Method to align mask patterns
Alignment tolerances between narrow mask lines and wider mask lines in an integrated circuit are increased. The narrow mask lines are formed by pitch multiplication and the wider mask lines are formed by photolithography. The wider mask lines are aligned so that one side of those lines is flush with or inset from a corresponding side of the narrow lines. Being wider, the opposite sides of the wider mask lines protrude beyond the corresponding opposite sides of the narrow mask lines. The wider mask lines are formed in negative photoresist having a height less than the height of the narrow mask lines. The narrow mask lines can prevent expansion of the mask lines in one direction, thus increasing alignment tolerances in that direction. In the other direction, a shadowing effect causes the wider mask lines to be formed with a rounded corner, thus increasing alignment tolerances in that direction.
1. A method for semiconductor processing, comprising:
providing spacers overlying a substrate, each of the spacers having a long side;
providing a photodefinable layer around the spacers; and
patterning by photolithograhy mask features in the photodefinable layer, each of the mask features having a long side, wherein each of the mask features and the spacers are aligned with the long side of the mask feature inset from the corresponding long side of a spacer such that the long side of the mask feature does not extend beyond the long side of the spacer.
2. The method of claim 1 , wherein providing spacers comprises:
providing a plurality of loops of spacer material; and
etching ends of the spacer loops to form the spacers.
3. The method of claim 2 , wherein providing the plurality of loops comprises:
providing each of the loops extending around a sidewall of each of a plurality of mandrels; and
selectively removing the mandrels relative to the loops.
4. The method of claim 3 , wherein providing each of the loops extending around a sidewall of each of a plurality of mandrels comprises:
blanket depositing the spacer material on the mandrels; and
anisotropically etching the spacer material from horizontal surfaces to define the loops of spacer material around the the sidewall of each of the plurality of mandrels.
5. The method of claim 4 , wherein the mandrels are photolithographically defined.
6. The method of claim 5 , wherein the mandrels are formed by a process comprising:
providing a photodefinable layer over a layer of temporary material;
patterning the photodefinable layer; and
transferring a pattern from the photodefinable layer to the layer of temporary material to form the plurality of mandrels.
7. The method of claim 6 , wherein the mandrels are formed of amorphous carbon.
8. The method of claim 1 , wherein the photodefinable layer is formed of photoresist and wherein patterning mask features comprises overdeveloping photoresist.
9. The method of claim 1 , further comprising:
transferring a pattern defined by the mask features and the spacers to an underlying hardmask layer; and
subsequently transferring a pattern in the hardmask layer to an underlying amorphous carbon layer.
10. The method of claim 9 , further comprising transferring a pattern in the amorphous carbon layer to the substrate.
11. The method of claim 1 , wherein a thickness of the photodefinable layer is about 80% or less of a height of the spacers.
12. The method of claim 1 , further comprising transferring a pattern defined by the mask features and the spacers to the substrate, thereby defining interconnects.
13. The method of claim 1 , wherein the spacers extend in an array region of a partially formed integrated circuit and wherein the mask features extend in a periphery region of the partially formed integrated circuit.
14. A method for semiconductor processing, comprising:
forming a plurality of mandrels by performing photolithography;
forming a plurality of first mask features, each of the first mask features having a first long side, wherein first mask features of the plurality of first mask features are disposed between neighboring pairs of the plurality of mandrels;
depositing a photodefinable layer around the plurality of first mask features; and
patterning by photolithography second mask features in the photodefinable layer, each of the second mask features having a second long side, wherein the second mask features and the first mask features are aligned with the second long side inset from the corresponding first long side such that the second long side does not extend beyond the first long side.
15. The method of claim 14 , further comprising selectively removing the plurality of mandrels after forming the plurality of first mask features.
16. The method of claim 14 , wherein forming the plurality of mandrels comprises:
patterning a photodefinable layer to form a photodefinable layer pattern;
transferring the photodefinable layer pattern to a layer of mandrel material, wherein the plurality of mandrels are formed of mandrel material.
17. The method of claim 16 , wherein forming the plurality of first mask features comprises:
blanket depositing a layer of spacer material on the mandrels; and
anisotropically etching the layer of spacer material to define loops of spacer material around the sidewall of each of the mandrels;
selectively removing the mandrels; and
etching ends of the loops of spacer material to define separated spacers, wherein the separated spacers constitute the plurality of first mask features.
18. The method of claim 14 , wherein a width of each of the second mask features is greater than a width of each of the plurality of first mask features.
19. The method of claim 14 , wherein each of the second mask features span across an entire width of each of the plurality of first mask features.
20. The method of claim 14 , wherein a pitch of the plurality of first mask features is about 100 nm or less.