Principle And Methodological Investigation On Super Resolution Interference Lithography Based On Surface Plasmons

Due to the novel optical properties,micro-/nano-structures have been widely applied in nano-photoelectrons.Suffering the diffraction limit,the resolution of conventional laser interference lithography approach utilized in micro-nano structures fabrication could not surpass one fourth of the wavelength.This problem could be resolved by employing light source with shorter wavelength,but the expensive sources limit the applications of this lithography method.Surface plasmons?SPs?,as one kind of subdiffraction electromagnetic mode,its propagation wavelength is much smaller than that of photons with same frequency in vacuum.As a result,the period of SP interference fringe would much shorter than that of the laser interference fringe,so the resolution of the SP interference lithography would achieve to dimension smaller than one hundred nanometers,and even the lithography node of 32 nm.This method provides the comparatively cheap fabrication solution for micro-/nano-optoelectronic functional devices.In this dissertation,the super-diffraction property of surface plasmon waves are used to develop the principle and experimental research of deep sub-wavelength interference lithography with super-resolution.The content is mainly composed of three parts.Firstly,period reduction BPPs interference lithography based on Al/SiO₂multifilms;secondly,deep subwavelength interference lithography with tunable pattern period were proposed is designed and verified;thirdly,deep subwavelength SPs interference lithography with separated structure is proposed and experimental verified.The detailed contents and results is presented as following:1.We investigate the period reduction BPPs interference lithography based on hyperbolic metamaterial?HMM?.The HMM,consisting of alternative Al/SiO₂ films,shows filter property,which enables selecting waves with given wavesvector.The diffraction orders excited by the grating that satisfying the wave mismatch can pass through the dispersive material and form a large-area,periodic deep sub-wavelength interference pattern in the photoresist.In order to improve the interference field intensity,the dielectric grating and the back reflection technique were introduced.In addition,we analyzed the factors that affecting the uniformity of the interference pattern in the photoresist.This method was applied to achieve 20 mm×20 mm and uniform periodic subwavelength lines with a half-period?35nm?about?/10.Varied periodic interference patterns were also simulated.This lithography promotes the development of near-field super-resolution interference lithography,and has potential application value in the preparation of large-area,periodic micro-nano structures.2.Deep subwavelength interference lithography with tunable pattern period based on BPPs.Conventional interference lithography has the advantage in forming interference patterns with tunable period,but the period resolution is only 1/4wavelength,which limited by the diffraction limit.Interference lithography based on surface plasmon polaritons has been proven to break the diffraction limit and deliver the high imaging resolution.However,most previously reported studies suffer from the inflexible pattern pitch for a certain structure ascribed to fixed excitation mode.In this work,the large area deep subwavelength interference lithography with tunable pattern period based on BPPs is proposed.By simply tuning the incident angle,the spatial frequencies of the selected BPPs modes squeezed through hyperbolic metamaterial changes correspondingly.As a result,the pitch of the interference pattern is continuously altered.The results demonstrate that one-dimensional and two-dimensional periodic patterns with pitch resolution ranging from 45 nm?^?/10?to 115 nm?^?/4?can be generated under 436 nm illumination.Additionally,the general method of designing such an interference lithography system is also discussed,which can be used for nanoscale fabrication in this fashion.3.Deep subwavelength SPs interference lithography.In this paper,a discrete SPs interference lithography technique based on Al-PR-Al structure is proposed,and the lithography pattern with 32nm half-period resolution is realized in experiments.This separated lithography method not only reducing the difficulty of lithography process,but also elongate the working life of mask.As a results,the cost of lithography would be controlled effectively.