Modeling and discussion of threshold voltage for a multi-floating gate FET pH sensor

Research into new pH sensors fabricated by the standard CMOS process is currently a hot topic. The new pH sensing multi-floating gate field effect transistor is found to have a very large threshold voltage, which is different from the normal ion-sensitive field effect transistor. After analyzing all the interface layers of the structure, a new sensitive model based on the Gauss theorem and the charge neutrality principle is created in this paper. According to the model, the charge trapped on the multi-floating gate during the process and the thickness of the sensitive layer are the main causes of the large threshold voltage. From this model, it is also found that removing the charge on the multi-floating gate is an effective way to decrease the threshold voltage. The test results for three different standard pH buffer solutions show the correctness of the model and point the way to solve the large threshold problem.     

基于标准CMOS工艺的pH值传感器

基于传统离子敏感器件的敏感模型,建立了与CMOS工艺兼容的以钝化层氮化硅作为敏感膜的MFGFET(multi-floating gate FET)多层浮栅晶体管结构阈值电压模型.采用上华0.6μm CMOS标准工艺,设计了一种与CMOS工艺兼容的pH值传感器.片上控制电路使MFGFET器件源漏电压和源漏电流恒定,器件工作在一个稳定的状态.采用离子敏MFGFET和参考MFGFET差分拓扑结构,减少了测量电路的固定模式噪声.器件溶液实测pH值在1～13范围内,器件的平均灵敏度为35.8mV/pH.     

多层浮栅FET pH传感单元阈值电压敏感模型分析和讨论

Research into new pH sensors fabricated by the standard CMOS process is currently a hot topic. The new pH sensing multi-floating gate field effect transistor is found to have a very large threshold voltage, which is different from the normal ion-sensitive field effect transistor. After analyzing all the interface layers of the structure, a new sensitive model based on the Gauss theorem and the charge neutrality principle is created in this paper. According to the model, the charge trapped on the multi-floating gate during the process and the thickness of the sensitive layer are the main causes of the large threshold voltage. From this model, it is also found that removing the charge on the multi-floating gate is an effective way to decrease the threshold voltage. The test results for three different standard pH buffer solutions show the correctness of the model and point the way to solve the large threshold problem.