Self-aligned laterally extended strap for a dynamic random access memory cell
A self-aligned strap structure can be formed by forming trench capacitors and overlying trench top conductive material portions. End portions of fin mask structures overlie portions of the trench top conductive material portions. A dielectric spacer is formed around each end portions of the fin mask structure to cover additional areas of the trench top conductive material portions. An anisotropic etch is performed to recess portions of the trench top conductive material portions that are not covered by the fin mask structures or dielectric spacers. Conductive strap structures that are self-aligned to end portions of semiconductor fins are formed simultaneously with formation of the semiconductor fins. Access fin field effect transistors can be subsequently formed.
1. A semiconductor structure comprising:
a semiconductor fin located on a substrate and including a region having a first width and an end portion having a second width that is greater than said first width;
a trench capacitor located within said substrate and including an inner electrode, a node dielectric, and an outer electrode; and
a conductive strap structure, wherein a lower portion of said conductive strap structure vertically contacts said inner electrode and an upper portion of said conductive strap structure laterally contacts said semiconductor fin and includes a portion having said second width,
wherein a top surface of said semiconductor fin is coplanar with a top surface of said conductive strap structure.
2. The semiconductor structure of claim 1 , wherein a sidewall of said semiconductor fin and a sidewall of said conductive strap structure are within a same vertical plane.
3. The semiconductor structure of claim 1 , wherein a concave vertical sidewall of said semiconductor fin contacts a convex vertical sidewall of said conductive strap structure at an interface between said semiconductor fin and said conductive strap structure.
4. The semiconductor structure of claim 3 , wherein said convex vertical sidewall of said conductive strap structure is vertically coincident with an interface between said node dielectric and said outer electrode.
5. The semiconductor structure of claim 1 , wherein an entirety of sidewall surfaces of said conductive strap structure is vertically coincident with an interface between said node dielectric and said outer electrode.
6. The semiconductor structure of claim 1 , wherein an entirety of said upper portion of said conductive strap structure has a first horizontal cross-sectional shape including a pair of sidewalls laterally spaced by said second width, an entirety of said lower portion of said conductive strap structure has a second horizontal cross-sectional shape that is the same as a horizontal-cross-sectional shape of a trench embedding said node dielectric and said inner electrode.
7. The semiconductor structure of claim 1 , wherein outer surfaces of said conductive strap structure comprise a pair of convex vertical sidewalls that are adjoined to each other by a planar vertical sidewall that is perpendicular to a lengthwise direction of said semiconductor fin.
8. The semiconductor structure of claim 1 , further comprising an insulator layer contacting a bottom surface of said semiconductor fin and laterally surrounding said conductive strap structure and contacting outer surfaces of said node dielectric.
9. The semiconductor structure of claim 8 , wherein an interface between said conductive strap structure and said semiconductor fin is vertically coincident with an interface between said insulator layer and said conductive strap structure.
10. A semiconductor structure comprising:
a semiconductor fin located on a substrate and including a region having a first width and an end portion having a second width that is greater than said first width;
a trench capacitor located within said substrate and including an inner electrode, a node dielectric, and an outer electrode; and
a conductive strap structure, wherein a lower portion of said conductive strap structure vertically contacts said inner electrode and an upper portion of said conductive strap structure laterally contacts said semiconductor fin and includes a portion having said second width,
wherein an entirety of sidewall surfaces of said conductive strap structure is vertically coincident with an interface between said node dielectric and said outer electrode.
11. The semiconductor structure of claim 10 , wherein a sidewall of said semiconductor fin and a sidewall of said conductive strap structure are within a same vertical plane.
12. The semiconductor structure of claim 10 , wherein a concave vertical sidewall of said semiconductor fin contacts a convex vertical sidewall of said conductive strap structure at an interface between said semiconductor fin and said conductive strap structure.
13. The semiconductor structure of claim 12 , wherein said convex vertical sidewall of said conductive strap structure is vertically coincident with an interface between said node dielectric and said outer electrode.
14. The semiconductor structure of claim 10 , wherein an entirety of said upper portion of said conductive strap structure has a first horizontal cross-sectional shape including a pair of sidewalls laterally spaced by said second width, an entirety of said lower portion of said conductive strap structure has a second horizontal cross-sectional shape that is the same as a horizontal-cross-sectional shape of a trench embedding said node dielectric and said inner electrode.
15. The semiconductor structure of claim 10 , wherein a top surface of said semiconductor fin is coplanar with a top surface of said conductive strap structure.
16. The semiconductor structure of claim 10 , wherein outer surfaces of said conductive strap structure comprise a pair of convex vertical sidewalls that are adjoined to each other by a planar vertical sidewall that is perpendicular to a lengthwise direction of said semiconductor fin.
17. The semiconductor structure of claim 10 , further comprising an insulator layer contacting a bottom surface of said semiconductor fin and laterally surrounding said conductive strap structure and contacting outer surfaces of said node dielectric.
18. The semiconductor structure of claim 17 , wherein an interface between said conductive strap structure and said semiconductor fm is vertically coincident with an interface between said insulator layer and said conductive strap structure.
19. A semiconductor structure comprising:
a semiconductor fin located on a substrate and including a region having a first width and an end portion having a second width that is greater than said first width;
a trench capacitor located within said substrate and including an inner electrode, a node dielectric, and an outer electrode; and
a conductive strap structure, wherein a lower portion of said conductive strap structure vertically contacts said inner electrode and an upper portion of said conductive strap structure laterally contacts said semiconductor fin and includes a portion having said second width,
wherein an entirety of said upper portion of said conductive strap structure has a first horizontal cross-sectional shape including a pair of sidewalls laterally spaced by said second width, an entirety of said lower portion of said conductive strap structure has a second horizontal cross-sectional shape that is the same as a horizontal-cross-sectional shape of a trench embedding said node dielectric and said inner electrode.