Method of manufacturing EUV photo masks

1. A method of manufacturing a photo mask, the method comprising:

forming an etching mask layer having patterns over a target layer of the photo mask to be etched;

covering an edge portion of the photo mask with an etching hard cover, while a region of the target layer to be etched is exposed through an opening of the etching hard cover, the edge portion including a part of an upper surface and a part of a side surface of the photo mask; and

etching the target layer by plasma etching through the opening.

2. The method of claim 1 , during the etching comprises preventing active species of plasma from attacking a backside of the photo mask.

3. The method of claim 1 , wherein the cover layer is separated from the etching mask layer.

4. The method of claim 1 , wherein the cover layer is in contact with the etching mask layer.

5. The method of claim 1 , wherein the cover layer is in contact with the target layer to be etched.

6. The method of claim 1 , wherein:

the etching mask layer is a resist pattern, and

the target layer is a hard mask layer on an absorber layer of the photo mask.

7. The method of claim 1 , wherein:

the etching mask pattern is a hard mask pattern, and

the target layer is an absorber layer of the photo mask.

8. The method of claim 1 , wherein:

the etching mask layer is a resist pattern, and

the target layer includes an absorber layer, a capping layer and a reflective multilayer disposed over a substrate of the photo mask.

9. A method of manufacturing a photo mask, comprising:

forming a circuit pattern in an absorber layer of a mask blank, the mask blank including a substrate, a reflective multilayer on the substrate, a capping layer on the reflective multiplayer and an absorber layer;

forming an etching mask layer having a black border pattern over the absorber layer;

covering an edge portion of the absorber layer with an etching hard cover, while a region corresponding the black border pattern is exposed through an opening of the etching hard cover; and

etching the absorber layer, the capping layer and the reflective multilayer by plasma etching through the opening, while preventing active species of plasma from attacking a backside of the mask blank.

10. The method of claim 9 , wherein the cover layer is separated from the etching mask layer.

11. The method of claim 9 , wherein the cover layer is in contact with the etching mask layer.

12. The method of claim 9 , wherein the etching hard cover is made of ceramic.

13. The method of claim 12 , wherein the etching hard cover has a frame shape having the opening and a frame portion defining the opening and a side frame from which the frame portion extends.

14. An etching apparatus for patterning a reflective phot mask, comprising:

a mask stage;

a etching hard cover; and

an electric chuck to hold the reflective photo mask, wherein:

the electric chuck including a cathode and the mask stage includes a capture ring surrounding the electric chuck, and

a cathode protrusion is provided on the cathode.

15. The etching apparatus of claim 14 , wherein the etching hard cover is configured to move up and down relative to the mask stage.

16. The etching apparatus of claim 14 , wherein the etching hard cover is supported by one or more support posts.

17. The etching apparatus of claim 14 , wherein a stage protrusion is provided at a flat surface of the capture ring of the mask stage.

18. The etching apparatus of claim 14 , wherein the stage protrusion is an O-ring disposed in a groove formed in the capture ring.

19. The etching apparatus of claim 14 , wherein the stage protrusion is a protruding part of the capturing ring.

20. The etching apparatus of claim 14 , wherein the electric chuck is configured to move up and down relative to the capture ring.