Modal Analysis Of Nanoscale Bowtie Antenna And Application In Nanolithography

Lithography has long been a"neck clamp" technology for nanoscale manufacturing,especially in the semiconductor industry.It has made great progress in the past few decades,and been successful in promoting the development of nanotechnology.However,the diffractive nature of light has grratly limited the continuous advance of optical lithography resolution in visible band.In the actual lithography process,in order to overcome the optical diffraction limit,phase shift masks,off-axis illumination,optical proximity effect correction and other technologies are generally used.But the corresponding processes are relatively complex Therefore,it is extremely urgent to realize high resolution and high flux lithography in high efficiency and low cost.In recent years,the high self-assembly lithography,nano/microsphere lithography,plate interference lithography and nano-imprint lithography developed have achieved good results.Near field scanning optical lithography(NSOL)using nano ridge apertures has attracted much attention.Through the research and development of this technology,the combination of electronics and photonics in nanoscale can be realized,which is expected to develop into a new generation of photo-electric technology,and has potential applications in high-density data storage,bio-sensing,efficient energy acquisition and other fields.Near field scanning optical lithography can process a series of graphics on photoresist in high resolution and in parallel.At present,the generally accepted theory about the physical mechanism of near-field enhancement is that affected by the incident light,surface plasmon resonance occurs between the metal and the medium,which leads to the enhancement of the light in the sub-wavelength area.This kind of local field enhancement behavior has broken through the traditional diffraction optical limit,which enables the realization of optical frequency nano antenna,bowtie nano antenna has been popularized by many researchers.In this paper,the bowtie antenna is regarded as a waveguide structure.Based on the basic theory of waveguide,its electromagnetic transmission response under different incident excitation,different structure and different materials is analyzed,and its near-field behavior is further studied.The existence of Fabry-Perot resonances in each waveguide mode is determined by this novel analysis method,which together affect the transmission characteristics of the structure.Furthermore,we propose hybrid coupling phenomena between waveguide modes and surface plasmon polarion modes,such as TE10/WPP,TE30/CPP waveguide hybridized plasmonic modes.The effects of these phenomena also give us a new understanding of near-field enhancement.Furthermore,the control of these two indexes is extremely important during lithography.One is line width;another is working distance.With the feature size of semiconductor technology getting smaller and smaller,the requirement of line width and working distance is getting higher and higher.1?For line-width,it is necessary to use the near field scanning lithography to enhance the ridge nano apertures.However,the size of the ridge aperture is generally in the order of hundreds of nanometers,and the size of the specific area is even close to several nanometers.The structure size determines the near field enhancement of the bowtie aperture.This requires a very high level of nano processing.A highly confined electric near field is produced by localized surface plasmon excitation and nanofocusing of the closely tapered gap.Therefore,the successful manufacture of a bowtie antenna with a suitable structure is very important for the line width of near-field lithography.This also led us to propose a new template processing method,"back processing"method,for the preparation of small gap bow antenna structure.2?For working distance,because the energy of the light field in the near field area exponential rapidly in the far field,the effective working distance of the system is usually less than 50nm,and the mask and the substrate are in close contact in the lithography process.This restriction also makes alignment in the experimental process more difficult.On the other hand,the line width of near field lithography is only 20-50nm,which also requires that the template should not show significant displacement during scanning.Considering the above requirements,we propose a passive flexible stage suitable for near field lithography system.flexure hinge with a high off-axisstiffness is the fundamental unit of the stage,which incorporates a circular cutout on either side of the blank.To maintain orientation motion between the mask and the substrate with a low load,two layers of hinges are designed with eight hinges in each layer.It realizes the alignment requirement in near-field lithography.The two technical difficulties and problems above have been well solved in this paper.These work optimizes the experimental scheme of near field lithography and further improve the resolution of the near field lithography system,13 nm for static lithography and 22 nm for scaning lithography.