Methods of reducing defects in directed self-assembled structures

1. A method of reducing the number of defects in a directed self-assembled structure formed on a guiding pre-pattern on a substrate, the method comprising:

(a) applying a first layer comprising a first self-assembly material onto the guiding pre-pattern, the first self-assembly material forming domains whose alignment and orientation are directed by the guiding pre-pattern, thereby creating a first self-assembled structure;

(b) optionally annealing the first self-assembled structure;

(c) directly following step (b), or if step (b) is not performed then directly following step (a): washing away the first self-assembled structure, without removing the guiding pre-pattern; and

(d) after said washing, applying a second layer comprising a second self-assembly material over the substrate, wherein the second layer occupies space previously occupied by the first layer, the second self-assembly material forming a second self-assembled structure having fewer defects than the first self-assembled structure.

2. The method of claim 1 , wherein no etch process is performed between (i) the step of applying the first layer and (ii) the step of applying the second layer.

3. The method of claim 1 , comprising:

washing away the second self-assembled structure; and

after said washing away of the second self-assembled structure, applying a third layer comprising a third self-assembly material over the substrate, wherein the third layer occupies space previously occupied by the first layer, the third self-assembly material forming a third self-assembled structure having fewer defects than the second self-assembled structure.

4. The method of claim 1 , comprising:

annealing the first layer, prior to said washing.

5. The method of claim 1 , comprising:

after the step of washing but before the step of applying the second layer, baking the substrate, thereby removing any residual solvent.

6. The method of claim 1 , comprising:

annealing the second layer.

7. The method of claim 1 , wherein the first self-assembly material and the second self-assembly material are the same kind of material.

8. The method of claim 1 , wherein the first material and the second material both include PS-b-PMMA.

9. The method of claim 1 , wherein the thickness of the second layer is at least about 55 nm.

10. The method of claim 1 , wherein the thickness of the second layer is greater than two times that of a characteristic pitch of the second self-assembled structure.

11. The method of claim 1 , wherein the second self-assembled structure has a pitch that is less than 50 nm.

12. The method of claim 1 , wherein the second self-assembled structure has a pitch that is no greater than about 25 nm.

13. The method of claim 1 , wherein the method of claim 1 is part of an in-line process.

14. The method of claim 13 , wherein the in-line process is a 300 mm wafer process.

15. The method of claim 1 , wherein the thickness of the first layer is less than the thickness of the second layer.

16. The method of claim 1 , wherein the pre-pattern is a chemical pre-pattern.

17. The method of claim 1 , comprising etching the second self-assembled structure.

18. The method of claim 1 , comprising:

annealing the first layer, prior to said washing; and

annealing the second layer.

19. The method of claim 18 , wherein the second self-assembled structure has a pitch that is less than 50 nm.

20. The method of claim 19 , comprising etching the second self-assembled structure.

21. The method of claim 1 , wherein the second self-assembled structure has fewer dislocation defects than the first self-assembled structure.

22. The method of claim 1 , wherein the second self-assembled structure has a dislocation defect density less than or equal to about 25 per square centimeter.

23. A method of reducing the number of defects in a directed self-assembled structure formed on a guiding pre-pattern on a substrate, the method comprising:

(a) applying a first layer comprising a first self-assembly material onto the guiding pre-pattern, the first self-assembly material forming domains whose alignment and orientation are directed by the guiding pre-pattern, thereby creating a first self-assembled structure;

(b) optionally annealing the first self-assembled structure;

(c) directly following step (b), or if step (b) is not performed then directly following step (a): washing away the first self-assembled structure, and leaving behind a modified guiding pre-pattern; and

(d) after said washing, applying a second layer comprising a second self-assembly material onto the modified guiding pre-pattern, the second self-assembly material forming domains whose alignment and orientation are directed by the modified guiding pre-pattern, thereby creating a second self-assembled structure having fewer defects than the first self-assembled structure.

24. The method of claim 23 , wherein no etch process is performed between (i) the step of applying the first layer and (ii) the step of applying the second layer.

25. The method of claim 23 , comprising:

annealing the first layer, prior to said washing.

26. The method of claim 23 , comprising:

annealing the second layer.

27. The method of claim 23 , wherein the first material and the second material both include PS-b-PMMA.

28. The method of claim 23 , wherein the method of claim 23 is part of an in-line process.

29. The method of claim 28 , wherein the in-line process is a 300 mm wafer process.

30. The method of claim 23 , wherein the thickness of the first layer is less than the thickness of the second layer.

31. The method of claim 23 , wherein the pre-pattern is a chemical pre-pattern.

32. The method of claim 23 , comprising etching the second self-assembled structure.

33. The method of claim 23 , wherein the second self-assembled structure has fewer dislocation defects than the first self-assembled structure.

34. The method of claim 23 , wherein the second self-assembled structure has a dislocation defect density less than or equal to about 25 per square centimeter.