Laser Micro-Nano Patterning Based On Optical Dielectric Microsphere Array

Laser is a tool widely used in industrial manufacturing,which has the advantage of non-contact technology.It can be used to produce complex structures without photomask in air,vacuum or water.In addition,laser can be easily focused down to the micrometer scale,so it can be used in micro-device fabrication.In particular,it is widely used in marking,drilling,annealing,surface modification and other processes in the microelectronic industry.However,due to the diffraction limit,the minimum achievable resolution of a laser is limited by its wavelength.The microsphere provides a mechanism to manipulate light in a way that cannot be achieved by traditional optical components.The focusing and scattering of light can be manipulated at the microscopic scale by microsphere.Based on the near-field optics,the limitation caused by the diffraction limit is overcome.Therefore,people use optical dielectric microsphere to modulate the laser,and realize the micro-nano processing with the resolution above the diffraction limit.On this basis,people have also overcome the difficulties of traditional micro-nano processing technique,such as slow processing speed and unable to achieve large-area one-time processing,through the self-assembled microsphere array technology.At the same time,people also realize the processing of arbitrary micro nano patterns by off-axis laser irradiation technology.In this thesis,the micro-nano processing technique is used to realize the micronano processing by modulating the laser with the densely packed single-layer dielectric microsphere array.The pattern processing which breaks through the diffraction limit resolution is realized on the gold film on the surface of the microsphere.For this technology,the following research and work have been mainly done:The near-field optical enhancement effect of the microspheres was simulated and analyzed,and the mechanism of the effect of the laser direct writing technology on the gold micro-nano structure through the microsphere array was obtained.The optical field intensity of the microspheres was also simulated.The effects of the microsphere size and laser wavelength on the optical field enhancement and the FWHM of the laser peak were obtained.These theories and simulations lay the foundation for subsequent experiments.The micro-nano processing technique of microspheres by Mie scattering laser was studied.The process parameters such as laser wavelength,size of microspheres,thickness of ion sputtering coating,laser irradiation power density and laser off-axis irradiation offset angle were optimized.The morphological characteristics of gold micro-nano structure were characterized by scanning electron microscope,and the influence laws of each process on the processing results were summarized to optimize process parameters.The experimental results show that 100 nm diameter holes can be machined under the optimal process parameters.A dual-axial controller with angle rotation motors was developed.Through the controller,the laser irradiation angle required for processing any position can be obtained,which makes the laser angle deflection processing simple and efficient,so as to realize the patterned processing simply and quickly.Through the developed program system,the design and processing of arbitrary simple patterns are realized,and the resolution of the obtained gold micro-nano structures is close to the light diffraction limit.