Common rail contact
A method according to the present disclosure includes receiving a workpiece including a gate structure, a first source/drain (S/D) feature, a second S/D feature, a first dielectric layer over the gate structure, the first S/D feature, the second S/D feature, a first S/D contact over the first S/D feature, a second S/D contact over the second S/D feature, a first etch stop layer (ESL) over the first dielectric layer, and a second dielectric layer over the first ESL, forming a S/D contact via through the second dielectric layer and the first ESL to couple to the first S/D contact, forming a gate contact opening through the second dielectric layer, the first ESL, and the first dielectric layer to expose the gate structure, and forming a common rail opening adjoining the gate contact opening to expose the second S/D contact, and forming a common rail contact in the common rail opening.
1 . A method, comprising:
receiving a workpiece comprising:
a gate structure,
gate spacers disposed along sidewalls of the gate structure,
a first source/drain feature adjacent the gate structure,
a capping layer continuously disposed over the gate structure, the gate spacers and the first source/drain feature,
a first dielectric layer over the capping layer,
a first source/drain contact extending through the first dielectric layer and the capping layer to contact the first source/drain feature,
a first etch stop layer (ESL) over the first dielectric layer and a top surface of the first source/drain contact, and
a second dielectric layer over the first ESL;
forming a gate contact opening through the second dielectric layer, the first ESL, the first dielectric layer, and the capping layer to expose the gate structure;
after the forming of the gate contact opening, forming a first common rail opening adjoining the gate contact opening, wherein the top surface of the first source/drain contact remains covered by a portion of the first ESL;
performing a dry etch process to form a second common rail opening such that the top surface of the first source/drain contact is exposed in the second common rail opening; and
after the performing of the dry etch process, forming a common rail contact in the second common rail opening,
wherein the performing of the dry etch process comprises use of a nitrogen plasma, a hydrogen plasma or a combination thereof.
2 . The method of claim 1 ,
wherein the forming of the first common rail opening comprises forming a patterned mask layer over the workpiece,
wherein a portion of the patterned mask layer remains in the gate contact opening after the first common rail opening is formed.
3 . The method of claim 1 , wherein the performing of the dry etch process forms rounded corners around top edges of the second common rail opening.
4 . The method of claim 1 , wherein, before the dry etch process, a portion of the first dielectric layer is exposed in the first common rail opening.
5 . The method of claim 4 , wherein the performing of the dry etch process forms a middle rounded corner around an edge of the portion of the first dielectric layer.
6 . The method of claim 1 , further comprising:
before the performing of the dry etch process, cleaning the workpiece with a wet clean process.
7 . The method of claim 6 , wherein the wet clean process comprises use of 2-anilino-4-methyl-1,3-thiazole-5-carboxylic acid or isopropyl alcohol (IPA).
8 . A method, comprising:
depositing a capping layer over top surfaces of a gate structure and a bottom dielectric layer over a source/drain feature, the gate structure being disposed over a channel region of an active region, the source/drain feature being disposed over a source/drain region of the active region, the channel region being adjacent the source/drain region;
depositing a first dielectric layer over the capping layer;
forming a source/drain contact through the first dielectric layer, the capping layer, and the bottom dielectric layer to electrically couple to the source/drain feature;
after the forming of the source/drain contact, depositing an etch stop layer (ESL) over the source/drain contact and the first dielectric layer;
depositing a second dielectric layer over the ESL;
forming a gate contact opening through the second dielectric layer, the ESL, the first dielectric layer, and the capping layer to expose the gate structure;
after the forming of the gate contact opening, forming a first common rail opening adjoining the gate contact opening, wherein a top surface of the source/drain contact remains covered by a portion of the ESL;
performing a dry etch process to form a second common rail opening such that the top surface of the source/drain contact is exposed in the second common rail opening; and
after the performing of the dry etch process, forming a common rail contact in the second common rail opening,
wherein the performing of the dry etch process forms rounded corners around top edges of the second common rail opening.
9 . The method of claim 8 , wherein the performing of the dry etch process comprises use of a nitrogen plasma, a hydrogen plasma or a combination thereof.
10 . The method of claim 8 , wherein the forming of the common rail contact comprises:
depositing a glue layer over the second common rail opening to contact the second dielectric layer, the ESL, the first dielectric layer, the capping layer, and the source/drain contact;
depositing a metal fill layer over the glue layer; and
planarizing the glue layer, the metal fill layer and the second dielectric layer such that top surfaces of the glue layer, the metal fill layer and the second dielectric layer are coplanar.
11 . The method of claim 10 , wherein the depositing of the glue layer comprises:
depositing a titanium layer using physical vapor deposition (PVD); and
depositing a titanium nitride layer over the titanium layer using chemical vapor deposition (CVD).
12 . The method of claim 11 ,
wherein the titanium layer comprises a thickness between about 40 Å and about 60 Å,
wherein the titanium nitride layer comprises a thickness between about 10 Å and about 30 Å.
13 . The method of claim 10 , wherein the depositing of the metal fill layer comprises:
depositing a nucleation layer using pulsed chemical vapor deposition (CVD) or atomic layer deposition (ALD); and
depositing a bulk layer over the nucleation layer using CVD.
14 . The method of claim 8 ,
wherein a bottom surface of the first dielectric layer interfaces a top surface of the capping layer,
wherein a bottom surface of the ESL interfaces a top surface of the first dielectric layer,
wherein a bottom surface of the second dielectric layer interfaces a top surface of the ESL.
15 . The method of claim 14 ,
wherein the active region extends lengthwise along a direction,
wherein, along the direction, the common rail contact comprises a first width at the top surface of the ESL and a second width at a top surface of the second dielectric layer,
wherein the first width is between about 48 nm and about 54 nm,
wherein the second width is between about 43 nm and about 78 nm.
16 . The method of claim 8 ,
wherein the forming of the first common rail opening comprises forming a patterned mask layer over the workpiece,
wherein a portion of the patterned mask layer remains in the gate contact opening after the first common rail opening is formed.
17 . A method, comprising:
receiving a workpiece comprising:
a gate structure,
a first source/drain feature adjacent the gate structure,
a capping layer continuously disposed over and in contact with the gate structure and the first source/drain feature,
a first dielectric layer over the capping layer,
a first source/drain contact extending through the first dielectric layer and the capping layer to contact the first source/drain feature,
a first etch stop layer (ESL) over the first dielectric layer and a top surface of the first source/drain contact, and
a second dielectric layer over the first ESL;
forming a gate contact opening through the second dielectric layer, the first ESL, the first dielectric layer, and the capping layer to expose the gate structure;
after the forming of the gate contact opening, forming a patterned mask layer over the workpiece, the patterned mask layer comprising a mask opening directly over the gate contact opening and the first source/drain contact;
etching the second dielectric layer and the first ESL through the mask opening to form a common rail opening adjoining the gate contact opening, wherein the top surface of the first source/drain contact remains covered by a portion of the first ESL;
with the portion of the first ESL covering the first source/drain contact, removing the patterned mask layer using ashing or a wet clean process;
removing the portion of the first ESL to expose the first source/drain contact;
after the removing the portion of the first ESL, depositing a titanium layer over the common rail opening using physical vapor deposition (PVD);
depositing a titanium nitride layer over the titanium layer using chemical vapor deposition (CVD);
depositing a nucleation layer over the titanium layer using pulsed CVD or atomic layer deposition (ALD); and
depositing a bulk layer over the nucleation layer using CVD.
18 . The method of claim 17 , wherein a total thickness of the titanium layer and the titanium nitride layer is between about 0.3 nm and about 1.7 nm.
19 . The method of claim 17 , wherein, after the depositing of the titanium layer, the titanium layer is in contact with the second dielectric layer, the first ESL, the first dielectric layer, and the capping layer.
20 . The method of claim 17 , wherein the depositing of the nucleation layer and the depositing of the bulk layer comprise use of tungsten hexafluoride (WF 6 ) or tungsten hexachloride (WCl 6 ).