Alternating hardmasks for tight-pitch line formation

1. A method for forming fins, comprising:

forming a three-color hardmask fin pattern on a fin base layer, the three-color hardmask fin pattern comprising hardmask fins of three mutually selectively etchable compositions;

masking a region on the three-color hardmask fin pattern, leaving one or more fins of a first color exposed;

etching away all exposed fins of the first color with a selective etch that does not remove fins of a second color or a third color;

etching away the mask and all fins of a second color;

etching fins into the fin base layer by anisotropically etching around remaining fins of the first color and fins of the third color.

2. The method of claim 1 , wherein forming the three-color hardmask fin pattern comprises:

forming fins of the first color on the fin base layer;

depositing a second-color material around the fins of the first color;

etching away fins of the first color, leaving gaps; and

forming fins of a third color in the gaps.

3. The method of claim 2 , wherein forming fins of the first color comprises:

forming self-assembled fins on a seed layer, the self-assembled fins comprising fins of alternating polymer materials;

etching away every other self-assembled fin; and

etching down into a layer of first-color material around the remaining self-assembled fins to form fins of a first color, leaving remaining fins having differing heights.

4. The method of claim 3 , wherein the fins of the first color each comprise a cap of one or more dielectric layers, with different dielectric layers corresponding to different heights of the fins of the first color.

5. The method of claim 3 , wherein forming self-assembled fins comprises applying a block copolymer material having two molecular chains of similar or equal length, wherein one of the two molecular chains is attracted to the seed layer.

6. The method of claim 5 , wherein a first chain of the material comprises polystyrene and wherein a second chain of the material comprises poly(methyl methacrylate).

7. The method of claim 3 , further comprising etching the second-color material to a height lower than a height of the tallest remaining self-assembled fins and greater than a height of the shortest remaining self-assembled fins.

8. The method of claim 3 , wherein etching away fins of the first color comprises etching away the fins of the first color having a greater-than-average height.

9. The method of claim 1 , wherein masking the region comprises forming a mask with a lithographic process having a minimum pitch size that is greater than a fin pitch of the three-color hardmask fin pattern.

10. The method of claim 1 , further comprising:

masking a region on the three-color hardmask fin pattern, leaving one or more fins of the third color exposed; and

etching away all exposed fins of the third color with a selective etch that does not remove fins of the first color or the second color.

11. A method of forming a three-color hardmask fin pattern, comprising:

forming fins of a first color on a fin base layer;

depositing a second-color material around the fins of the first color;

etching away fins of the first color, leaving gaps, wherein the etch further leaves at least one fin of the first color remaining; and

forming fins of a third color in the gaps.

12. The method of claim 11 , wherein forming fins of the first color comprises:

forming self-assembled fins on a seed layer, the self-assembled fins comprising fins of alternating base materials;

etching away every other self-assembled fin, leaving remaining self-assembled fins having differing heights; and

etching down into a layer of first-color material around the remaining self-assembled fins to form fins of a first color.

13. The method of claim 12 , wherein the fins of the first color each comprise a cap of one or more dielectric layers, with different dielectric layers corresponding to different heights of the fins of the first color.

14. The method of claim 12 , wherein forming self-assembled fins comprises applying a material having two molecular chains of similar or equal length, wherein one of the two molecular chains is attracted to the seed layer.

15. The method of claim 14 , wherein a first chain of the material comprises polystyrene and wherein a second chain of the material comprises poly(methyl methacrylate).

16. The method of claim 12 , further comprising etching the second-color material to a height lower than a height of the tallest remaining self-assembled fins and greater than a height of the shortest remaining self-assembled fins.

17. The method of claim 12 , wherein etching away fins of the first color comprises etching away the fins of the first color having a greater-than-average height.

18. A method of forming a three-color hardmask fin pattern, comprising:

forming fins of a first color on a fin base layer, by:

forming self-assembled fins on a seed layer, the self-assembled fins comprising fins of alternating base materials;

etching away every other self-assembled fin, leaving remaining self-assembled fins having differing heights; and

etching down into a layer of first-color material around the remaining self-assembled fins to form fins of a first color;

depositing a second-color material around the fins of the first color;

etching away fins of the first color, leaving gaps; and

forming fins of a third color in the gaps.

19. The method of claim 18 , further comprising etching the second-color material to a height lower than a height of the tallest remaining self-assembled fins and greater than a height of the shortest remaining self-assembled fins.

20. The method of claim 18 , wherein etching away fins of the first color comprises etching away the fins of the first color having a greater-than-average height.