Study On Surface Plasmons Super-resolution Li Thography Imaging

The traditional optical image is always limited by the diffraction limit,resulting in optical image resolution is only one half of incident wavelengths. Theessence of the diffraction limit is to carry high frequency information of the finestructure of the object with the behavior of the evanescent wave，which is attenuationexponentially with the increase of the propagation distance and is unable to participatein optical image. In recent years, in order to achieve super diffraction optical image,various methods of the breaking through diffraction limit have been proposed. The rapiddevelopment of the sub-wavelength optics which based on surface plasmons providesan important theoretical basis in order to achieve super diffraction lithography imagingexperimentally. According to the special optical properties of the surface plasmonswave, the super-resolution lithography imaging is implemented experimentally in thisdegree dissertation using separate surface plasmons super-resolution lithographydevices, whose period is200nm and line width is100nm. The main content and theresults of the paper are as follows.1. The briefly analysis is given for the reason that it occurs diffraction, andmethods to improve the optical system imaging resolution under the traditional way areintroduced. Based on the surface plasmons super diffraction imaging, we introduce boththe principle and the several excition ways of the surface plasmon, and the reserchsituation that using metal plat superlens structure breaks through the diffraction limit.Finally, the method of laser interference that is often used to mask fabrication isdescribed.2. Because the thin film materials have important effects on super diffractionlithography imaging quality, the preparation of the high quality film material has beenexplored in this paper. First, the working principles about the magnetron supttering and the electron beam evaporation coating are stated, and then we give both the preparationmethods and the optimization process parameters of the mask material consisting of theCr film, the superlens silver layer and the reflective silver film with thickness of40nm,20nm and50nm, respectively. Using equipments including the profilometer, atomicforce microscope (AFM) and scanning electron microscope (SEM) are used to detectboth the thickness and the morphology of the membrance layer, respectively.3. Based on the separate surface plasmons super-resolution lithography device,laser interference photolithography method is used to fabricate the Cr grating maskgraphics with100nm line width. The grating mask is filled with the PMMA dielectricmaterial. Through multiple spin coating and reactive ion etching (RIE), we get thePMMA dielectric layer with35nm thickness. Under I line mercury lamp light sourcewith365nm wavelength, the optical imaging with sub-wavelength feature size isrealized when the grating mask was used to SP lithography.