| The development of science and technology has led to an increasing demand for integrated circuits and silicon-based optoelectronic devices,thus increasing the requirements for semiconductor manufacturing processes.In order to achieve large-scale device integration,processing processes at the nano scale have become a hot research topic.Characterization and optical defect detection of processed micro and nano structures is a crucial part of it.Optical microscopy can be applied to non-contact inspection and imaging detection techniques.However,the existence of diffraction limit limits the resolution of ordinary optical microscopes,with the highest resolution in the visible range at 200-300 nm,which cannot meet the requirements for imaging ultra-fine structures.Therefore,the use of super-resolution imaging technology in the field of materials to achieve high-precision characterization and detection of micro and nano structures is an important research topic.Silicon is a semiconductor material that is widely used in optoelectronic chips and nano optoelectronic devices.It is important to study the optical characterization of subwavelength feature size of nano silicon structures by means of fluorescence-free labeling.This thesis illustrates the mechanism of achieving lable-free super-resolution,using a grating-shaped silicon with a linewidth of 100 nm and a pitch of 150 nm as the core,and shows the results of achieving super-resolution with a confocal optical path,as well as the application to other structures.The following innovative results were accomplished in this thesis.1.Based on scanning reflectance confocal microscopy,the variation of point spread function(PSF)with incident optical power for line structures with linewidth of 100 nm pitch of150 nm irradiated by a 532 nm continuous laser was studied,and the phenomenon of super-resolution localization based on the photothermal nonlinear reflection principle was systematically recorded and analyzed.The resolution of scanning imaging was significantly improved by gradually increasing the incident optical power under the oil-immersion objective.Meanwhile,the line structure system embodies different nonlinear reflection responses for different polarization excitations of the incident light,which are reflected in the experiments as different reflection imaging results.The experimental optical path used is simple,no fluorescence labeling of the sample is required during the experiment,and the super-resolution localization results can be obtained without complicated processing of the experimental results after the experiment.2.The reflectance spectrum of a grating structure with a line width of 100 nm and a pitch of150 nm is simulated and the actual reflectance spectrum is experimentally tested to verify the accuracy of the simulation results.Combined with the simulation results,theoretical calculations are performed to explain the principle that periodic silicon line structures can achieve super-resolution,and the reasons why different nonlinear behaviors(linear,sublinear and super-linear)correspond to different scanning imaging results.3.To further reduce the introduction of other substances,we directly scan and image grating structures of different sizes with an air mirror.The imaging results of several other sets of periodic silicon line structures of different sizes and pitches with different polarization directions at low and high power are shown and analyzed.There is a significant improvement in the resolution at high power in all cases.It is shown that the method is highly generalizable,demonstrating the potential of densely arranged structures in the diffraction limit to achieve lable-free super-resolution localization.4.In order to show the universality of this super-resolution technique,the experiments are performed on silicon structures prepared by different methods with different morphologies,such as silicon disk arrays with diameter of 200 nm and height of 60 nm,ultraviolet lithography processed metalenses,and electron beam lithography nanochip(the structure has different shapes such as folds,circles,and curves).The experimental results show that the silicon based photothermal nonlinearity can be imaged super-resolution without labeling using scanning confocal microscopy,and the method can be used to characterize micro-nano silicon structures made by different morphologies and processes. |
