DUV LaF3 thin film deposited by IBS, thermal boat and electron beam evaporation

SHI Guang; MEI Lin; GAO Jin-song; ZHANG Li-chao; ZHANG Ling-hua

doi:10.7510/jgjs.issn.1001-3806.2013.05.007

In order to satisfy the requirements of coatings of deep ultraviolet(DUV) lithography objective lens and obtain coatings with low optical losses, high stability and long lifetimes, a deposition method should be confirmed first. LaF3 single layers were deposited upon fused silica by ion beam sputtering(IBS), boat and electron beam evaporation with optimized process parameters respectively. Firstly, based on spectrophotometry, the refractive index n and extinction coefficients k in 185nm~800nm of the LaF3 layer deposited with three methods were obtained. Secondly, the surface roughness of LaF3 layers was measured by means of atomic-force microscope(AFM). Finally, X-ray diffraction(XRD) was used to investigate the microstructure of LaF3 layer. Experimental results indicate that, LaF3 layer deposited by IBS has the highest refractive index and the lowest surface roughness but the highest extinction coefficients; for LaF3 layer deposited by electron beam, although its extinction coefficients is low, but the refractive index and surface roughness doesn't seem good; as for thermal boat, all parameters discussed here is intermediate between that of LaF3 layer deposited by IBS and electron beam. Finally,based on consideration with every factors, thermal boat evaporation method is most suitable for depositing DUV LaF3 film.

DUV LaF3 thin film deposited by IBS, thermal boat and electron beam evaporation

1. Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China

Received Date: 2013-02-25

Accepted Date: 2013-03-18

Available Online: 2013-09-25

Abstract: In order to satisfy the requirements of coatings of deep ultraviolet(DUV) lithography objective lens and obtain coatings with low optical losses, high stability and long lifetimes, a deposition method should be confirmed first. LaF3 single layers were deposited upon fused silica by ion beam sputtering(IBS), boat and electron beam evaporation with optimized process parameters respectively. Firstly, based on spectrophotometry, the refractive index n and extinction coefficients k in 185nm~800nm of the LaF3 layer deposited with three methods were obtained. Secondly, the surface roughness of LaF3 layers was measured by means of atomic-force microscope(AFM). Finally, X-ray diffraction(XRD) was used to investigate the microstructure of LaF3 layer. Experimental results indicate that, LaF3 layer deposited by IBS has the highest refractive index and the lowest surface roughness but the highest extinction coefficients; for LaF3 layer deposited by electron beam, although its extinction coefficients is low, but the refractive index and surface roughness doesn't seem good; as for thermal boat, all parameters discussed here is intermediate between that of LaF3 layer deposited by IBS and electron beam. Finally,based on consideration with every factors, thermal boat evaporation method is most suitable for depositing DUV LaF3 film.

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Reference (14)

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DUV LaF3 thin film deposited by IBS, thermal boat and electron beam evaporation

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