Extreme ultraviolet photomask and methods and apparatuses for manufacturing the extreme ultraviolet photomask

1. A method of manufacturing a photomask, comprising:

forming a multilayer on a photomask substrate, such that the multilayer can be used as a Bragg reflector with respect to an extreme ultraviolet light;

forming an upper layer on the photomask substrate, such that the multilayer is between the photomask substrate and the upper layer ; and

patterning the upper layer to form an upper pattern having an inclined sidewall, wherein patterning the upper layer includes anisotropically etching the upper layer using charged particles moving in parallel to a first direction inclined toward a top surface of the upper layer.

2. The method as claimed in claim 1 , wherein anisotropically etching the upper layer includes maintaining the photomask substrate fixed during the etching.

3. The method as claimed in claim 2 , wherein anisotropically etching the upper layer includes forming the upper pattern to have a cross section of a parallelogram.

4. The method as claimed in claim 1 , wherein anisotropically etching the upper layer includes rotating the photomask substrate around a rotating axis parallel to a normal to a top surface of the photomask during the etching.

5. The method as claimed in claim 4 , wherein rotating the photomask substrate includes setting the photomask substrate at discrete angles around the rotating axis during the etching.

6. The method as claimed in claim 4 , wherein rotating the photomask substrate includes continuously rotating the photomask substrate around the rotating axis during the etching.

7. The method as claimed in claim 4 , wherein anisotropically etching the upper layer includes forming the upper pattern to have a cross section of an inverted trapezoid.

8. The method as claimed in claim 1 , wherein the upper layer is formed of a material configured to absorb an extreme ultraviolet light.

9. The method as claimed in claim 1 , further comprising forming a buffer layer between the upper layer and the multilayer, the buffer layer including at least one material having an etching selectivity with respect to the upper layer.

10. The method as claimed in claim 1 , further comprising, after forming the upper pattern:

forming an absorbing pattern on the photomask substrate using the upper pattern as a molder; and

removing the upper pattern to expose a sidewall of the absorbing pattern.

11. The method as claimed in claim 10 , wherein forming the absorbing pattern includes:

forming an absorbing layer on the photomask substrate to surround the upper pattern, such that a space around the upper pattern is filled; and

etching back the absorbing layer to expose a top surface of the upper pattern.

12. The method as claimed in claim 1 , wherein anisotropically etching the upper layer includes arranging the photomask substrate with the upper layer thereon in a plasma etching chamber, such that the plasma etching chamber generates the charged particles to be directed at an oblique angle with respect to a top surface of the upper layer.

13. The method as claimed in claim 12 , wherein anisotropically etching the upper layer further comprises:

controlling a moving direction of the charged particles in the plasma etching chamber via a Faraday cage; and

controlling an angle between the photomask substrate and the first direction via a position controller.

14. The method as claimed in claim 13 , wherein anisotropically etching the upper layer further comprises controlling a rotation of the photomask on a rotating axis thereof via a rotation controller in the position controller.

15. The method as claimed in claim 1 , wherein patterning the upper layer to form the upper pattern includes forming a plurality of separate upper patterns spaced apart from each other on the multilayer, such that a top surface of the multilayer facing the upper patterns is substantially flat and defines an acute angle with one sidewall of each of the upper patterns.

16. The method as claimed in claim 15 , wherein patterning the upper layer to form the upper pattern includes exposing only substantially flat surfaces of the multilayer, such that extreme ultraviolet light incident directly on the multilayer is reflected from the multilayer.

17. The method as claimed in claim 1 , wherein the multilayer and the upper layer are formed of different materials, such that extreme ultraviolet light is reflected from the multilayer and absorbed into the upper layer.