Conductive structures and methods of forming the same
Depositing a seed layer after formation of the MD in order to reduce or prevent epitaxial growth of the seed layer toward the MD. For example, the seed layer may be deposited using CVD and conformal dry etching. In some implementations, the seed layer may be formed of ruthenium (Ru), molybdenum (Mo), or tungsten (W). Accordingly, the seed layer helps reduce or prevent seam formation in the VG, which reduces resistance of the VG by allowing for bottom-up metal growth. Additionally, current leakage from the VG to the MD is reduced or even prevented. As a result, device performance and efficiency are increased and breakdown voltage of the gate structure is also increased. Additionally, because electrical shorts are less likely, yield is increased, which conserves power, raw materials, and processing resources that otherwise would have been consumed during manufacture.
1 . A method, comprising:
forming a recess in at least one dielectric layer and adjacent to a source/drain structure,
wherein the recess exposes a portion of a top surface of a gate structure, and
wherein the recess is formed through an etch stop layer (ESL) that is on the top surface of the gate structure;
forming a seed layer within the recess using conformal chemical vapor deposition (CVD), wherein the seed layer comprises a metal;
etching the seed layer from part of sidewalls of the recess, wherein a remaining seed layer is over a bottom surface of the recess; and
forming a gate via within the recess and over the remaining seed layer,
wherein a top surface of the remaining seed layer is higher than a top surface of the ESL, and
wherein a portion of the ESL is on a side surface of the remaining seed layer.
2 . The method of claim 1 ,
wherein the seed layer is selected from ruthenium, molybdenum, tungsten, or a combination thereof.
3 . The method of claim 1 ,
wherein forming the seed layer comprises:
performing CVD with a precursor selected from a ruthenium dodecacarbonyl, a molybdenum chloride, a tungsten fluoride, or a combination thereof.
4 . The method of claim 1 ,
wherein forming the seed layer comprises:
performing CVD with a co-reactant selected from carbon monoxide, a cyclohexanedione, silane, or a combination thereof.
5 . The method of claim 1 ,
wherein forming the seed layer comprises:
performing CVD at a temperature in a range from approximately 150 degrees Celsius (° C.) to approximately 450° C.
6 . The method of claim 1 ,
wherein forming the seed layer comprises:
performing CVD at a pressure in a range from approximately 0.005 Torr to approximately 50 Torr.
7 . The method of claim 1 ,
wherein the gate via is formed of a material selected from ruthenium, molybdenum, tungsten, aluminum, titanium, titanium nitride, copper, cobalt, or a combination thereof.
8 . The method of claim 1 ,
wherein etching the seed layer comprises:
using a chlorine or ozone plasma to remove the seed layer from the part of the sidewalls of the recess,
wherein a height of the remaining seed layer is reduced by the etching.
9 . The method of claim 1 , further comprising:
performing a chemical mechanical planarization on a gate structure below the gate via; and
forming the source/drain structure before forming the seed layer.
10 . The method of claim 1 , further comprising:
performing a chemical mechanical planarization on the gate via.
11 . The method of claim 1 , wherein the remaining seed layer contacts the portion of the top surface of a gate structure.
12 . A method, comprising:
forming a plurality of recesses in at least one dielectric layer and adjacent to a source/drain structure;
forming a seed layer within the recesses using conformal chemical vapor deposition (CVD) with a precursor selected from a ruthenium dodecacarbonyl, a molybdenum chloride, a tungsten fluoride, or a combination thereof;
etching the seed layer from part of sidewalls of the recesses, wherein remaining portions of the seed layer are over bottom surfaces of the recesses; and
forming gate vias within the recesses and over the remaining seed layer,
wherein a first recess of the plurality of recesses exposes a portion of a top surface of a first gate structure,
wherein a second recess of the plurality of recesses exposes a portion of a top surface of a second gate structure,
wherein the first recess and the second recess are formed through an etch stop layer (ESL) that is on the top surface of the first gate structure and the top surface of the second gate structure,
wherein top surfaces of the remaining portions of the seed layer are higher than a top surface of the ESL, and
wherein portions of the ESL are on side surfaces of the remaining portions of the seed layer.
13 . The method of claim 12 ,
wherein forming the seed layer comprises:
performing CVD with a co-reactant selected from carbon monoxide, a cyclohexanedione, silane, or a combination thereof.
14 . The method of claim 12 ,
wherein forming the seed layer comprises:
performing CVD at a temperature in a range from approximately 150 degrees Celsius (C) to approximately 450° C.
15 . The method of claim 12 ,
wherein forming the seed layer comprises:
performing CVD at a pressure in a range from approximately 0.005 Torr to approximately 50 Torr.
16 . A method, comprising:
forming a gate structure adjacent to a source/drain structure;
forming a seed layer over the gate structure; and
forming a gate via over the seed layer and electrically connected to the gate structure through the seed layer,
wherein a bottom surface of the gate via has a width approximately equal to a width of a top surface of the seed layer, and the top surface of the seed layer is level with the bottom surface of the gate via,
wherein the seed layer is formed through an etch stop layer (ESL) that is on a top surface of the gate structure,
wherein a top surface of the seed layer is higher than a top surface of the ESL, and
wherein a portion of the ESL is on a side surface of the seed layer.
17 . The method of claim 16 ,
wherein forming the seed layer comprises:
forming the seed layer within a recess; and
etching the seed layer from part of sidewalls of the recess, wherein a remainder of the seed layer is over a bottom surface of the recess.
18 . The method of claim 16 ,
wherein the seed layer is formed using conformal chemical vapor deposition (CVD).
19 . The method of claim 18 ,
wherein the seed layer comprises a metal.
20 . The method of claim 18 ,
wherein the conformal CVD is performed with a precursor selected from a ruthenium dodecacarbonyl, a molybdenum chloride, or a tungsten fluoride.