Lithographic apparatus and method

1. A lithographic apparatus comprising:

a support structure comprising first and second portions, wherein:

the first portion is different from the second portion;

the first portion is configured to support a patterning device,

the second portion comprises a grating,

the grating comprises first and second reflective portions,

the first and second reflective portions are positioned in an alternating pattern,

the second reflective portions have a first reflectivity smaller than a second reflectivity of at least sub-portions of the first reflective portions, the first reflectivity being greater than zero, and

the patterning device is configured to impart an EUV radiation beam with a pattern in its cross-section to form a patterned EUV radiation beam; and

a projection system configured to project the patterned EUV radiation beam onto a target portion of a substrate.

2. The lithographic apparatus of claim 1 , wherein the first and second reflective portions comprise unpatterned areas.

3. The lithographic apparatus of claim 2 , wherein the first and second reflective portions comprise rectangular shapes.

4. The lithographic apparatus of claim 1 , wherein:

each of the first reflective portions comprises a sub-grating having reflective lines and absorbing lines; and

each of the second reflective portions comprises an unpatterned area.

5. The lithographic apparatus of claim 4 , wherein the grating is configured such that the first reflectivity substantially matches a mean reflectivity of the reflective lines and the absorbing lines.

6. The lithographic apparatus of claim 1 , wherein the grating further comprises an absorbing portion located between a pair of first and second reflective portions from among the first and second reflective portions.

7. The lithographic apparatus of claim 1 , wherein the grating is configured such that a mean intensity of radiation reflected by the first reflective portions and received by the substrate is substantially equal to a mean intensity of radiation reflected by the second reflective portions and received by the substrate.

8. The lithographic apparatus of claim 1 , wherein:

each of the second reflective portions comprises a layer of absorbing material located over a mirror;

the layer of absorbing material is configured to allow transmission of at least a portion of the EUV radiation beam towards the mirror; and

the mirror is configured to reflect at least a sub-portion of the at least a portion of the EUV radiation beam towards the layer of absorbing material.

9. The lithographic apparatus of claim 1 , wherein the first reflectivity is half of the second reflectivity.

10. The lithographic apparatus of claim 1 , wherein the support structure further comprises a second grating having an opposite orientation to the grating.

11. The lithographic apparatus of claim 1 , wherein the support structure further comprises another grating extending in a transverse direction to the grating.

12. The lithographic apparatus of claim 1 , wherein the grating is configured such that a first radiation dose per unit area projected onto the substrate from the second reflective portions is substantially equal to a second radiation dose per unit area projected onto the substrate from the first reflective portions.

13. The lithographic apparatus of claim 1 , further comprising an alignment apparatus configured to:

measure a center of gravity of an image of the grating projected onto the substrate; and

measure a dose of the EUV radiation beam received by the substrate based on the center of gravity.

14. The lithographic apparatus of claim 1 , further comprising an alignment apparatus configured to:

measure a position of an image of the grating projected onto the substrate; and

determine a location of a focal plane of the projection system based on the position of the image of the grating.

15. The lithographic apparatus of claim 1 , wherein the support structure further comprises another grating having a pattern that is a mirror image of a pattern of the grating.

16. A patterning device comprising:

first and second reflective portions, wherein:

the second reflective portions have a first reflectivity smaller than a second reflectivity of at least sub-portions of the first reflective portions;

each of the first reflective portions comprises a sub-grating having reflective lines and absorbing lines;

the first reflectivity is greater than zero and substantially matches a mean reflectivity of the reflective lines and the absorbing lines; and

each of the second reflective portions comprises an unpatterned area.

17. The patterning device of claim 16 , wherein the patterning device further comprises an absorbing portion located between a pair of first and second reflective portions from among the first and second reflective portions.

18. A support structure of a lithography apparatus comprising:

first and second portions, wherein:

the first portion is different from the second portion;

the first portion is configured to support a patterning device;

the second portion comprises a grating;

the grating comprising first and second reflective portions;

the first and second reflective portions are positioned in an alternating pattern;

the second reflective portions have a first reflectivity smaller than a second reflectivity of at least sub-portions of the first reflective portions; and

the first reflectivity is greater than zero.

19. The support structure of claim 18 , wherein the grating further comprises an absorbing portion located between a pair of first and second reflective portions from among the first and second reflective portions.