Single fin cut employing angled processing methods
Fin-defining spacers are formed on an array of mandrel structure. Mask material portions can be directionally deposited on fin-defining spacers located on one side of each mandrel structure, while not deposited on the other side. A photoresist layer is subsequently applied and patterned to form an opening, of which the overlay tolerance increases by a pitch of fin-defining spacers due to the mask material portions. Alternately, a conformal silicon oxide layer can be deposited on fin-defining spacers and structure-damaging ion implantation is performed only on fin-defining spacers located on one side of each mandrel structure. A photoresist layer is subsequently applied and patterned to form an opening, from which a damaged silicon oxide portion and an underlying fin-defining spacer are removed, while undamaged silicon oxide portions are not removed. An array of semiconductor fins including a vacancy can be formed by transferring the pattern into a semiconductor layer.
1. A method of forming a semiconductor structure comprising:
forming mandrel structures over a stack of a semiconductor layer and a dielectric layer;
forming fin-defining spacers on sidewalls of said mandrel structures;
forming mask material portions on first fin-defining spacer portions located on a first-side sidewall of each mandrel structure by a directional deposition of a mask material, wherein said mandrel structures shield second fin-defining spacer portions located on a second-side sidewall of each mandrel structure from said mask material during said directional deposition;
forming a patterned mask layer including at least one opening therein over said mandrel structures, fin-defining spacers, and said mask material portions; and
removing portions of said fin-defining spacers located within said at least one opening and not covered by said mask material portions in an anisotropic etch, while a subset of said mask material portions within said at least one opening protects underlying portions of said fin-defining spacers during said anisotropic etch.
2. The method of claim 1 , further comprising etching said stack of said semiconductor layer and said dielectric layer in a second anisotropic etch employing remaining portions of said fin-defining spacers as an etch mask after said removing of said portions of said fin-defining spacers.
3. The method of claim 2 , further comprising:
removing said patterned mask layer and said mask material portions selective to said remaining portions of said fin-defining spacers; and
removing said mandrel structures selective to said remaining portions of said fin-defining spacers prior to said second anisotropic etch.
4. The method of claim 2 , wherein vertical stacks of a semiconductor fin and a dielectric fin are formed by said second anisotropic etch underneath said remaining portions of said fin-defining spacers, and said method further comprises removing said remaining portions of said fin-defining spacers after formation of said vertical stacks.
5. The method of claim 1 , wherein topmost portions of said fin-defining spacers are vertically recessed from top surfaces of said mandrel structures upon formation of said fin-defining spacers.
6. The method of claim 1 , wherein each of said fin-defining spacers are formed as a structure that laterally surrounds one of said mandrel structures and having a uniform thickness at bottom portions thereof.
7. The method of claim 1 , wherein at least one of said mask material portions does not extend to a top surface of said dielectric layer.
8. The method of claim 1 , wherein said directional deposition is performed along a beam direction at a non-zero angle relative to a surface normal of said dielectric layer.
9. The method of claim 8 , wherein said mandrel structures have parallel vertical sidewalls, and said beam direction is within a two-dimensional plane including said surface normal of said dielectric layer and a surface normal of said parallel vertical sidewalls.
10. The method of claim 1 , wherein said mandrel structures have parallel vertical sidewalls, and said mandrel structures constitute a one-dimensional array of mandrel structures having a pitch along a direction perpendicular to said parallel vertical sidewalls.
11. A method of forming a semiconductor structure comprising:
forming mandrel structures over a stack of a semiconductor layer and a dielectric layer;
forming fin-defining spacers on sidewalls of said mandrel structures;
forming a contiguous oxide layer on said fin-defining spacers, said mandrel structures, and said dielectric layer;
forming structurally-damaged oxide portions on first portions of said fin-defining spacers by implanting ions into portions of said contiguous oxide layer employing a directional ion implantation, wherein said mandrel structures shield second portions of said fin-defining spacers from said ions during said directional ion implantation;
forming a patterned mask layer including at least one opening therein over structurally-damaged oxide portions and unimplanted portions of said contiguous oxide layer; and
removing a subset of said structurally-damaged oxide portions from within said at least one opening, while said unimplanted portions of said contiguous oxide layer protect underlying portions of said fin-defining spacers within said at least one opening.
12. The method of claim 11 , further comprising removing physically exposed fin-defining spacers from within said at least one opening selective to said unimplanted portions of said contiguous oxide layer after said removing of said subset of said structurally-damaged oxide portions.
13. The method of claim 12 , further comprising etching said stack of said semiconductor layer and said dielectric layer in an anisotropic etch employing remaining portions of said fin-defining spacers as an etch mask after said removing of said physically exposed fin-defining spacers.
14. The method of claim 13 , further comprising:
removing said patterned mask layer, said structurally-damaged oxide portions, and said unimplanted portions of said contiguous oxide layer selective to said remaining portions of said fin-defining spacers; and
removing said mandrel structures selective to said remaining portions of said fin-defining spacers prior to said anisotropic etch.
15. The method of claim 13 , wherein vertical stacks of a semiconductor fin and a dielectric fin are formed by said anisotropic etch underneath said remaining portions of said fin-defining spacers, and said method further comprises removing said remaining portions of said fin-defining spacers after formation of said vertical stacks.
16. The method of claim 11 , wherein topmost portions of said fin-defining spacers are vertically recessed from top surfaces of said mandrel structures upon formation of said fin-defining spacers.
17. The method of claim 11 , wherein each of said fin-defining spacers are formed as a structure that laterally surrounds one of said mandrel structures and having a uniform thickness at bottom portions thereof.
18. The method of claim 11 , further comprising forming a dielectric spacer around each of said mandrel structures prior to forming said fin-defining spacers.
19. The method of claim 11 , wherein said directional ion implantation is performed along a beam direction at a non-zero angle relative to a surface normal of said dielectric layer.
20. The method of claim 19 , wherein said mandrel structures have parallel vertical sidewalls, and said beam direction is within a two-dimensional plane including said surface normal of said dielectric layer and a surface normal of said parallel vertical sidewalls.