METHOD FOR REPAIRING OPTICAL ELEMENTS, AND OPTICAL ELEMENT

1 - 11 . (canceled)

12 . A method of modifying an EUV projection exposure collector which comprises a first coating and a second coating, the first coating being between the second coating and a surface of the collector, the method comprising:

a) using a first chemical solution to at least partially remove the first coating; and

b) applying a third coating to at least partially replace the removed first coating,

wherein:

the first coating comprising a first material comprising at least one material selected from the group consisting of nitride Si x N y , zirconium nitride Zr x N y , titanium oxide Ti x O, and yttrium oxide Y x O y ;

the second coating comprising a second material,

the first chemical solution has a first etching rate for the first material;

the first chemical solution has a second etching rate for the second material; and

the first etching rate is at least five times greater than the second etching rate.

13 . The method of claim 12 , wherein a) comprises completely removing the first coating.

14 . The method of claim 12 , wherein the first chemical solution comprises an aqueous acid.

15 . The method as claimed in claim 12 , wherein the first chemical solution comprises at least one acid selected from the group consisting of phosphoric acid H 3 PO 4 , hydrofluoric acid HF, nitric acid HNO 3 , perchloric acid HClO 4 , tetrafluoroboric acid HBF 4 , formic acid HCOOH, acetic acid CH 3 COOH, sulfuric acid H 2 SO 4 , and hydrochloric acid HCl.

16 . The method of claim 12 , further comprising, prior to a), applying a second chemical solution which is different from the first chemical solution.

17 . The method of claim 16 , wherein the second chemical solution comprises a different substance composition from the first chemical solution.

18 . The method of claim 16 , wherein the second chemical solution comprises a concentration of components which is different from the first chemical solution.

19 . The method of claim 16 , wherein the second chemical solution comprises an aqueous acid.

20 . The method of claim 16 , wherein the second chemical solution comprises at least one acid selected from the group consisting of phosphoric acid H 3 PO 4 , hydrofluoric acid HF, nitric acid HNO 3 , perchloric acid HClO 4 , tetrafluoroboric acid HBF 4 , formic acid HCOOH, acetic acid CH 3 COOH, sulfuric acid H 2 SO 4 , and hydrochloric acid HCl.

21 . The method of claim 12 , wherein, prior to b), the collector is treated with a solvent.

22 . The method of claim 12 , wherein the second coating comprises a plurality of alternately layers of molybdenum and silicon.

23 . The method of claim 12 , wherein the second coating comprises a layer comprising ruthenium, palladium, platinum or gold.

24 . The method of claim 12 , wherein the third coating comprises titanium nitride, titanium oxide, silicon nitride or silicon oxide.

25 . A collector comprising a first coating and a second coating, wherein:

the first coating is between the second coating and a surface of the collector;

the first coating comprises at least one material comprising at least one material selected from the group consisting of nitride Si x N y , zirconium nitride Zr x N y , titanium oxide Ti x O, and yttrium oxide Y x O y ;

the second coating comprises: a) a plurality of alternately layers of molybdenum and silicon; or b) a layer comprising ruthenium, palladium, platinum or gold; and

the collector is an EUV projection exposure collector.

26 . The collector of claim 25 , wherein the second coating comprises a plurality of alternately layers of molybdenum and silicon.

27 . The collector of claim 25 , wherein the second coating comprises a layer comprising ruthenium, palladium, platinum or gold.

28 . The collector of claim 25 , further comprising a third coating between the first and second coatings, wherein the third coating comprises titanium nitride, titanium oxide, silicon nitride or silicon oxide.

29 . The collector of claim 25 , wherein the collector is a grazing incidence collector.

30 . An apparatus, comprising:

a collector according to claim 25 ;

an illumination system configured to illuminate a reticle; and

a projection optical unit configured to project an image of the reticle onto a wafer.

31 . A method, comprising:

providing an apparatus which comprises a collector according to claim 25 , an illumination system and a projection optical unit;

using the illumination system to illuminate a reticle; and

using the projection optical unit to project at least a portion of the illuminated reticle onto a wafer.