Integrated circuit devices including backside power rail and methods of forming the same
Methods of forming an integrated circuit devices may include providing first and second active regions, an isolation layer, and first and second sacrificial stack structures. The first and second sacrificial stack structures may contact the first and second active regions, and the first and second sacrificial stack structures may each include a channel layer and a sacrificial layer. The methods may also include forming an etch stop layer on the isolation layer, replacing portions of the first and second sacrificial stack structures with first and second source/drain regions, forming a front contact including a front contact plug, forming a back-side insulator, and forming a back contact plug in the isolation layer and the back-side insulator. At least one of a portion of the front contact plug and a portion of the back contact plug may be in the etch stop layer.
1 . A method of forming an integrated circuit device, the method comprising:
providing a substrate that comprises a front surface and a back surface opposite the front surface, wherein first and second active regions, an isolation layer, and first and second sacrificial stack structures are provided on the front surface of the substrate, and wherein the isolation layer is between the first and second active regions, the first and second sacrificial stack structures respectively contact upper surfaces of the first and second active regions, and the first and second sacrificial stack structures each comprise a channel layer and a sacrificial layer;
forming an etch stop layer on an upper surface of the isolation layer;
replacing portions of the first and second sacrificial stack structures with first and second source/drain regions, respectively;
forming a front contact that contacts the first source/drain region, wherein the front contact comprises a front contact plug that is between the first and second source/drain regions;
forming a back-side insulator on a lower surface of the isolation layer; and
forming a back contact plug that is in the isolation layer and the back-side insulator and contacts a lower surface of the front contact plug,
wherein at least one of a portion of the front contact plug and a portion of the back contact plug is in the etch stop layer.
2 . The method of claim 1 , wherein forming the etch stop layer comprises:
forming a preliminary etch stop layer on the first and second sacrificial stack structures and the isolation layer;
forming a preliminary filler layer on the preliminary etch stop layer;
etching the preliminary filler layer, thereby forming a filler layer between the first and second sacrificial stack structures on the preliminary etch stop layer, wherein a portion of the preliminary etch stop layer and portions of the first and second sacrificial stack structures protrude upwardly beyond an upper surface of the filler layer; and then
etching the preliminary etch stop layer, thereby forming the etch stop layer and exposing side surfaces of the first and second sacrificial stack structures.
3 . The method of claim 1 , wherein forming the front contact comprises:
forming a first insulator on the first and second source/drain regions and the etch stop layer;
etching the first insulator and the etch stop layer, thereby forming a first opening in the first insulator, wherein the first opening exposes the etch stop layer; and
forming the front contact plug in the first opening.
4 . The method of claim 1 , further comprising forming a source/drain contact that contacts the second source/drain region,
wherein forming the front contact and the source/drain contact comprises:
forming a first insulator on the first and second source/drain regions and the etch stop layer;
etching the first insulator and the etch stop layer, thereby forming first and second openings in the first insulator, wherein the first and second openings expose the first and second source/drain regions, respectively, and the first opening further exposes the etch stop layer;
forming a conductive layer in the first and second openings and on the first insulator; and
removing the conductive layer until the first insulator is exposed, thereby forming the front contact in the first opening and forming the source/drain contact in the second opening.
5 . The method of claim 1 , wherein forming the back contact plug comprises:
etching the back-side insulator and the isolation layer, thereby forming a back-side opening that is in the back-side insulator and the isolation layer; and
forming the back contact plug in the back-side opening.
6 . The method of claim 5 , wherein forming the back-side opening comprises etching a portion of the etch stop layer.
7 . The method of claim 1 , further comprising forming a back-side power rail,
wherein forming the back contact plug and the back-side power rail comprises:
etching the back-side insulator and the isolation layer, thereby forming a line-shaped opening in the back-side insulator and forming a back-side opening that is in the back-side insulator and the isolation layer and is between the line-shaped opening and the front contact plug; and
forming a back-side conductive layer in the back-side opening and the line-shaped opening, thereby forming the back contact plug in the back-side opening and forming the back-side power rail in the line-shaped opening.
8 . The method of claim 1 , further comprising, after forming the front contact plug and before forming the back-side insulator, removing a lower portion of the substrate until the lower surface of the isolation layer is exposed.
9 . The method of claim 1 , wherein the portions of the first and second sacrificial stack structures are first portions, and the first and second sacrificial stack structures each further comprise a second portion, and
the method further comprises forming a gate structure crossing over the first and second active regions and the etch stop layer, wherein forming the gate structure comprises replacing the sacrificial layers of the second portions of the first and second sacrificial stack structures with portions of the gate structure.
10 . The method of claim 1 , wherein an uppermost end of the etch stop layer is not farther than the upper surfaces of the first and second active regions from the substrate.
11 . The method of claim 1 , wherein both the portion of the front contact plug and the portion of the back contact plug are in the etch stop layer.
12 . The method of claim 1 , wherein a width of the back contact plug increases with increasing distance from the front contact plug.
13 . A method of forming an integrated circuit device, the method comprising:
providing a substrate on which a front structure is provided, wherein the substrate comprises a front surface and a back surface opposite the front surface, and wherein the front structure comprises first and second active regions protruding from the front surface of the substrate, an isolation layer between the first and second active regions, an etch stop layer on the isolation layer, first and second channel layers respectively on the first and second active regions, first and second source/drain regions respectively on the first and second active regions and respectively contacting the first and second channel layers, and a gate structure crossing over the first and second channel layers and the isolation layer; and
forming a front contact that contacts the first source/drain region;
forming a back-side insulator after forming the front contact, wherein the isolation layer is between the etch stop layer and the back-side insulator; and
forming a back contact plug that is in the isolation layer and the back-side insulator and contacts the front contact.
14 . The method of claim 13 , wherein forming the back contact plug comprises:
etching the back-side insulator and the isolation layer, thereby forming a back-side opening in the back-side insulator and the isolation layer; and
forming the back contact plug in the back-side opening.
15 . The method of claim 13 , wherein at least one of a portion of the front contact and a portion of the back contact plug is in the etch stop layer.
16 . The method of claim 15 , wherein the etch stop layer comprises a portion between the gate structure and the isolation layer.