Design And Optimization Of Field Effect Transistor Biosensors

As the basic unit of micro electronic integrated circuit, Field Effect Transistor (FET) possesses the characteristics of well-developed fabrication process and simple structure. It is as early as 60th last century that the Field Effect Transistor has been used to sense biomolecules. Since the advantages of mass-production and low cost, industry also takes a great interest in FET biosensor. Furthermore, the output impedance of FET is very low, and the line linking FET biosensor and testing circuit does not need to be shielded, which simplifies the design of testing circuit. More importantly, many FET biosensors can be integrated in a single silicon chip, which provides real time detection of many objects at the same time. Supported by the National Science Foundation of China, the theoretical model and sensitivity are systematically studied in this thesis, as well as the preparation of bio- recognition part. The main contents are listed as follows:(1) The working principle of FET is thoroughly investigated, especially charge distribution, FET capacitances and band structure in subthreshold working condition, based on solid state physics theory and statics electrical field theory. Theoretical model is established, from which expressions of key parameters and working condition are derived.(2) Modified the structure of traditional FET by inducing control and reference mechanisms to improve the stability and selectivity of FET biosensor. Analyzed the effects of control and reference mechanisms imposed on its working condition and electrical characteristics, based on finite element analysis.(3) Preparing bio- recognition film—immobilize biomolecules on sensing chip. Both physical adsorption and covalent bonding methods have been tried, and fluorescent scanner and atomic force microscope were used to measure the quality of immobilization. Finally, we did DNA hybridization experiment, and used color reaction to test it.