Patent ID: 7736820

Claim:
An EUV mask for a lithographic apparatus, the mask comprising: a multi-layer stack comprising a plurality of alternating layers with a multi-layer stack top layer; a spectral filter top layer arranged on the multi-layer stack, the spectral filter top layer comprising: a first spectral purity enhancement layer comprising a material m 1 and having a layer thickness d 1 ; an intermediate layer comprising a material m 2 and having a layer thickness d 2 ; a second spectral purity enhancement layer comprising a material m 3 and having a layer thickness d 3 , the second spectral purity enhancement layer being arranged on the multi-layer stack top layer, wherein the first and second spectral purity enhancement layers comprise independently a material selected from the group of Si 3 N 4 , SiO 2 , ZnS, Te, diamond, CsI, Se, SiC, amorphous carbon, MgF 2 , CaF 2 , TiO 2 , Ge, PbF 2 , ZrO 2 , BaTiO 3 , LiF and NaF, the intermediate layer comprises a material different from the materials from the first and second spectral purity enhancement layer; and a patterned absorber layer arranged on the spectral filter top layer wherein the EUV mask comprises a cap layer arranged directly under the absorber layer, wherein m 1 , m 2 , m 3 , d 1 , d 2 and d 3 are selected to enlarge a ratio of an amount of radiation having a wavelength selected from a first wavelength range of 5-20 nm to an amount of radiation having a wavelength selected from a second wavelength range of 100-400 nm of a source emitting radiation in both wavelength ranges.