Airgap spacers formed in conjunction with a late gate cut
Methods of forming a field-effect transistor and structures for a field effect-transistor. A sidewall spacer is formed adjacent to a sidewall of a gate structure of the field-effect transistor and a dielectric cap is formed over the gate structure and the sidewall spacer. A cut is formed that extends through the dielectric cap, the gate structure, and the sidewall spacer. After forming the cut, the sidewall spacer is removed from beneath the dielectric cap to define a cavity, and a dielectric material is deposited in the cut and in the cavity. The dielectric material encapsulates a portion of the cavity to define an airgap spacer.
1. A method comprising:
forming a gate structure having a sidewall;
forming a sidewall spacer adjacent to the sidewall of the gate structure;
forming a self-aligned contact cap over the gate structure and the sidewall spacer;
forming a cut extending through the self-aligned contact cap, the gate structure, and the sidewall spacer;
after forming the cut, removing the sidewall spacer from beneath the self-aligned contact cap to define a cavity; and
depositing a first dielectric material in the cut and in the cavity,
wherein the first dielectric material encapsulates a portion of the cavity to define an airgap spacer.
2. The method of claim 1 wherein the gate structure overlaps with a first plurality of fins, the cavity extends from the cut parallel to the sidewall of the gate structure, and the cavity is arranged over and between the first plurality of fins.
3. The method of claim 2 wherein the gate structure further overlaps with a second plurality of fins, the cut is arranged between the first plurality of fins and the second plurality of fins, and the cavity is arranged over and between the second plurality of fins.
4. The method of claim 2 wherein a plurality of trench isolation regions surround respective bottom sections of the first plurality of fins, and the cavity extends in a vertical direction from the plurality of trench isolation regions to a bottom surface of the self-aligned contact cap.
5. The method of claim 1 further comprising:
forming an epitaxial semiconductor layer adjacent to the sidewall spacer; and
forming a contact connected with the epitaxial semiconductor layer,
wherein the cavity is arranged between the gate structure and the contact.
6. The method of claim 5 wherein the contact is formed before removing the sidewall spacer.
7. The method of claim 5 wherein the cavity extends from the sidewall of the gate structure to the contact.
8. The method of claim 1 wherein forming the dielectric self-aligned contact cap over the gate structure and the sidewall spacer comprises:
recessing the gate structure;
after recessing the gate structure, recessing the sidewall spacer; and
after recessing the gate structure, depositing a second dielectric material over the gate structure and the sidewall spacer to form the self-aligned contact cap.
9. The method of claim 1 wherein forming the cut extending through the self-aligned contact cap, the gate structure, and the sidewall spacer comprises:
applying an etch mask with an opening over respective portions of self-aligned contact cap, the gate structure, and the sidewall spacer; and
etching the portions of the self-aligned contact cap, the gate structure, and the sidewall spacer through the opening in the etch mask.
10. The method of claim 1 wherein the sidewall spacer is removed from beneath the self-aligned contact cap by an isotropic etching process.
11. The method of claim 1 wherein removing the sidewall spacer from beneath the self-aligned contact cap to define the cavity comprises:
laterally recessing the sidewall spacer outward from the cut beneath the self-aligned contact cap.
12. The method of claim 11 wherein the sidewall spacer is laterally recessed by an isotropic etching process.
13. The method of claim 1 wherein the cut is arranged transverse to the sidewall spacer and to the gate structure.
14. The method of claim 1 wherein the sidewall spacer is fully removed from beneath the self-aligned contact cap.
15. The method of claim 1 wherein the first dielectric material is deposited in the cut and in the cavity by a single deposition process.
16. The method of claim 1 wherein the sidewall spacer is comprised of aluminum oxide or titanium oxide, and the self-aligned contact cap is comprised of silicon nitride.
17. The method of claim 1 wherein the sidewall spacer is comprised of titanium oxide, and the self-aligned contact cap is comprised of silicon nitride.
18. The method of claim 1 wherein the dielectric material pinches off inside the cavity to encapsulate the portion of the cavity and define the airgap spacer.
19. The method of claim 1 wherein the first dielectric material in the cut closes the portion of the cavity to define the airgap spacer.
20. A structure comprising:
a gate structure including a first section and a second section separated from the first section by a cut;
a self-aligned contact cap over the gate structure;
an airgap spacer adjacent to a sidewall of the first section of the gate structure and below the self-aligned contact cap, the airgap spacer including a first portion of a dielectric material and a cavity encapsulated within the first portion of the dielectric material; and
a dielectric pillar arranged in the cut between the first section of the gate structure and the second section of the gate structure, the dielectric pillar comprised of a second portion of the dielectric material that is contiguous with the first portion of the dielectric material.