MIM capacitor structure
The present disclosure relates to a MIM capacitor, and an associated method of formation. In some embodiments, the MIM capacitor has a first electrode having a bottom capacitor metal layer disposed over a semiconductor substrate. A second electrode having a middle capacitor metal layer overlies the bottom capacitor metal layer. A third electrode having a top capacitor metal layer has a stepped structure is laterally and vertically separated from the middle capacitor metal layer by a capacitor dielectric layer continuously extends from a first position between the bottom capacitor metal layer and the middle capacitor metal layer, to a second position between the middle capacitor metal layer and the top capacitor metal layer. The capacitor dielectric layer allows for the MIM capacitor to have a structure that improves fabrication of the capacitor.
1. A MIM (metal-insulator-metal) capacitor, comprising:
a first electrode comprising a bottom capacitor metal layer disposed over a semiconductor substrate;
a second electrode comprising a middle capacitor metal layer overlying the bottom capacitor metal layer; and
a third electrode comprising a top capacitor metal layer comprising a stepped structure that is vertically and laterally separated from the middle capacitor metal layer by a capacitor dielectric layer that continuously extends from a first position between the bottom capacitor metal layer and the middle capacitor metal layer, to a second position between the middle capacitor metal layer and the top capacitor metal layer.
2. The MIM capacitor of claim 1 , further comprising:
a dielectric buffer layer disposed below the bottom capacitor metal layer; and
an under-metal layer separated from the bottom capacitor metal layer by the dielectric buffer layer, wherein the under-metal layer comprises one or more metal structures located under the bottom capacitor metal layer.
3. The MIM capacitor of claim 2 ,
wherein the capacitor dielectric layer may branches out from a main branch abutting the dielectric buffer layer to a lower branch and an upper branch; and
wherein the lower branch is disposed between the bottom capacitor metal layer and the middle capacitor metal layer, and wherein the upper branch is disposed between the middle capacitor metal layer and the top capacitor metal layer.
4. The MIM capacitor of claim 1 , wherein the capacitor dielectric layer has a thickness that varies from a first thickness between the bottom capacitor metal layer and the top capacitor metal layer to a second thickness between the bottom capacitor metal layer and the middle capacitor metal layer, and to a third thickness between the middle capacitor metal layer and the top capacitor metal layer.
5. The MIM capacitor of claim 1 , further comprising:
a capacitor inter-level dielectric (ILD) layer disposed over the top capacitor metal layer; and
a substantially planar second etch stop layer disposed over the capacitor ILD layer.
6. The MIM capacitor of claim 5 , further comprising:
a first via vertically extending through the capacitor ILD layer to a first position that electrically contacts the bottom capacitor metal layer;
a second via vertically extending through the capacitor ILD layer to a second position that electrically contacts the middle capacitor metal layer; and
a third via vertically extending through the capacitor ILD layer to a third position that electrically contacts the top capacitor metal layer.
7. The MIM capacitor of claim 1 , wherein the bottom capacitor metal layer, the middle capacitor metal layer, and the top capacitor metal layer have a thickness that is between approximately 100 angstrom and approximately 800 angstrom.
8. The MIM capacitor of claim 1 , further comprising:
a capacitor etch stop layer extending laterally from over the top capacitor metal layer over the bottom capacitor metal layer.
9. The MIM capacitor of claim 8 , further comprising a cap layer having a first side abutting the top capacitor metal layer and the dielectric layer, and having an opposing second side abutting the capacitor etch stop layer.
10. A method of forming a MIM capacitor, comprising:
forming a first electrode comprising a bottom capacitor metal layer;
forming a capacitor dielectric layer over the bottom capacitor metal layer;
forming a second electrode comprising a middle capacitor metal layer separated from the bottom capacitor metal layer by the capacitor dielectric layer;
modifying the capacitor dielectric layer to extend over the middle capacitor metal layer; and
forming a third electrode comprising a top capacitor metal layer comprising a stepped structure that is vertically and laterally separated from the middle capacitor metal layer by the capacitor dielectric layer.
11. A MIM capacitor, comprising:
a bottom capacitor metal layer disposed over a semiconductor substrate;
a middle capacitor metal layer overlying the bottom capacitor metal layer;
a top capacitor metal layer overlying the middle capacitor metal layer;
a capacitor dielectric layer having a first lateral segment vertically arranged between the bottom capacitor metal layer and the middle capacitor metal layer, a second lateral segment vertically arranged between the middle capacitor metal layer and the top capacitor metal layer, and a vertical segment connected to the first lateral segment and the second lateral segment and laterally arranged between the middle capacitor metal layer and the top capacitor metal layer; and
a capacitor inter-level dielectric (ILD) layer overlying the bottom capacitor metal layer, the middle capacitor metal layer, and the top capacitor metal layer.
12. The MIM capacitor of claim 11 , wherein the top capacitor metal layer has a first sidewall that is laterally set back from a sidewall of the middle capacitor metal layer.
13. The MIM capacitor of claim 11 , wherein the top capacitor metal layer has a second sidewall that is laterally aligned with a sidewall of the capacitor dielectric layer.
14. The MIM capacitor of claim 11 , wherein the top capacitor metal layer comprises a stepped structure that is vertically and laterally separated from the middle capacitor metal layer by the capacitor dielectric layer.
15. The MIM capacitor of claim 11 , further comprising:
a substantially planar etch stop layer vertically arranged between the capacitor ILD layer and a metal ILD layer overlying the capacitor ILD layer.
16. The MIM capacitor of claim 11 , wherein the bottom capacitor metal layer is vertically separated from an underlying metal layer by a dielectric buffer layer.
17. The MIM capacitor of claim 16 , wherein the dielectric buffer layer and the capacitor ILD layer are a same material.
18. The MIM capacitor of claim 11 , further comprising:
a plurality of conductive vias vertically extending from an upper surface of the capacitor ILD layer to the bottom capacitor metal layer, the middle capacitor metal layer, and the top capacitor metal layer.
19. The MIM capacitor of claim 11 , further comprising:
a cap layer in direct contact with an upper surface of the top capacitor metal layer and a sidewall of middle capacitor metal layer.
20. The MIM capacitor of claim 19 , wherein the cap layer is in direct contact with the upper surface of the top capacitor metal layer and the second lateral segment of the capacitor dielectric layer.