Methods for forming optical films

1. A method, comprising:

providing a layer comprising a plurality of spaced-apart lines of a first material extending along a first direction;

forming a line of a second material on opposing surfaces of each line of the first material, the first and second materials being different and adjacent lines of the second material being discontinuous;

after forming the lines of the second material, forming pairs of spaced-apart lines of a third material between and separated from adjacent pairs of the lines of the second material, adjacent lines of the third material being discontinuous and having a thickness that is different from a thickness of the lines of the first material, and

forming a cap layer, the cap layer encapsulating the lines of the first, second and third materials wherein, after forming the cap layer, the lines of the third material have a thickness that is at most 95% of the thickness of the lines of the first material.

2. The method of claim 1 , wherein the lines of the first material have a pitch of 200 nm or less, and the first and third materials are different.

3. The method of claim 2 , wherein forming the lines of the second material comprises:

forming a continuous layer of the second material on the layer comprising the lines of the first material; and

removing portions of the continuous layer of the second material to provide the lines of the second material.

4. The method of claim 3 , wherein the continuous layer of the second material is formed using atomic layer deposition.

5. The method of claim 3 , wherein the continuous layer of the second material conforms to a surface profile of the layer comprising the plurality of lines of the first material.

6. The method of claim 3 , wherein removing the portions of the continuous layer of the second material comprises etching the layer of the second material.

7. The method of claim 1 , wherein the second material has a refractive index of 1.8 or more and an extinction coefficient of 1.8 or more for a wavelength λ, that is 400 nm or less.

8. The method of claim 1 , wherein the lines of the second material have a line width of 20 nm or less.

9. The method of claim 1 , wherein the lines of the second material have a thickness of 100 nm or more.

10. The method of claim 1 , wherein the lines of the second material have an aspect ratio of 5:1 or more.

11. The method of claim 1 , wherein forming the lines of the third material comprises:

forming a continuous layer of a fourth material over the lines of the second material; and

forming a layer of the third material over the layer of the fourth material,

wherein the second and third materials are different from the fourth material.

12. The method of claim 11 , wherein forming the lines of the third material further comprises removing portions of the continuous layer of the third material to provide the lines of the third material.

13. The method of claim 11 , wherein the third material is the same as the second material.

14. The method of claim 13 , wherein the second material has a refractive index of 1.8 or more and an extinction coefficient of 1.8 or more for a wavelength λ that is 400 nm or less.

15. The method of claim 1 , wherein the lines of the third material have a line width of 20 nm or less.

16. The method of claim 1 , wherein the lines of the third material have a thickness that is different from a thickness of the lines of the second material.

17. The method of claim 16 , wherein the thickness of the lines of the second material is greater than the thickness of the lines of the third material.