Method of manufacturing EUV photo masks

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

forming an etching mask layer having circuit patterns over a target layer of the photo mask to be etched, the photo mask including a backside conductive layer;

covering an edge portion of the target layer 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; and

etching the target layer by plasma etching through the opening, while preventing active species of plasma from attacking the backside conductive layer.

2. The method of claim 1 , wherein the etching hard cover is reusable.

3. The method of claim 1 , wherein the etching hard cover is made of ceramic.

4. The method of claim 1 , 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.

5. The method of claim 4 , wherein the frame portion covers the edge portion.

6. The method of claim 4 , wherein a bottom surface of the frame portion is in contact with the etching mask layer.

7. The method of claim 4 , wherein a bottom surface of the frame portion is not in contact with the etching mask layer with a gap.

8. The method of claim 7 , wherein the gap is equal to or less than 1 mm.

9. The method of claim 4 , wherein a bottom surface of the frame portion includes a protrusion.

10. The method of claim 9 , wherein the protrusion is a line shape.

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

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

forming an etching mask layer having circuit patterns over a target layer of the photo mask to be etched, the photo mask including a backside conductive layer;

placing the photo mask on a stage in an etching apparatus; and

etching the target layer by plasma etching in the etching apparatus, wherein:

the stage comprises a capture ring and an electric chuck mechanism including a cathode, and

the photo mask is placed on the stage such that a bottom surface of the photo mask where no backside conductive layer is disposed is placed above the capture ring, and the backside conductive layer is placed on the cathode.

13. The method of claim 12 , wherein the bottom surface of the photo mask where no backside conductive layer is disposed is in contact with the capture ring.

14. The method of claim 13 , wherein the capture ring includes a protrusion in contact with the bottom surface of the photo mask where no backside conductive layer is disposed.

15. The method of claim 13 , wherein the capture ring includes a groove in which an O-ring in contact with the bottom surface of the photo mask where no backside conductive layer is disposed is disposed.

16. The method of claim 12 , wherein the bottom surface of the photo mask where no backside conductive layer is disposed is not in contact with the capture ring.

17. The method of claim 12 , wherein the backside conductive layer is not in contact with the capture ring.

18. The method of claim 17 , wherein a gap between the bottom surface of the photo mask where no backside conductive layer is disposed and the capture ring is equal to or less than 0.2 mm.

19. An etching apparatus for etching a target layer of a photo mask, comprising:

a mask stage; and

an electric chuck to hold the photo mask, wherein:

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

a first protrusion is provided at a flat surface of the capture ring of the mask stage,

a second protrusion is provided on the cathode, and

the electric chuck is configured to move up and down relative to the capture ring.

20. The etching apparatus of claim 19 , wherein the first protrusion is an O-ring disposed in a groove formed in the capture ring.