Boundary structure for embedded memory
An integrated circuits device includes a semiconductor substrate having a logic region and a memory region separated by an isolation region having an isolation structure of dielectric material. A memory device is formed on the memory region and includes a gate electrode over a gate dielectric. A dummy gate structure is formed on the isolation structure. The dummy gate structure has a dummy gate electrode layer corresponding to the gate electrode and a dummy gate dielectric layer corresponding to the gate dielectric. A tapered sidewall structure is formed on a logic region-facing side of the dummy gate structure. The tapered sidewall structure is spaced above the isolation structure and either adjacent to or contiguous with the dummy gate electrode layer.
1. An integrated circuit (IC) comprising:
a semiconductor substrate including a logic area and a memory area;
a shallow trench isolation structure on the semiconductor substrate between the logic area and the memory area, wherein the shallow trench isolation structure comprises a dielectric material;
a memory device on the memory area, wherein the memory device includes a gate electrode directly over a gate dielectric;
a dummy gate structure directly over the shallow trench isolation structure, the dummy gate structure comprising a dummy gate electrode layer directly over a dummy gate dielectric layer; and
a tapered sidewall structure on a side of the dummy gate structure that faces the logic area, wherein the tapered sidewall structure is directly and entirely over the shallow trench isolation structure, is spaced above the shallow trench isolation structure, and is either adjacent to or contiguous with the dummy gate electrode layer;
wherein the tapered sidewall structure is above the dummy gate dielectric layer;
the dummy gate electrode layer has a composition of the gate electrode; and
the dummy gate dielectric layer has a composition of the gate dielectric.
2. The IC of claim 1 , wherein the tapered sidewall structure is directly over the dummy gate electrode layer.
3. The IC of claim 1 , wherein:
the dummy gate dielectric layer has a thickness; and
the tapered sidewall structure is spaced above the shallow trench isolation structure by a distance less than or equal to the thickness of the dummy gate dielectric layer.
4. The IC of claim 1 , wherein:
the tapered sidewall structure tapers toward the logic area; and
the dummy gate dielectric layer is confined below the tapered sidewall structure.
5. An integrated circuit (IC) comprising:
a semiconductor substrate including a logic region and a memory region;
a memory device on the memory region, wherein the memory device includes a gate electrode directly over a gate dielectric;
a dummy gate structure and a shallow trench isolation structure between the logic region and the memory region and having a dummy gate electrode layer directly over a dummy gate dielectric layer; and
a tapered sidewall structure on a side of the dummy gate structure that faces the logic region, wherein the tapered sidewall structure is adjacent to the dummy gate electrode layer;
wherein the dummy gate electrode has a composition corresponding to the gate electrode;
the tapered sidewall structure is directly and entirely over the shallow trench isolation structure;
the dummy gate dielectric has a composition corresponding to the gate dielectric;
the tapered sidewall structure is formed of a conductive material; and
the tapered sidewall structure is separated from the dummy gate electrode layer by a native oxide formed on the dummy gate electrode layer.
6. The IC of claim 1 , wherein the tapered sidewall structure is formed by the dummy gate electrode layer.
7. The IC of claim 1 , wherein the dummy gate dielectric layer comprises a nitride layer between two oxide layers.
8. An integrated circuit (IC) comprising:
a semiconductor substrate including a logic region and a memory region;
an isolation structure between the logic region and the memory region;
a memory device on the memory region, wherein the memory device includes a gate electrode directly over a gate dielectric;
a dummy gate structure between the logic region and the memory region and having a dummy gate electrode layer directly over a dummy gate dielectric layer; and
a tapered sidewall structure on a side of the dummy gate structure that faces the logic region, wherein the tapered sidewall structure is either adjacent to or contiguous with the dummy gate electrode layer;
wherein the dummy gate electrode has a composition of the gate electrode;
the dummy gate dielectric has a composition of the gate dielectric;
one or more layers of the dummy gate dielectric layer are cut off short from extending fully beneath the tapered sidewall structure to create an area between the isolation structure and the tapered sidewall structure from which the dummy gate dielectric layer is absent; and
the area between the isolation structure and the tapered sidewall structure from which the dummy gate dielectric layer is absent is filled with a dielectric having a different composition or structure from the dummy gate dielectric layer.
9. The IC of claim 1 , wherein the side of the dummy gate structure that faces the logic area includes one or more dielectric layers that are above the dummy gate electrode layer and are recessed from the logic area relative to the dummy gate electrode layer.
10. The IC of claim 1 , wherein the tapered sidewall structure is polysilicon.
11. The IC of claim 1 , wherein the tapered sidewall structure is dielectric.
12. The IC of claim 1 , wherein the tapered sidewall structure comprises a lower layer that is polysilicon and an upper layer that is dielectric.
13. The IC of claim 1 , wherein the tapered sidewall structure is spaced above the isolation structure by a distance equal to a thickness of the dummy gate dielectric layer.
14. The IC of claim 1 , wherein the gate electrode is disposed over a floating gate.
15. The IC of claim 1 , wherein high K metal gates are disposed in the logic area.
16. The IC of claim 1 , wherein a dielectric distinct from the dummy gate dielectric layer is disposed adjacent the dummy gate dielectric layer and underneath the tapered sidewall structure.
17. The IC of claim 5 , wherein:
the dummy gate structure is directly above an isolation structure;
the dummy gate dielectric layer has a thickness; and
the tapered sidewall structure is spaced above the isolation structure by a distance less than or equal to the thickness of the dummy gate dielectric layer.
18. The IC of claim 5 , wherein:
the dummy gate structure is directly above an isolation structure;
the dummy gate dielectric layer has a thickness; and
the tapered sidewall structure is spaced above the isolation structure by a distance equal to the thickness of the dummy gate dielectric layer.
19. The IC of claim 8 , wherein:
the dummy gate structure is directly above an isolation structure;
the dummy gate dielectric layer has a thickness; and
the tapered sidewall structure is spaced above the isolation structure by a distance less than or equal to the thickness of the dummy gate dielectric layer.
20. The IC of claim 8 , wherein:
the dummy gate structure is directly above an isolation structure;
the dummy gate dielectric layer has a thickness; and
the tapered sidewall structure is spaced above the isolation structure by a distance equal to the thickness of the dummy gate dielectric layer.