Self-aligned double patterning

1. A method comprising:

patterning a first mandrel layer over a target layer to form first mandrels and second mandrels, the first mandrels having a larger width than the second mandrels;

depositing a spacer layer over the first mandrels and the second mandrels;

forming a mask layer over the spacer layer and the first mandrels;

thinning the spacer layer over the second mandrels;

removing the mask layer;

etching the spacer layer to form a spacer etch mask, the spacer etch mask comprising first spacers in contact with sidewalls of the first mandrels and second spacers in contact with sidewalls of the second mandrels, the first spacers having a greater width than the second spacers; and

etching the target layer based on the spacer etch mask.

2. The method of claim 1 , further comprising:

after removing the mask layer, depositing a second spacer layer over the first spacer layer.

3. The method of claim 1 , further comprising:

forming first metal lines in a first region of the target layer, the first region corresponding to the first mandrels; and

forming second metal lines in a second region of the target layer, the second region corresponding to the second mandrels, the second metal lines being separated from each other by a greater distance than the first metal lines.

4. The method of claim 1 , further comprising:

forming a second mask layer over the spacer layer and the first mandrels;

patterning the second mask layer to expose cut line areas;

depositing a sacrificial material in the cut line areas; and

removing the second mask layer, the sacrificial material becoming part of the spacer etch mask.

5. The method of claim 1 , further comprising:

using the spacer etch mask to etch a hard mask underlying the spacer etch mask; and

using the hard mask to etch the target layer.

6. The method of claim 1 , wherein the first spacers are between 20 Å and 50 Å wider than the second spacers.

7. A method comprising:

patterning a first mandrel layer over a target layer to form first mandrels and second mandrels, the first mandrels having a larger width than the second mandrels;

depositing a spacer layer over the first mandrels and the second mandrels;

forming a mask layer over the spacer layer and the second mandrels, a portion of the spacer layer over the first mandrels exposed from the mask layer;

depositing a pad layer over the mask layer and the exposed spacer layer;

removing the mask layer;

etching the spacer layer and the pad layer over the first mandrels to form a first spacer etch mask comprising first spacers, and etching the spacer layer over the second mandrels to form a second spacer mask comprising second spacers, the first spacers each being wider than the second spacers; and

etching the target layer based on the first spacer etch mask and the second spacer etch mask.

8. The method of claim 7 , further comprising:

after removing the mask layer, forming a second mask layer;

patterning the second mask layer to provide an opening in the second mask layer, the opening exposing residue of the pad layer; and

removing the residue of the pad layer.

9. The method of claim 7 , further comprising:

after removing the mask layer, forming a second mask layer;

patterning the second mask layer to provide one or more openings in the second mask layer, the one or more openings each exposing an area over a subset of the first mandrels or a subset of the second mandrels;

depositing a sacrificial material in the one or more openings; and

removing the second mask layer, thereby leaving pillars of the sacrificial material over the first mandrels or the second mandrels, wherein the first spacer mask or second spacer mask comprises pillars of the sacrificial material.

10. The method of claim 9 , wherein the pad layer and the sacrificial material comprise the same material.

11. The method of claim 7 , wherein the target layer comprises a semiconductor material.

12. The method of claim 7 , wherein patterning the first mandrel layer includes patterning the first mandrel layer to form a hard mask between the first mandrels and the second mandrels.

13. The method of claim 7 , further comprising:

removing horizontal portions of the pad layer from over the first mandrels, remaining vertical portions of the pad layer disposed on sidewalls of the spacer layer.

14. A method comprising:

forming a first set of mandrels in a first region of a wafer;

forming a second set of mandrels in a second region of the wafer, the first set of mandrels having a wider pitch than the second set of mandrels;

depositing a first spacer layer over the first set of mandrels and the second set of mandrels;

depositing a second spacer layer over the first set of mandrels and the second set of mandrels;

forming a mask over the first region;

removing the second spacer layer over the second set of mandrels in the second region;

removing the mask;

etching the first spacer layer in the second region and etching the first spacer layer and the second spacer layer in the first region to form a spacer mask comprising first spacers in the first region and second spacers in the second region, the first spacers being wider than the second spacers;

removing the first set of mandrels and the second set of mandrels; and

etching a target layer underlying the spacer mask.

15. The method of claim 14 , further comprising:

etching a hard mask layer directly underlying the spacer mask and using the hard mask layer to etch the target layer.

16. The method of claim 14 , further comprising:

depositing a liner layer and a conductive fill into openings in the target layer, thereby forming first metal lines in the first region and second metal lines in the second region, wherein spacing between adjacent lines in the first region is greater than spacing between adjacent metal lines in the second region.

17. The method of claim 14 , wherein the second spacer layer comprises a different material than the first spacer layer.

18. The method of claim 14 , further comprising:

forming a hard mask structure in a third region of the wafer, the hard mask structure interposed between one mandrel of the first set of mandrels and one mandrel of the second set of mandrels, wherein a spacer of the first spacers contacts one side of the hard mask and a spacer of the second spacers contacts an opposite side of the hard mask.

19. The method of claim 14 , wherein the first spacers are taller than the second spacers.

20. The method of claim 14 , wherein the first spacers comprise a bottom portion and a first side portion comprising a section of the first spacer layer and a second side portion comprising a section of the second spacer layer.