Reflective optical element and euv lithography appliance

Abstract

A reflective optical element and an EUV lithography appliance containing one such element are provided, the appliance displaying a low propensity to contamination. The reflective optical element has a protective layer system includes at least two layers. The optical characteristics of the protective layer system are between those of a spacer and an absorber, or correspond to those of a spacer. The selection of a material with the smallest possible imaginary part and a real part which is as close to 1 as possible in terms of the refractive index leads to a plateau-type reflectivity course according to the thickness of the protective layer system between two thicknesses d 1 and d 2 . The thickness of the protective layer system is selected in such a way that it is less than d 2 .

1 - 26 . (canceled) 
     
     
         27 . A reflective optical element for the extreme ultraviolet (EUV) and soft X-ray wavelength regions, the reflective optical element comprising:
 a multilayer system; and   a protective layer system, wherein:   the protective layer system comprises at least three layers, and a first layer at a vacuum side and a second layer of the at least three layers of the protective layer system each comprise an oxide.   
     
     
         28 . The reflective optical element of  claim 27 , wherein the first layer of the protective layer system is selected from the group consisting of SiO 2 , Y 2 O 3  and ZrO 2 . 
     
     
         29 . The reflective optical element of  claim 27 , wherein the second layer of the protective layer system comprises one or more materials selected from the group consisting of silicon dioxide in various stoichiometric relations, and ZrO. 
     
     
         30 . The reflective optical element according to  claim 27 , wherein the first layer of the protective layer system comprises SiO 2 , while the second layer of the protective layer system comprises silicon dioxide in various stoichiometric relations. 
     
     
         31 . The reflective optical element according to  claim 30 , wherein the first layer of the protective layer system comprises SiO 2 , while the second layer of the protective layer system comprises SiO. 
     
     
         32 . The reflective optical element according to  claim 28 , wherein the first layer of the protective layer system comprises Y 2 O 3 , while a third layer of the protective layer system comprises Y. 
     
     
         33 . The reflective optical element according to  claim 28 , wherein the first layer of the protective layer system comprises ZrO 2 , while the second layer of the protective layer system comprises ZrO. 
     
     
         34 . The reflective optical element according to  claim 27 , wherein a third layer of the protective layer system comprises Y. 
     
     
         35 . The reflective optical element according to  claim 27 , wherein the multilayer system comprises alternating layers formed on a substrate, the alternating layers comprising Mo and Si, respectively. 
     
     
         36 . An extreme-ultraviolet (EUV) lithography appliance comprising at least one reflective optical element according to  claim 27 . 
     
     
         37 . A reflective optical element for the extreme ultraviolet (EUV) and soft X-ray wavelength regions, the reflective optical element comprising:
 a multilayer system; and   a protective layer system, wherein:   the protective layer system comprises at least two layers, and a first layer at a vacuum side of the at least two layers of the protective layer system comprises one or more materials selected from the group consisting of Nb, BN, B 4 C, Y, amorphous C, Si 3 N 4 , and SiC.   
     
     
         38 . The reflective optical element according to  claim 37 , wherein a second layer of the at least two layers of the protective layer system comprises one or more materials selected from the group consisting of Y 2 O 3 , ZrO 2 , and SiO 2  in various stoichiometric relations. 
     
     
         39 . The reflective optical element according to  claim 38 , wherein the protective layer system comprise a third layer. 
     
     
         40 . The reflective optical element according to  claim 39 , wherein the third layer comprises Y. 
     
     
         41 . The reflective optical element according to  claim 37 , wherein the protective layer system comprise at least three layers. 
     
     
         42 . The reflective optical element according to  claim 37 , wherein the multilayer system comprises alternating layers formed on a substrate, the alternating layers comprising Mo and Si, respectively. 
     
     
         43 . An extreme-ultraviolet (EUV) lithography appliance comprising at least one reflective optical element according to  claim 37 .