Study On Ni/Ti Mirrors And Mo/Si Multilayer Protective Layer Prepared By Reactive Sputtering

The surface and interface properties of multilayers are one of the most important factors affecting the reflectivity of multilayers.Interfacial barrier layers,co-sputtering,and reactive magnetron sputtering are very important technical means to improve interfacial properties.Firstly,the theoretical design and simulation of Ni/Ti neutron multilayer mirrors are carried out.Ni/Ti multilayers are prepared by nitrogen-oxygen reactive magnetron sputtering technology,and the effect of the preparation process on Ni/Ti multilayer films is studied.Secondly,the oxide protective layer of the Mo/Si multilayer for the extreme ultraviolet lithography machine is designed and simulated,and the oxide protective layer is prepared by oxygen reactive magnetron sputtering technology.The preparation process of the oxide protective layer and its effect on the Mo/Si multilayer are studied.The main results of this thesis are as follows:1)The design and calculation results of the Ni/Ti neutron multilayer mirror show that with the increase of the film thickness ratioγ,the incident angle decreases,and the bandwidth widens at first and then narrows.Whenγ=0.5,the reflection peak bandwidth is the largest.The neutron reflectivity is affected by the interface width,and the larger the interface width is,the lower the reflectivity is.Take the periodic thickness D=5nm and periods N=180 as an example:when the interface width is 0.5nm,the neutron reflectivity is 98.09%;when the interface width increases to 1 nm,the neutron reflectivity is reduced to 81.05%.The interface width is mainly related to the preparation process,and an excellent preparation process can keep the interface width at a relatively small value.The optimisation results of Ni/Ti multilayers prepared by nitrogen-oxygen reactive sputtering show that the mass flowmeter can control the Ar flow rate and change the N₂ and O₂ flow rates（N₂:O₂=4:1）so as to adjust the nitrogen-oxygen doping ratio.In this thesis,the optimised nitrogen-oxygen doping ratio is 22.5%;when the number of cycles is 50,compared with the Ni/Ti multilayers sputtered in pure Ar atmosphere,the interface width of Ni-on-Ti and Ti-on-Ni is reduced from 1.923 nm and 2.986 nm to 1.295 nm and 1.255 nm,and the interface width decreases obviously.Appropriate nitrogen-oxygen doping ratios can inhibit the growth of the interface width of Ni/Ti multilayers and improve the interface quality.The stress study of Ni/Ti multilayer films shows that there is a critical nitrogen oxygen doping ratio that can cause the stress of Ni/Ti multilayer films to transition from compressive stress to tensile stress.The design and calculation results of the oxide protective layer for the Mo/Si multilayer mirror show that the peak reflectivity of the Mo/Si multilayer decreases with the increase in protective layer thickness.The peak reflectivity of the Mo/Si multilayer without a protective layer is 73.33%,while the reflectivity attenuation of the protective layer added at 2-3 nm is only about 2%,and that of the 5 nm protective layer is about8%.Taking the 3 nm protective layer as an example,adding Nb₂O₅ protective layer resulted in the highest reflectivity of 72.28%,followed by Zr O₂ of 72.42%,and Ti O₂with the lowest reflectivity of 71.45%.The optimisation results of the process of preparing an oxide protective layer by oxygen reactive sputtering show that with an increase in the oxygen doping ratio,the film tends to have an amorphous phase,and when the oxygen doping ratio is 20%,the glass substrate tends to be colourless and transparent.Ti,Zr,and Nb all observed similar phenomena,indicating the formation of corresponding oxides.The XPS results showed that Ti,Nb,and Zr were completely oxidized to form Ti O₂,Nb₂O₅,and Zr O₂;The extreme ultraviolet reflectivity test results of the BL08B line station of the National Synchrotron Radiation Laboratory are consistent with the theoretical design,and the reflectivity decreases with the increase in thickness of the protective layer.The peak reflectivity of the actual prepared Mo/Si multilayer without a protective layer is 66.78%,while the reflectivity attenuation of the protective layer added at 2-3 nm is only about 4%,and that of the 5nm protective layer is about 9%.Taking the 3 nm protective layer as an example,the highest reflectivity of the Ti O₂ protective layer is 62.49%,followed by Nb₂O₅ at 61.38%,and the lowest reflectivity of Zr O₂ is 60.76%.The thickness of the protective layer of 2-3 nm has less attenuation of the reflectivity,so it is more suitable for lithography.In this thesis,the surface and interface properties of multilayers are obviously optimized by reactive magnetron sputtering,which provides a promising preparation method for high-performance nano-multilayer mirrors.There are 51 figures,17 tables and 95 references in this thesis.