The Key Techniques Research On Super-resolution Of Plasmonic Lithography Device

Since the first integrated circuit was conceptualized and built,there has been a continuous development in the lithography technology.The conventional projection type photolithography approach to nanoscale manufacturing is facing possibly insurmountable challenges,especially to invent novel technical solutions that remain economical for the next generation of semi-conductor integrated circuits.Although extreme ultra violet(EUV)lithography with the next generation photo-masks and 193 nm immersion lithography with double patterning are expected to deliver 22 nm and smaller nodes,it still cannot effectively address the reliability and cost issues required for mass production.However,the resolution of proximity surface placmonic(SP)lens lithography is still facing technical hurdle,which is called the near-field diffraction limit associated with illumination light wavelength and working distance between the imaging devices and objects.Higher resolution SP lithography inevitably brings shorter working distance,so mask or optical direct-writing head are usually physically contacted with the photo-resist(Pr)recording structure for deep subwavelength resolution lithography experiment.The dissertation focuses on the research of amplifying evanescent waves to go far beyond the near-field diffraction limit and achieves the resolution enhancement of proximity SP lens lithography.Based on the principle,the key technology of SP lithography prototype is studied.The alignment method for PL is essential to circuit manufacturing and other multilayer applications.We obtained an alignment signal with sensitivity better than 20 nm by using the Moiré fringe image that is generated by overlaying two gratings with close periods.According to the diffraction theory,Moiré fringe is independent of the illumination light wavelength and the length of the gap between the mask and the substrate,which make it very suitable for the prototype of PL.However,the alignment of Moiré fringes cannot fully guarantee the alignment of the mask and the substrate because the Moiré fringe repeats itself when the mask and substrate are offset by a fixed displacement.To eliminate the ambiguity,boxes and crosses alignment marks are designed beside the grating marks on the substrate and the mask,respectively.A two-step alignment scheme including coarse alignment and fine alignment is explored in the auto alignment system.The experimental results of overlay indicate that PL can obtain sub-100 nm alignment accuracy over an area of 1 cm2 by using the proposed two-step alignment scheme.Furthermore,the auto alignment system and its process are also fully scalable for 4 in.or larger substrate processing.Via the substrate-mask mismatch compensation,better stages and precise environment control,it is expected that much higher overlay accuracy is feasible in the prototype of PL.In this paper,we present a low-cost and high-resolution lithography prototype by utilizing surface plasmons.In the PL prototype,a metal-photoresist-metal plasmonic cavity lens is adopted to amplify evanescent waves,which can solve the problems in conventional near-field optical lithography such as poor fidelity,low contrast and short working distance.We achieved the photoresist patterns with high resolution,high contrast and high exposure depth experimentally by using an Hg lamp with 365 nm wavelength.Holes array patterns with radius of 50 nm and period of 160 nm were realized.Moreover,the grating array patterns with line width of 60 nm and period of 120 nm were successfully achieved.Furthermore,we introduced a step exposure method to fabricate a 5×5 array of grating patterns with a step length of 300 ?m and the uniform patterns cover the whole area of about 2×2 mm2.Step exposure is valuable,which makes SPL have the ability to obtain a large-area pattern exposure,especially in the condition that the mask area is far smaller than the exposure region.It is believed that this prototype provides a low-cost,high-throughput and high-resolution nano-fabrication route for fabricating nanostructure devices.The goal of this research project is to design,manufacture,assemble and calibrate a state-of-the-art plasmonic nanolithography machine.This project is a result of cooperation with the colleagues of state key laboratory of optical technologies on nano-fabrication and micro-engineering,institute of optics and electronic.PL has many advantages,such as high resolution,lower cost,and high speed.What's more,the PL is highly flexible,user friendly,and has the potential to achieve a large-area pattern exposure and multilayer nanostructure fabrication.