Super-Resolution Interference Lithography Based on Dielectric Waveguide Coupling
Objective China's semiconductor industry is an important part of the global industrial chain,contributing to its strength in global technological progress and economic development.With technological improvements,the chip size requirements in the semiconductor industry are becoming increasingly stringent,and the degree of integration of chip preparation is increasing.Among the many links in semiconductor chip technology,lithography is the most refined.However,lithography technology is constrained by the optical diffraction limit,resulting in many problems with improving the resolution.Therefore,breaking through the diffraction limit is an important research direction for many research teams,and new super-resolution lithography technologies are rapidly being developed.However,near-field lithography,which improves the resolution by collecting evanescent waves,is the most direct and effective method for obtaining super-resolution patterns.However,current lithographic devices that manipulate evanescent waves need to resolve critical problems,such as inherent metal loss,complex multilayer film design,and low transmission efficiency.Therefore,investigating new evanescent wave control methods and designing super-resolution lithography devices with low structural complexities and high transmission efficiencies can significantly promote the development and progress of near-field super-resolution lithography.In this context,we propose super-resolution interference lithography based on dielectric waveguide coupling.Methods By selecting appropriate materials and film thicknesses,a special waveguide that presents a narrow passband in the optical transfer function(OTF)curve can be formed.During the propagation of light waves in waveguides,diffraction waves of specific orders are coupled and emitted along the transmission direction,owing to the frequency-selective transmission function of waveguides.By constructing an asymmetric waveguide,only high k diffracted waves located in the passband can pass through efficiently.If the waveguide core layer is designed as a grating structure,it performs a basic diffraction function,and if the wave vector magnitudekgof the diffracted light matches the waveguide mode,the light can be effectively transmitted in the waveguide structure.Therefore,the period and duty cycle of the grating can be optimized based on the OTF characteristics.Based on this,if a beam of TM linearly polarized light is vertically incident on the surface of the grating from the top SiO2 substrate,it will excite a series of diffracted lights of different orders.Under the mode selection function and coupling transmission of the double waveguide structure,a pair of diffracted light beams of the same order can be filtered out,and a uniform super-resolution lithography pattern can be formed in the PR layer,owing to the interference effect.Results and Discussions We propose a novel super-resolution interference lithography method based on the coupled theory of dielectric waveguides.This method achieves enhanced transmission and interference control of evanescent waves by constructing asymmetric waveguides.By selecting reasonable waveguide gaps,optimizing the design of dielectric gratings,and utilizing waveguide coupling effects,the±1st diffracted light excited by the grating can be effectively transmitted in the dielectric waveguide structure.The energy of the optical field is mainly concentrated in the PR layer and thereby achieves an efficient waveguide coupling effect.The pattern period formed by the interference is half of the mask grating period,and the interference pattern penetrates the entire PR layer.The simulation results(Fig.3)show that the super-resolution interference patterns exhibit high field intensity and good uniformity.The two-dimensional light field image captured from the middle position of the PR layer shows that the feature size of the interference patterns is approximately 48.75 nm(approximately 0.12λ)and that the average peak light intensity is approximately 14.3 times that of the incident light.Calculations show that the contrast of the interference patterns is approximately 1.Higher light intensity and contrast are beneficial for improving the exposure efficiency and performance stability in practical applications.Conclusions This method is based on the principle of dielectric waveguide coupling,which achieves enhanced transmission and interference control of high-frequency evanescent waves.The designed device has a simple structure and simultaneously avoids complex multilayer film design.The all dielectric structure can also avoid the possibility of introducing metal impurity particles,improve the light utilization efficiency,and enhance the reliability of actual experiments.This method provides new ideas for super-resolution lithography technology and evanescent wave control,expands the design principles of super-resolution lithography devices,and has broad application prospects in nanomanufacturing.
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