Fin end spacer for preventing merger of raised active regions
After formation of gate structures over semiconductor fins and prior to formation of raised active regions, a directional ion beam is employed to form a dielectric material portion on end walls of semiconductor fins that are perpendicular to the lengthwise direction of the semiconductor fins. The angle of the directional ion beam is selected to be with a vertical plane including the lengthwise direction of the semiconductor fins, thereby avoiding formation of the dielectric material portion on lengthwise sidewalls of the semiconductor fins. Selective epitaxy of semiconductor material is performed to grow raised active regions from sidewall surfaces of the semiconductor fins. Optionally, horizontal portions of the dielectric material portion may be removed prior to the selective epitaxy process. Further, the dielectric material portion may optionally be removed after the selective epitaxy process.
1. A method of forming a semiconductor structure comprising:
forming a semiconductor fin on a substrate, said semiconductor fin including a pair of lengthwise sidewalls and a widthwise sidewall;
forming a dielectric material portion in direct physical contact with said widthwise sidewall of said semiconductor fin employing a directional ion beam that impinges on said widthwise sidewall along a beam direction that is contained within a vertical plane parallel to said pair of lengthwise sidewalls; and
forming at least one raised active region on physically exposed semiconductor surfaces of said semiconductor fin while said dielectric material portion is present on said widthwise sidewall.
2. The method of claim 1 , wherein said directional ion beam includes ions of a dielectric material, and said dielectric material portion includes a deposited portion of said dielectric material.
3. The method of claim 1 , wherein said directional ion beam includes ions of a cluster of oxygen atoms or ions of a cluster of nitrogen atoms.
4. The method of claim 3 , wherein said dielectric material portion is formed by conversion of a surface portion of said semiconductor fin at said widthwise sidewall into a dielectric material.
5. The method of claim 1 , further comprising forming a gate structure across said semiconductor fin, wherein a contiguous dielectric material layer containing said dielectric material portion is formed on a top surface of said semiconductor fin and a top surface and a sidewall of said gate structure.
6. The method of claim 5 , further comprising removing horizontal portions of said contiguous dielectric material layer by an anisotropic etch, wherein a remaining portion of said contiguous dielectric material layer includes said dielectric material portion and a gate spacer formed on said sidewall of said gate structure.
7. The method of claim 1 , wherein said directional ion beam deposits, on said pair of lengthwise sidewalls, no material, or lesser amount of than on said widthwise sidewall.
8. The method of claim 1 , wherein said forming said semiconductor fin comprises patterning an upper semiconductor material portion of a bulk semiconductor substrate.
9. The method of claim 1 , wherein said forming said semiconductor fin comprises patterning an upper semiconductor layer of a semiconductor-on-insulator substrate, and said substrate comprises at least a buried insulating layer of said semiconductor-on-insulator substrate.
10. The method of claim 1 , further comprising forming a shallow trench isolation layer at the footprint of said semiconductor fin.
11. The method of claim 1 , wherein said forming at least one raised active region comprises selective deposition of a semiconductor material.
12. The method of claim 11 , wherein said selective deposition is a selective epitaxy process, and said semiconductor material does not grow from said dielectric material portion during said selective epitaxy process.
13. The method of claim 11 , wherein said semiconductor material is a same semiconductor material as said semiconductor fin.
14. The method of claim 11 , wherein said semiconductor material is a different semiconductor material than said semiconductor fin.
15. The method of claim 11 , wherein said at least one raised active region contains crystallographic facets.
16. The method of claim 1 , further comprising forming a contact level dielectric layer over said semiconductor fins, said dielectric material portion and said at least one raised active region.