Research On Nanolithographic Devices Based On Negative Refractive Metamaterials

As a key technology in the field of integrated circuits,lithography technology plays an extremely important role.Since the resolution of lithography technology directly determines the minimum size of the entire integrated circuit chip process.Surface plasmonic（SP）lithography can take advantage of SP resonance on the surface of metal-medium and participate in imaging with coupled evanescent wave,thus breaking the diffraction limit and becoming an effective super-resolution lithography technology,which has received wide attention.However,the rapid attenuation of evanescent wave in the propagation direction makes the pattern depth in photoresist very shallow.Negative refraction metamaterial is a new type of artificial electromagnetic material with negative refractive index,which can amplify evanescent waves to obtain subwavelength focusing,and the position of the focus can be changed by adjusting the thickness of the metamaterial.The surface plasmonic waveguide metamaterial composed of alternating metal and dielectric layers can realize the negative refractive index characteristics at high frequency.Based on the subwavelength imaging properties of evanescent wave and negative refractive index metamaterials enhanced by surface plasmon coupling,this paper uses surface plasmonic waveguide negative refractive index metamaterials to improve the working distance of lithography and increase the depth of focus of exposure patterns,which has important scientific significance and practical value.This paper mainly uses SP resonance coupling evanescent wave and negative refraction metamaterials to amplify the properties of evanescent wave and negative refraction imaging.Experiments and simulations are used to study the influence of metal-dielectric multilayer film negative refractive metamaterials on increasing the depth of focus and broadening the working distance of lithography,which has given a certain inspiration to the application of negative refractive index materials in lithography.The main content can be divided into three parts:In view of the fast attenuation of evanescent wave in plasmonic direct writing lithography,the beam is fast broadeningin the propagation direction,and the depth of photoresist（PR）is very shallow.In this paper,radially polarized light（TM polarized compared with concentric grating structure）is used to generate diffraction-free evanescent Bessel beam through metal-medium rings,so that the basic transverse shape of the beam remains unchanged in the propagation process.The hyperbolic dispersive negative refraction metamaterial with metal/dielectric multilayer dielectric constant approaching zero is used to efficiently transmit the graph information breaking the diffraction limit in high spatial frequency mode（1.62 k₀）,and the metal-PR-metal waveguide mode is combined to realize the Super-resolution lithography device with long focal depth.The simulation results show that the designed system can produce a needle-beam below diffraction limit and more than 400 nm（1.0λ₀）in the PR layer when the radial polarized light is incident at 405 nm,and the half-height full width of the beam only widths from 80 nm（0.2λ₀）to 94 nm（0.23λ₀）during the propagation.This design shows some advantages in the fabrication of nano-structures with various aspect ratios.The working distance of SP lithography is very short,and problems such as probe damage,tip wear and photoresist scratch will occur in large area scanning.In this paper,the 2D negative refractive index metamaterial properties of Metal-Dielectric-Metal（MDM）surface plasmonic waveguides are extended to 3D based on the SP antisymmetric mode.Compared with the 3D negative refraction achieved by the symmetric mode,the antisymmetric mode effectively reduces the Thickness of metal film.By adjusting the thickness of the metal-dielectric multilayer film to increase the working distance and increase the depth of the exposure pattern,a large-area photolithography pattern without side lobes was successfully achieved with only one exposure.The simulation and experimental results show that under the incident TM polarized light with a wavelength of 365 nm,large-area lithography with a working distance of 100 nm in air and a depth of focus of 160 nm can be achieved.Aiming at the problem that the evanescent wave decays exponentially in free space and the resolution of the optical field pattern decreases,a metal-dielectric-resist-metal resonant cavity mode is introduced to enhance the evanescent wave component in the optical field of the photoresist.Combined with the particle swarm optimization algorithm,which allows the thickness of the metal-dielectric layer to be different,and introduces additional degrees of freedom to further improve the resolution of the optical field,a negative-refractive metamaterial nanolithography device based on resonant cavity enhancement is proposed.The simulation results show that under the incident TM polarized light of 365 nm,the air working distance is 100 nm,the full width at half maximum of the isolated line is 118 nm,and the half period of the large-area dense line is 110 nm.When the filling medium is water,the full width at half maximum of the isolated line is 100 nm,and the half period of the large-area dense line is 90 nm.Compared with the waveguide mode and periodic film layer without the underlying reflective silver,the resolution of the pattern is improved to a certain extent.