化,敏感膜固/液两相界面势的变化.还证实了氢离子敏FET传感器长期不稳定性与氮化硅敏感膜沉积工艺有关.通过调整或控制敏感膜表面或界面上羟基和氨基因及其比率,可以解决氢离子敏FET的长期稳定性.

There are three principal mechanisms confribuing to the instability of ISFET as follows: First, a series of experiments showed that hydroxyl most groups at she surface of Si3N4 film or in the electrolyte solution were active, subject to gain anh loss of electrons. Second, the stability of pH-sensitive FET varied with the depositiin conditicn in the fabrication process of ISFET. Third, the bulk effect of Si3N4 sensitive film caused a change in the interface potential drop across solid and liquid phases. Therefore, when the hydroxyl group substitution was large enough to produce a bulk effect, the interface potential drop had a corresponding ihcrease. We utilized the techniques of readjusting and controlling the ratio of hydroxyl groups to amine groups to enhance the stability of ISFET.