Multi-gate devices and method of fabricating the same
Provided is a method of manufacturing a semiconductor device including providing a semiconductor substrate, and forming an epitaxial stack on the semiconductor substrate. The epitaxial stack comprises a plurality of first epitaxial layers interposed by a plurality of second epitaxial layers. The method further includes patterning the epitaxial stack and the semiconductor substrate to form a semiconductor fin, recessing a portion of the semiconductor fin to form source/drain spaces; and laterally removing portions of the plurality of first epitaxial layers exposed by the source/drain spaces to form a plurality of cavities. The method further includes forming inner spacers in the plurality of cavities, performing a treatment process to remove an inner spacer residue in the source/drain spaces, forming S/D features in the source/drain spaces, and forming a gate structure engaging the semiconductor fin.
1. A method of manufacturing a semiconductor device, comprising:
providing a semiconductor substrate;
forming an epitaxial stack on the semiconductor substrate, wherein the epitaxial stack comprises a plurality of first epitaxial layers interposed by a plurality of second epitaxial layers;
patterning the epitaxial stack and the semiconductor substrate to form a semiconductor fin;
recessing a portion of the semiconductor fin to form source/drain spaces;
laterally removing portions of the plurality of first epitaxial layers exposed by the source/drain spaces to form a plurality of cavities;
forming inner spacers in the plurality of cavities;
performing a treatment process to remove an inner spacer residue in the source/drain spaces;
forming S/D features in the source/drain spaces; and
forming a gate structure engaging the semiconductor fin,
wherein the performing the treatment process comprises a selectively etching process, and the selectively etching process comprises:
forming a patterned mask layer having an opening, wherein the source/drain spaces are exposed by the opening;
performing an anisotropic process to remove the inner spacer residue; and
removing the patterned mask layer.
2. The method of claim 1 , wherein the semiconductor fin comprises a first fin and a second fin, the first fin has a first width less than a second width of the second fin, and the second fin is covered by the patterned mask layer during the performing the anisotropic process.
3. The method of claim 1 , further comprising:
after the patterning the epitaxial stack and the semiconductor substrate and before the recessing the portion of the semiconductor fin, forming a sacrificial gate structure across the semiconductor fin, and forming first spacers on sidewalls of the sacrificial gate structure and sidewalls of the semiconductor fin;
further removing a portion of the first spacers on the sidewalls of the semiconductor fin to form second spacers during the recessing the portion of the semiconductor fin; and
after the forming S/D features and before the forming the gate structure, removing the sacrificial gate structure.
4. The method of claim 3 , further comprising:
removing the second spacers during the performing the treatment process, thereby exposing an isolation feature under the second spacers.
5. The method of claim 3 , further comprising:
partially removing the second spacers during the performing the treatment process, thereby reducing a height of the second spacers.
6. The method of claim 1 , further comprising:
before the forming the gate structure, removing the plurality of first epitaxial layers to form a plurality of semiconductor nanosheets.
7. The method of claim 1 , further comprising:
before the forming the source/drain (S/D) feature and after the performing the treatment process, performing a cleaning process on the semiconductor substrate.
8. The method of claim 1 , wherein the anisotropic process comprises a dry etching process.
9. A method of manufacturing a multi-gate device, comprising:
providing a semiconductor substrate;
forming a plurality of semiconductor nanosheets on a first portion of the semiconductor substrate;
forming an epitaxial source/drain (S/D) feature on a second portion of the semiconductor substrate, wherein the epitaxial source/drain (S/D) feature is in contact with the plurality of semiconductor nanosheets;
forming a gate structure wrapping each of the plurality of semiconductor nanosheets; and
before the forming the epitaxial source/drain (S/D) feature, performing a treatment process to remove a residue on a surface of the second portion of the semiconductor substrate, wherein the performing the treatment process comprises a selectively etching process.
10. The method of claim 9 , wherein the residue is formed during the forming the plurality of semiconductor nanosheets.
11. The method of claim 9 , wherein the forming a plurality of semiconductor nanosheets comprises:
forming a plurality of first layers interposed by a plurality of second layers on first portion of the semiconductor substrate;
laterally removing portions of the plurality of first layers to form a plurality of cavities;
forming inner spacers in the plurality of cavities; and
removing the first layers,
wherein the residue is formed during the forming inner spacers.
12. The method of claim 9 , wherein the treatment process is performed to further expose a surface of an isolation feature that is formed around the second portion of the semiconductor substrate.
13. The method of claim 9 , wherein the treatment process is performed to further reduce a height of a spacer, and the spacer is formed on an isolation feature around the second portion of the semiconductor substrate.
14. The method of claim 9 , wherein the anisotropic process comprises a dry etching process.
15. The method of claim 9 , further comprising:
before the forming the epitaxial source/drain (S/D) feature, forming a sacrificial gate structure on a first portion of the semiconductor substrate; and
after the forming the epitaxial source/drain (S/D) feature and before the forming the gate structure, removing the sacrificial gate structure.
16. The method of claim 9 , wherein the selectively etching process comprises:
forming a patterned mask layer having an opening, wherein the source/drain spaces are exposed by the opening;
performing an anisotropic etching process; and
removing the patterned mask layer.
17. The method of claim 9 , further comprising:
before the forming the epitaxial source/drain (S/D) feature and after the performing the treatment process, performing a cleaning process on the surface of the second portion of the semiconductor substrate.
18. A semiconductor device, comprising:
a semiconductor substrate;
a plurality of semiconductor nanosheets disposed over a first portion of the semiconductor substrate;
a plurality of source/drain (S/D) features on a second portion of the semiconductor substrate and a butting the plurality of semiconductor nanosheets;
an isolation feature around the second portion of the semiconductor substrate, wherein there is an air gap between the isolation feature and the source/drain (S/D) feature, and a top surface of the isolation feature and a lower facet of the source/drain (S/D) feature are exposed by the air gap;
a gate stack wrapping each of the plurality of semiconductor nanosheets; and
inner spacers interposing between the S/D features and the gate stack,
wherein the second portion of the semiconductor substrate comprises a first fin and a second fin, the first fin has a first width less than a second width of the second fin, and a first surface of the isolation feature around the first fin is lower than a second surface of the isolation feature around the second fin.
19. The semiconductor device of claim 18 , wherein the plurality of source/drain (S/D) features comprise a first source/drain (S/D) feature on the first fin, and a second source/drain (S/D) feature on the second fin, the second source/drain (S/D) feature has a base portion surround by a spacer on the second surface of the isolation feature, and the first source/drain (S/D) feature is free from base portion.
20. The semiconductor device of claim 19 , further comprises a hybrid fin interposed between the first source/drain (S/D) feature and the second source/drain (S/D) feature, and between the first fin and the second fin.