基于磁通门信号检测机制的光寻址电位传感器研究

An electric charge gate theory is proposed based on the saturation excitation on voltage axis, using the fluxgate signal detection mechanism for reference. The theory is used to solve the problems of the Light-Addressable Potentiometric Sensor (LAPS), which is difficult to improve the accuracy and measuring speed concurrently. By introducing a saturation excitation, the accuracy and measuring speed will be improved，as the photocurrent is controlled by the two gates generated in the cut-off region and saturation region. The LAPS mathematical models and SPICE models will be built using the methods of mathematical fitting function optimization and large number of experimental data comparison. After optimum design and selection among the four signal detection methods evolved from the electric charge gate theory, the two optimum design schemes will be selected out for low cost and high accuracy applications by the methods of circuit simulation and experiments. A Direct current illumination design scheme is proposed based on the electric charge gate theory to solve the mutual modulation problem between the voltage excitation and light illumination and improve measuring speed concurrently. By optimizing the technologies of the silicon and germanium semiconductor substrate material and the insulating layer on the substrate, the influence to the performance of the LAPS by the substrate material, insulating layer and fabrication technologies will be studied and the working mechanism of the electric charge gate LAPS will be explained. The research results will provide a new signal detection theory for biochemical sensors based on the principle of semiconductor field effect.

针对传统光寻址电位传感器（LAPS）精度和速度很难同时提高的问题，借鉴磁通门信号检测机制，本项目提出在偏置电压轴施加饱和激励的检测理论——电荷门理论，通过引入饱和激励，使光电流受到截止区与饱和区形成的两个门的作用，提高检测精度和速度。采用优化数学拟合函数与大量实验数据对比的方法，建立基于电荷门理论的LAPS数学模型和SPICE模型；采用电路仿真分析和实验的方法，对基于电荷门理论演变出的四种信号检测方法进行优化设计与选择，最终获得分别针对低成本和高精度应用的两种最佳方案。提出基于电荷门理论的直流光照射LAPS方案，解决电压激励与光激励的相互调制问题，同时提高检测速度。通过对硅和锗两种半导体基片材料的工艺优化及基片上绝缘层的优化，研究基片材料、绝缘层和制备工艺对LAPS性能的影响，解释电荷门LAPS的工作机理。以上研究成果将为半导体场效应原理的生化传感器提供新的信号检测理论。

针对传统光寻址电位传感器（LAPS）速度和精度很难同时提高的问题，提出了一种电荷门理论，把进入反型区和积累区时光电流保持不变的现象描述为LAPS中有两个控制着电荷（光生载流子）运动的门，反型区门和积累区门。基于该理论，引入幅度足够大的交流电压激励使传感器的半导体基片周期性地进入反型区、耗尽区和积累区，构建了一种处理电路由选频跨阻放大器、解调器、最大值电路、最小值电路和平均值电路构成的新型LAPS系统结构。建立了被测量在敏感膜上形成的能斯特电势与系统输出信号间的数学关系，并据此总结出了提高检测灵敏度的方法。这种想法使我们提出了一种新型检测机制的电解质-绝缘体-半导体电容器型传感器，称为饱和激励EISCAP传感器。为了改善传感器基片材料性能，将一种低成本聚苯乙烯（PS）胶体球光刻工艺引入LAPS基片材料的制备过程。基于这种工艺研究了三种改善LAPS传感器性能的方法。在传感器基片上制备微纳米结构的蜂巢网状工作电极使LAPS获得很高的空间分辨力；在基片上刻蚀出有序倒金字塔坑形图案，可以改善光照效率提高LAPS的信号幅度和信噪比；在基片上制备PS胶体球制成的微透镜阵列，可以提高LAPS的最佳光照频率。采用固态参考单元构建了差分型LAPS传感器，避免了在长期使用过程中参考单元的敏感膜易受污染而使用寿命降低的问题。探索了正交相位检波的正交相位闭环LAPS检测方法和基于单层二流化钼的场效应管的无参比电极检测方法。研制了检测pH值、尿素和和核酸的传感器原理样机。本项目提出的电荷门理论和新型LAPS系统结构，为进一步研究基于饱和电压激励型LAPS传感器奠定了理论基础。