Research On A Silicon-based Biosensor Compatible With CMOS Process

Technology has changed life.Ordinary sensors will not be able to adapt to the intelligent era of interconnection of all things due to non-intelligence and other reasons.The smart era puts forward higher requirements for sensors,so smart sensors come into people's field of vision.The smart era requires more portable and efficient smart sensors,and the smart era places higher requirements on the internal integrated circuits of smart sensors.Because optical interconnection technology can make smart sensors miniaturized,precise,and efficient,optical interconnection technology will become a research focus in the field of integrated circuits.Monolithic integration is another condition for miniaturization and high efficiency of smart sensors.The current integration processes mostly use standard complementary metal oxide semiconductor(CMOS)integration processes,and monolithic integration requires that each component is compatible with standard CMOS processes.The on-chip all-silicon photoelectric biosensor is composed of a silicon-based light source,a silicon optical waveguide,a photodetector,and a back-end processing circuit.Each component is compatible with standard CMOS processes.Silicon is an indirect bandgap semiconductor.This structural feature of silicon makes high-efficiency silicon-based light-emitting devices and high-transmission-efficiency silicon optical waveguides difficult to design and manufacture.The sensitivity of sensors equipped with ordinary silicon-based light-emitting devices and ordinary silicon optical waveguides is not high.Therefore,manufacturing high-efficiency silicon-based light-emitting devices and high-efficiency waveguides is the focus and difficulty in the field of on-chip miniature all-silicon photoelectric biosensors.This article mainly focuses on the on-chip miniature all-silicon photoelectric biosensor technology.Starting from the structure of the light-emitting device,the light-emitting mechanism,the transmission efficiency of the waveguide and the detection mechanism of the sensor,the light source of a polysilicon cascade structure and a combination of silicon dioxide and nitrogen Research on the advantages of silicon(Si₃N₄)in the optical waveguide structure and the principle of evanescent wave.The silicon-based light source is a polysilicon PN junction cascade light-emitting device with an N⁺PN⁺PN⁺structure,and the device is reversely avalanche breakdown to emit light by applying a reverse bias voltage.The silicon-based light source adopts carrier injection technology to improve the luminous efficiency,and the luminous efficiency is as high as 4.3×10^-6,which can be coupled with the waveguide.The spectrum of the silicon-based light source is a continuous spectrum,and the wavelength range is400-900 nm.The waveguide structure uses the advantages of silicon dioxide and Si₃N₄to meet the low loss requirements of optical transmission and solve the bottleneck of the bandwidth limitation of the optical transmission and CMOS process integration technology in the visible light band.The waveguide sensor has a thin sensing layer,which is helpful for rapid response and high-sensitivity detection of molecules.Through the simulation of straight waveguides,it is found that the waveguides with the model length,width,and height of 40?m,6?m,and 6?m have the best waveguide transmission effect at the best light source incident angle(32.8°),and the average transmission efficiency is as high as 95%.The average sensitivity is:every time the refractive index increases by 0.1,the relative light wave intensity changes by 5%.From the results of waveguide simulation,it is concluded that the light wave energy of the inner core of the waveguide decreases with the increase of the refractive index analyzed in the detection area,and the curve presents a monotonicity.Realizing the sensing of the refractive index of the medium through the change of light wave energy shows the feasibility of the evanescent wave detection mechanism in the all-silicon photoelectric biosensor,and lays a solid foundation for the realization of high-efficiency all-silicon photoelectric biosensor.