Method and device related to seamless metal contact
The present disclosure provides a method for semiconductor fabrication. The method includes depositing a first metal layer by a first deposition over a source/drain (S/D) feature and over side portions of a trench exposing the S/D feature. The first metal layer is thicker over the S/D feature than over side portions of the trench. The method includes growing a metal on the first metal layer by a second deposition to form a second metal layer filling up the trench. The second deposition is different from the first deposition and the growing of the metal in a vertical direction is grown at a faster rate than the growing of the metal in a horizontal direction. After growing the metal to form the second metal layer, the method includes planarizing the first and second metal layers to form an S/D contact. The method forms an S/D via on the second metal layer.
1 . A method of forming a semiconductor device, comprising:
receiving a workpiece having gate structures over channel regions on a substrate and source/drain (S/D) features adjacent to the channel regions, the S/D features exposed in trenches between the gate structures;
forming silicide features over the S/D features;
depositing metal cap layers over the workpiece such that the metal cap layers have bottom portions over the silicide features and side portions over sidewalls of the trenches, wherein bottom portions of the metal cap layers are thicker than side portions of the metal cap layers;
depositing a first metal layer over the metal cap layers, the first metal layer comprising tungsten and having bottom and side portions that form over the bottom and side portions of the metal cap layers, respectively, wherein a thickness ratio of the bottom to side portions of the metal cap layers is greater than a thickness ratio of the bottom to side portions of the first metal layer;
growing a second metal layer from the first metal layer to fill up the trenches, wherein metal growth of the second metal layer in a vertical direction is grown at a faster rate than in a horizontal direction;
after the growing of the second metal layer, planarizing the metal cap layers, the first metal layer, and the second metal layer to form S/D contacts; and
forming S/D vias on the second metal layer of the S/D contacts.
2 . The method of claim 1 ,
wherein the depositing of the metal cap layers and the depositing of the first metal layer is performed by physical vapor deposition (PVD),
wherein the growing of the second metal layer is performed by chemical vapor deposition (CVD) or atomic layer deposition (ALD), wherein the CVD or ALD is performed with a metal halide precursor having a metal component and a halogen component, the metal component includes tungsten (W), molybdenum (Mo), or ruthenium (Ru), and the halogen component includes fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).
3 . The method of claim 2 , wherein the growing of the second metal layer includes etching the metal component on side portions of the first metal layer while depositing the metal component over the bottom portions of the first metal layer.
4 . The method of claim 1 , wherein a difference between the thicknesses of the bottom and side portions of the first metal layer is less than a difference between the thicknesses of the bottom and side portions of the metal cap layer.
5 . The method of claim 1 ,
wherein the S/D features include p-type S/D features and n-type S/D features,
wherein the metal cap layers include a first metal cap layer of a first metal material and a second metal cap layer of a second metal material different from the first metal material in composition,
wherein the first metal cap layer is directly over the p-type S/D features and the second metal cap layer is directly over the n-type S/D features, and
wherein the first metal layer is directly on the first and second metal cap layers.
6 . The method of claim 5 , wherein the first metal cap layer includes at least one of nickel, cobalt, and ruthenium and the second metal cap layer includes at least one of zirconium, erbium, and scandium.
7 . The method of claim 1 ,
wherein the S/D features include p-type S/D features and n-type S/D features,
wherein the second metal layer and the metal cap layers directly over the p-type and the n-type S/D features comprise molybdenum.
8 . The method of claim 1 , wherein each of the metal cap layers and the first metal layer are formed of and from a single pure metal without other chemical compounds.
9 . A method of forming a semiconductor device, comprising:
forming a channel regions on a substrate and S/D features adjacent to the channel regions;
forming gate structures over and engaging the channel regions;
forming silicide features over the S/D features;
depositing first metal layers over the silicide features, wherein the first metal layers include horizontal and vertical portions;
depositing a second metal layer over the first metal layers, wherein the second metal layer includes horizontal and vertical portions;
depositing a metal fill layer over the second metal layer such that the metal fill layer is enclosed within the horizontal and vertical portions of the second metal layer;
forming a via extending from the metal fill layer; and
forming a first metal line over the via,
wherein a difference between thicknesses of the horizontal and vertical portions of the second metal layer is less than a difference between thicknesses of the horizontal and vertical portions of the first metal layer,
wherein the S/D features include p-type S/D features and n-type S/D features,
wherein the first metal layers include first metal cap layers of a first metal material and second metal cap layers of a second metal material different from the first metal material in composition,
wherein the first metal cap layers overlay the p-type S/D features and the second metal cap layers overlay n-type S/D features, and
wherein the second metal layer is on and interfaces with the first and second metal cap layers.
10 . The method of claim 9 , wherein a thickness ratio of the horizontal to vertical portions of the first metal layer is greater than a thickness ratio of the horizontal to vertical portions of the second metal layer.
11 . The method of claim 9 ,
wherein the via includes sidewall barrier layers and a via fill metal between the sidewall barrier layers,
wherein the sidewall barrier layers include silicon nitride, and the via fill metal includes the same material as the metal fill layer.
12 . A method of forming a semiconductor device, comprising:
receiving a workpiece having gate structures over channel regions on a substrate and a source/drain (S/D) feature adjacent to one of the channel regions, the S/D feature exposed in a trench between two of the gate structures;
depositing a first metal layer by a first deposition over the S/D feature and over side portions of the trench, wherein the first metal layer is thicker over the S/D feature than over side portions of the trench;
depositing a second metal layer over the first metal layer by a second deposition, the second metal layer having bottom and side portions that form over bottom and side portions of the first metal layer;
growing a metal fill layer on the second metal layer by a third deposition to form a third metal layer that fills up the trench, wherein the third deposition is different from the first deposition and wherein the growing of the metal fill layer in a vertical direction is grown at a faster rate than the growing of the metal fill layer in a horizontal direction; and
after the growing of the metal fill layer, planarizing the first, second, and third metal layers to form an S/D contact,
wherein the first metal layer and the second metal layer have different metal compositions, the first metal layer and the third metal layer have a same metal composition, and the first metal layer and the third metal layer are physically separated from each other by the second metal layer.
13 . The method of claim 12 , further comprising forming an S/D via on the third metal layer of the S/D contact.
14 . The method of claim 12 , The method of claim 1 , wherein before the depositing of the first metal layer, further comprising forming a silicide feature over the S/D feature.
15 . The method of claim 12 , wherein the growing of the metal fill layer includes applying a precursor with an etch chemical that etches the metal fill layer on side portions of the second metal layer while depositing the metal fill layer over the bottom portions of the second metal layer.
16 . The method of claim 12 ,
wherein the first deposition and the second deposition are performed by physical vapor deposition (PVD),
wherein the third deposition is performed by chemical vapor deposition (CVD) or atomic layer deposition (ALD), the CVD or ALD is performed with a metal halide precursor having a metal component and a halogen component, the metal component includes tungsten (W), molybdenum (Mo), ruthenium (Ru), cobalt (Co), iridium (Ir), or rhodium (Rh), and the halogen component includes fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).
17 . The method of claim 16 , wherein a concentration of the halogen component remains in the metal fill layer after the metal fill layer is formed, and a concentration of the halogen component at an interface between the second metal layer and metal fill layer is greater than a concentration of the halogen component in other portions of the metal fill layer.
18 . The method of claim 12 , wherein the first metal layer and the second metal layer include different metals.
19 . The method of claim 12 ,
wherein a bottom portion of the first metal layer has a first thickness, a bottom portion of the second metal layer has a second thickness, and the first thickness is greater than the second thickness,
wherein the bottom and side portions of the second metal layer have a substantially same thickness.
20 . The method of claim 12 , wherein the first metal layer includes molybdenum (Mo), the second metal layer includes tungsten (W), and the metal fill layer includes (Mo).