Source/drain contact structure
A method according to the present disclosure includes receiving a workpiece that includes a gate structure, a first gate spacer feature, a second gate spacer feature, a gate-top dielectric feature over the gate structure, the first gate spacer feature and the second gate spacer feature, a first source/drain feature over a first source/drain region, a second source/drain feature over a second source/drain region, a first dielectric layer over the first source/drain feature, and a second dielectric layer over the second source/drain feature. The method further includes replacing a top portion of the first dielectric layer with a first hard mask layer, forming a second hard mask layer over the first hard mask layer while the second dielectric layer is exposed, etching the second dielectric layer to form a source/drain contact opening and to expose the second source/drain feature, and forming a source/drain contact over the second source/drain feature.
1. A method, comprising:
receiving a workpiece comprising:
a gate structure disposed over a channel region of an active region,
a first gate spacer feature disposed along a first sidewall of the gate structure,
a second gate spacer feature disposed along a second sidewall of the gate structure, the second sidewall opposing the first sidewall,
a gate-top dielectric feature over the gate structure, the first gate spacer feature and the second gate spacer feature,
a first source/drain feature disposed over a first source/drain region of the active region,
a second source/drain feature disposed over a second source/drain region of the active region,
a first dielectric layer over the first source/drain feature, and
a second dielectric layer over the second source/drain feature;
forming a contact cut opening over the first source/drain feature while the second dielectric layer is masked, the contact cut opening displacing a top portion of the first dielectric layer;
depositing a hard mask layer over the workpiece and in the contact cut opening;
after the depositing of the hard mask layer, planarizing the workpiece until a top surface of the hard mask layer is coplanar with a top surface of the second dielectric layer;
forming a source/drain contact opening by removing the second dielectric layer to expose the second source/drain feature; and
forming a source/drain contact in the source/drain contact opening.
2. The method of claim 1 ,
wherein the first dielectric layer and the second dielectric layer comprise silicon oxide,
wherein the first gate spacer feature, and the second gate spacer feature, the gate-top dielectric feature, and the hard mask layer comprise silicon nitride.
3. The method of claim 1 , wherein, after the planarizing of the workpiece, the first source/drain feature underlies the hard mask layer and the first dielectric layer, and the second source/drain feature underlies the second dielectric layer.
4. The method of claim 1 , wherein the workpiece further comprises a contact etch stop layer (CESL) disposed between the first dielectric layer and the first source/drain feature and between the second dielectric layer and the second source/drain feature.
5. The method of claim 1 , wherein the channel region of the active region comprises a fin-like structure.
6. The method of claim 1 , wherein the channel region of the active region comprises a vertical stack of nanostructures and the gate structure wraps around each of the vertical stack of nanostructures.
7. The method of claim 1 , wherein a composition of the hard mask layer is different from a composition of the second dielectric layer.
8. The method of claim 1 , wherein, after the planarizing of the workpiece, the top surface of the hard mask layer is coplanar with a top surface of the gate-top dielectric feature.
9. The method of claim 1 , wherein the forming of the source/drain contact opening comprises:
depositing a top dielectric layer over the workpiece;
depositing a tungsten carbide layer over the top dielectric layer;
forming an access opening through the tungsten carbide layer, the access opening being over the hard mask layer and the second dielectric layer; and
selectively etching the second dielectric layer.
10. A method, comprising:
receiving a workpiece comprising:
a gate structure disposed over a channel region of an active region,
a first gate spacer feature disposed along a first sidewall of the gate structure,
a second gate spacer feature disposed along a second sidewall of the gate structure, the second sidewall opposing the first sidewall,
a gate-top dielectric feature over the gate structure, the first gate spacer feature and the second gate spacer feature,
a first source/drain feature disposed over a first source/drain region of the active region,
a second source/drain feature disposed over a second source/drain region of the active region,
a first dielectric layer over the first source/drain feature, and
a second dielectric layer over the second source/drain feature;
replacing a top portion of the first dielectric layer with a hard mask layer, wherein the hard mask layer spans at least an entire width of the first source/drain feature;
selectively etching the second dielectric layer to form a source/drain contact opening and to expose the second source/drain feature; and
after the selectively etching of the second dielectric layer, forming a source/drain contact over the second source/drain feature.
11. The method of claim 10 ,
wherein the first dielectric layer and the second dielectric layer comprise silicon oxide,
wherein the first gate spacer feature, and the second gate spacer feature, the gate-top dielectric feature, and the hard mask layer comprise silicon nitride.
12. The method of claim 10 , wherein the replacing comprises:
forming a contact cut opening over the first source/drain feature while the second dielectric layer is masked, the contact cut opening displacing the top portion of the first dielectric layer;
depositing the hard mask layer over the contact cut opening; and
planarizing the workpiece until a top surface of the hard mask layer is coplanar with a top surface of the second dielectric layer.
13. The method of claim 10 , wherein a composition of the hard mask layer is different from a composition of the second dielectric layer.
14. The method of claim 10 , wherein the forming of the source/drain contact comprises:
forming a silicide layer over the workpiece and on the second source/drain feature;
depositing a metal fill layer over the silicide layer; and
planarizing the workpiece until a top surface of the metal fill layer is coplanar with a top surface of the hard mask layer.
15. The method of claim 10 , wherein the selectively etching comprises:
depositing a top dielectric layer over the workpiece;
depositing a tungsten carbide layer over the top dielectric layer;
forming an access opening through the tungsten carbide layer, the access opening being over the hard mask layer and the second dielectric layer; and
selectively etching the second dielectric layer.
16. A method, comprising:
receiving a workpiece comprising:
a first source/drain feature over a first source/drain region,
a second source/drain feature over a second source/drain region,
a gate structure over a channel region disposed between the first and second source/drain regions,
a gate-top dielectric feature over the gate structure,
a first dielectric layer over the first source/drain feature, and
a second dielectric layer over the second source/drain feature;
selectively recessing a top portion of the first dielectric layer, wherein the selectively recessing includes forming a contact cut opening over the first source/drain feature while the second dielectric layer is masked, the contact cut opening displacing the top portion of the first dielectric layer;
depositing a hard mask layer over the first and second dielectric layers such that the hard mask layer fills the recessed top portion of the first dielectric layer;
planarizing the workpiece such that a top surface of the hard mask layer and a top surface of the second dielectric layer are coplanar;
depositing a third dielectric layer over the hard mask layer and the second dielectric layer;
forming an access opening partially through the third dielectric layer;
after the forming of the access opening, forming a source/drain contact opening through the second dielectric layer to expose the second source/drain feature; and
forming a source/drain contact in the source/drain contact opening.
17. The method of claim 16 , wherein the workpiece further comprises a first gate spacer along a sidewall of the first dielectric layer and a second gate spacer along a sidewall of the second dielectric layer, wherein the gate-top dielectric feature is further disposed over top and side surfaces of the first and second gate spacers.
18. The method of claim 16 , wherein the workpiece further comprises a contact etch stop layer (CESL) disposed between the first dielectric layer and the first source/drain feature and between the second dielectric layer and the second source/drain feature.
19. The method of claim 17 ,
wherein the first dielectric layer and the second dielectric layer comprise silicon oxide,
wherein the first gate spacer, and the second gate spacer, the gate-top dielectric feature, and the hard mask layer comprise silicon nitride.
20. The method of claim 17 , wherein the forming of the source/drain contact comprises:
depositing a metal liner over the workpiece;
forming a silicide layer over the workpiece and on the second source/drain feature;
depositing a metal fill layer over the silicide layer; and
planarizing the workpiece until a top surface of the metal fill layer is coplanar with the top surface of the hard mask layer.