Method and structure for enabling high aspect ratio sacrificial gates
Sacrificial gate structures having an aspect ratio of greater than 5:1 are formed on a substrate. In some embodiments, each sacrificial gate structure straddles a portion of a semiconductor fin that is present on the substrate. An anchoring element is formed orthogonal to each sacrificial gate structure rendering the sacrificial gate structures mechanically stable. After formation of a planarization dielectric layer, each anchoring element can be removed and thereafter each sacrificial gate structure can be replaced with a functional gate structure.
1. A method of forming a semiconductor structure comprising:
forming a sacrificial gate stack over a surface of a substrate;
providing a plurality of hard mask structures on a topmost surface of said sacrificial gate stack, wherein an anchoring element is disposed over segments of each hard mask structure;
patterning said sacrificial gate stack into a plurality of sacrificial gate structures utilizing said plurality of hard mask structures and said anchoring element as an etch mask;
removing each hard mask structure to expose a sacrificial gate cap portion of each sacrificial gate structure, wherein end segments of each sacrificial gate cap portion are connected to a sacrificial gate cap anchoring portion;
forming a dielectric spacer comprising a first dielectric material on sidewalls of each of said sacrificial gate structures and sidewalls of said sacrificial gate cap anchoring portion;
forming a planarization dielectric layer laterally surrounding each of said sacrificial gate structures, wherein said planarization dielectric layer has a topmost surface that is coplanar with a topmost surface of each of said sacrificial gate structures; and
removing each sacrificial gate cap anchoring portion to form a spacer cavity.
2. The method of claim 1 , further comprising forming a second dielectric material in said spacer cavity and along end segments of each sacrificial gate structure, wherein said second dielectric material comprises a different material than the first dielectric material of said dielectric spacer.
3. The method of claim 2 , further comprising removing each of said sacrificial gate structures and replacing the same with a functional gate structure.
4. The method of claim 3 , wherein said removing said sacrificial gate structure comprises a recessed etch.
5. The method of claim 3 , wherein said functional gate structure is formed by depositing a blanket layer of a gate dielectric material; and depositing a blanket layer of a gate conductor material on said blanket layer of gate dielectric material.
6. The method of claim 5 , further comprising depositing a blanket layer of a gate gap material on said blanket layer of gate conductor material.
7. The method of claim 1 , wherein said anchoring element is formed by depositing a layer of a masking material and patterning the layer of masking material by lithography and etching.
8. The method of claim 1 , wherein said forming said sacrificial gate stack comprising first depositing a sacrificial gate dielectric, second depositing a sacrificial gate material on said sacrificial gate dielectric, and third depositing a sacrificial gate cap on said sacrificial gate material.
9. The method of claim 1 , wherein each of said sacrificial gate structure has a height from 50 nm to 200 nm, and a width from 5 nm to 30 nm.
10. The method of claim 1 , wherein said sacrificial gate stack straddles a semiconductor fin that extends upward from a surface of said substrate.
11. The method of claim 1 , wherein said substrate includes at least one semiconductor fin, and said sacrificial gate structure straddles said at least one semiconductor fin.
12. The method of claim 11 , wherein said at least one semiconductor fin is formed by a sidewall image transfer process.
13. The method of claim 11 , wherein said dielectric spacer has a bottommost surface contacting a portion of said at least one semiconductor fin.
14. The method of claim 13 , further comprising forming epitaxial semiconductor material portions on other portions of said at least one semiconductor fin.
15. The method claim 14 , further comprising:
forming a second dielectric material in said spacer cavity and along end segments of each sacrificial gate structure, wherein said second dielectric material comprises a different material than the first dielectric material of said dielectric spacer; and
removing each of said sacrificial gate structures and replacing the same with a functional gate structure.