Methods of compensating lens heating, lithographic projection system and photo mask

1. A method of compensating lens heating of a projection lens in a lithographic projection apparatus during projection of a mask onto a substrate, the method comprising:

providing a layout pattern including a regular pattern that is arranged substantially symmetrical in a first region;

providing a sub-resolution pattern including a plurality of sub resolution structural elements;

arranging the sub-resolution pattern in a second region, so as to minimize non-homogenous lens heating of a projection apparatus in case of a lithographic projection;

providing a photo mask including the layout pattern and the sub-resolution pattern; and

performing a lithographic projection using the photo mask.

2. The method according to claim 1 , wherein the second region is different to the first region.

3. The method according to claim 1 , wherein the pattern in the first region comprises further structural elements, the second region being arranged within the further structural elements.

4. The method according to claim 1 , wherein the sub-resolution pattern comprises transparent structural elements on the photo mask.

5. The method according to claim 1 , wherein the sub-resolution pattern comprises light absorbing or attenuating structural elements on the photo mask.

6. The method according to claim 1 , wherein the non-homogenous lens heating is calculated during a simulation step.

7. The method according to claim 1 , wherein the non-homogenous lens heating is calculated during a measurement of an aberration parameter.

8. The method according to claim 7 , wherein the aberration parameter is measured in a steady state of the projection apparatus.

9. The method according to claim 8 , wherein the steady state includes a steady state of thermal heating of one or more lens elements.

10. The method according to claim 1 , further comprising:

providing a semiconductor wafer having a resist layer formed over an upper surface thereof, wherein performing a lithographic projection comprises defining a pattern in the resist layer; and

modifying the upper surface of the semiconductor wafer based on the pattern.

11. A method of compensating lens heating of a projection lens in a lithographic projection apparatus during projection of a mask onto a substrate, the method comprising:

providing a layout pattern including a regular pattern being arranged substantially symmetrical in a first region;

providing a sub-resolution pattern including a plurality of sub-resolution structural elements;

optimizing the sub-resolution pattern in a second region by reducing non symmetrical aberrations of a projection apparatus in case of lithographic projection;

providing a photo mask including the layout pattern and the sub-resolution pattern; and performing a lithographic projection using the photo mask.

12. The method according to claim 11 , wherein the optimizing further comprises selecting feature types, pitches and pattern arrangement of the sub-resolution pattern.

13. The method according to claim 11 , wherein the optimizing further comprises selecting feature types, pitches and pattern arrangement of the sub-resolution pattern within several different sub-regions of the second region.

14. The method according to claim 13 , wherein the sub-resolution pattern is arranged with substantially different orientation with respect to the layout pattern.

15. The method according to claim 11 , wherein the optimizing further comprises determining a pupil fill of a lens of the projection apparatus.

16. The method according to claim 15 , wherein the pupil fill is derived by performing a wavefront measurement of the projection apparatus.

17. The method according to claim 15 , wherein the projection apparatus is capable of providing off-axis illumination.

18. The method according to claim 11 , wherein at least part of structural elements of the sub-resolution pattern are arranged as a sub-resolution assist feature to the layout pattern.

19. The method according to claim 11 , wherein the optimizing comprises inserting, removing, relocating or modifying structural elements of the sub-resolution pattern.

20. The method according to claim 11 , further comprising:

providing a semiconductor wafer having a resist layer formed over an upper surface thereof, wherein performing the lithographic projection comprises defining a pattern in the resist layer; and

modifying the upper surface of the semiconductor wafer based on the pattern.

21. A photo mask capable of compensating lens heating of a projection lens in a lithographic projection apparatus during projection onto a substrate, the photo mask comprising:

a layout pattern including a regular pattern being arranged substantially symmetrical in a first region; and

a sub-resolution pattern including a plurality of sub-resolution structural elements, wherein the sub-resolution pattern in a second region, so as to minimize non-homogenous lens heating of a projection apparatus in case of a lithographic projection.

22. The photo mask according to claim 21 , wherein the sub-resolution pattern is arranged with substantially different orientation with respect to the layout pattern.

23. A lithographic projection system comprising:

an imagining system capable of exposing a photo mask including a layout pattern including a regular pattern being arranged substantially symmetrical in a first region and a sub-resolution pattern including a plurality of sub-resolution structural elements;

a projection system capable of projection light from the photo mask onto a substrate;

a movable stage arranged under the projection system, the movable stage configured to hold a substrate; whereby the sub-resolution pattern in a second region, reduces non-homogenous lens heating of a projection system during a lithographic projection.

24. The lithographic projection system according to claim 23 , wherein the sub-resolution pattern is arranged with substantially different orientation with respect to the layout pattern.

25. A method of making a semiconductor device, the method comprising:

providing a semiconductor wafer with a resist layer formed on a surface thereof;

providing a photo mask comprising a photo mask capable of compensating lens heating of a projection lens in a lithographic projection apparatus during projection onto a substrate, the photo mask comprising a layout pattern including a regular pattern being arranged substantially symmetrical in a first region, and a sub-resolution pattern including a plurality of sub-resolution structural elements, wherein the sub-resolution pattern in a second region, so as to minimize non-homogenous lens heating of a projection apparatus in case of a lithographic projection;

illuminating the resist layer through the photo mask;

developing the resist layer thereby exposing a patterned portion of the semiconductor wafer; and

modifying the upper surface of the semiconductor wafer in relation to the patterned portion.