Anti-dishing structure for embedded memory
Some embodiments of the present application are directed towards an integrated circuit (IC). The integrated circuit includes a semiconductor substrate including a logic region and a memory cell region. A logic device is arranged on the logic region. A memory device is arranged on the memory cell region. An isolation structure extends into a top surface of the semiconductor substrate, and laterally separates the logic region from the memory cell region. The isolation structure includes dielectric material and has an uppermost surface and a slanted upper surface extending from the uppermost surface to an edge of the isolation structure proximate to memory cell region.
1 . An integrated circuit (IC), comprising:
a semiconductor substrate including a memory region and a logic region;
an isolation structure disposed in the semiconductor substrate and separating the memory region from the logic region; and
an array of split gate flash memory cell structures disposed on the memory region, the array of split gate flash memory cell structures comprising a central memory cell in a central region of the array and an edge memory cell in an edge region of the array, the edge region spaced between the central region and the isolation structure; wherein the edge memory cell includes an edge gate electrode and an edge gate electrode hardmask over the edge gate electrode, and the central memory cell includes a central gate electrode and a central gate electrode hardmask over the central gate electrode;
wherein the isolation structure has an uppermost surface, a slanted upper surface extending from the uppermost surface of the isolation structure to an edge of the isolation structure proximate to the memory region, and a slanted sidewall extending up from a top surface of the semiconductor substrate to the edge of the slanted upper surface, wherein an acute angle is defined at an inner corner between a first tangent line for the uppermost surface of the isolation structure and a second tangent line for the slanted sidewall of the isolation structure; a dummy control gate structure disposed on the isolation structure, wherein the dummy control gate structure has an inner sidewall facing the memory region; and a sidewall spacer along the inner sidewall of the dummy control gate structure and disposed on the isolation structure, wherein the sidewall spacer has an inner sidewall facing the memory region.
2 . The IC of claim 1 , further comprising:
a logic device on the logic region, wherein the logic device includes a conductive logic gate electrode;
wherein an upper surface of the edge gate electrode and an upper surface of the conductive logic gate electrode have equal heights as measured from the top surface of the semiconductor substrate.
3 . The IC of claim 2 , wherein the upper surface of the conductive logic gate electrode and the upper surface of the central gate electrode hardmask have a difference in height ranging between approximately 40 angstroms and approximately 10 angstroms.
4 . The IC of claim 1 , wherein the edge gate electrode is a select gate electrode of a flash memory cell.
5 . The IC of claim 1 , wherein the central gate electrode is a select gate electrode of a flash memory cell.
6 . The IC of claim 1 , wherein the edge gate electrode and the central gate electrode are each a select gate electrode.
7 . The IC according to claim 1 , wherein the sidewall spacer comprises: an outer oxide layer along the inner sidewall of the dummy control gate structure; a nitride layer along an inner sidewall of the outer oxide layer; and an inner oxide layer along an inner sidewall of the nitride layer, the inner oxide layer having an inner sidewall that contacts an outer sidewall of a dummy select gate structure.
8 . The IC according to claim 1 , wherein at least one of the edge memory cell and/or the central memory cell comprises: first and second individual source/drain regions in the semiconductor substrate; a common source/drain region in the semiconductor substrate, laterally spaced between the first and second individual source/drain regions, wherein the common source/drain region is separated from the first individual source/drain region by a first channel region, and wherein the common source/drain region is separated from the second individual source/drain region by a second channel region; an erase gate electrode over the common source/drain region; first and second floating gate electrodes respectively over the first and second channel regions; first and second control gate electrodes respectively overlying the first and second floating gate electrodes; and a first select gate electrode and a second select gate electrode respectively over the first and second channel regions, and laterally spaced from the common source/drain region respectively by the first and second floating gate electrodes.
9 . An integrated circuit, comprising:
a semiconductor substrate including a logic region and a memory cell region;
an isolation structure extending into a top surface of the semiconductor substrate and separating the logic region from the memory cell region, the isolation structure comprising dielectric material and having an uppermost surface, a slanted upper surface extending from the uppermost surface to an edge of the isolation structure proximate to memory cell region, and a slanted sidewall extending up from the top surface of the semiconductor substrate to an edge of the slanted upper surface,
wherein an acute angle is defined at an intersection of a first tangent line for the uppermost surface of the isolation structure and a second tangent line for the slanted sidewall of the isolation structure;
a logic device disposed on the logic region;
a memory device disposed on the memory cell region, wherein the memory device includes a first select gate electrode;
a dummy select gate structure made of conductive material disposed on the isolation structure, wherein an upper surface of the dummy select gate structure and an upper surface of the first select gate electrode have equal heights as measured from the top surface of the semiconductor substrate;
a dielectric layer over the isolation structure, the dielectric layer comprising an uppermost surface and a recessed upper surface, the uppermost surface being level with the upper surface of the first select gate electrode and the recessed upper surface being below the uppermost surface; and
an inter-layer dielectric (ILD) layer disposed over the recessed upper surface and having an upper surface that is level with the uppermost surface of the dielectric layer.
10 . The integrated circuit of claim 9 , wherein the dielectric layer extends continuously along a sidewall of the isolation structure and over an upper surface of the isolation structure.
11 . The integrated circuit of claim 9 , wherein the dielectric layer extends continuously over an upper surface of the isolation structure and along a sidewall of the dummy select gate structure.
12 . The integrated circuit of claim 9 , further comprising:
a dummy control gate structure disposed on the isolation structure, wherein the dummy control gate structure has an inner sidewall facing the memory cell region; and
a sidewall spacer along the inner sidewall of the dummy control gate structure and disposed on the isolation structure, wherein the sidewall spacer has an inner sidewall facing the memory cell region; and
wherein the dummy select gate structure is disposed along the inner sidewall of the sidewall spacer and disposed on the isolation structure.
13 . The integrated circuit of claim 9 , wherein the memory device includes an array of split gate flash memory cell structures disposed on the memory cell region.
14 . An integrated circuit (IC), comprising:
a semiconductor substrate including a logic region and a memory cell region;
a logic device on the logic region; a memory device on the memory cell region; and an isolation structure extending into a top surface of the semiconductor substrate and laterally separating the logic region from the memory cell region, the isolation structure comprising dielectric material and having an uppermost surface, and a slanted upper surface extending from the uppermost surface to an edge of the isolation structure proximate to the memory cell region, and a slanted sidewall extending up from the top surface of the semiconductor substrate to an edge of the slanted upper surface, wherein an acute angle is defined at an inner corner between intersection of a first tangent line for the uppermost surface of the isolation structure and a second tangent line for the slanted upper surface sidewall of the isolation structure; a dummy gate structure made of conductive material disposed on the uppermost surface of the isolation structure, wherein an upper surface of the dummy gate structure and an upper surface of a gate electrode of the memory device have equal heights as measured from the top surface of the semiconductor substrate.
15 . The IC of claim 14 , wherein the uppermost surface of the isolation structure is a lateral surface.
16 . The IC of claim 14 , further comprising:
a dielectric layer over the isolation structure, wherein the dielectric layer extends continuously along a sidewall of the isolation structure and over the uppermost surface of the isolation structure.
17 . The IC of claim 14 , wherein the memory device comprises an array of split gate flash memory cell structures disposed on the memory cell region, the array of split gate flash memory cell structures comprising a central memory cell in a central region of the array and an edge memory cell in an edge region of the array, the edge region spaced between the central region and the isolation structure; wherein the edge memory cell includes an edge gate electrode and an edge gate electrode hardmask over the edge gate electrode, and the central memory cell includes a central gate electrode and a central gate electrode hardmask over the central gate electrode;
wherein there is a difference in height between an upper surface of the edge gate electrode hardmask and an upper surface of the central gate electrode hardmask, the difference in height ranging between approximately 40 angstroms and approximately 10 angstroms.
18 . The IC of claim 14 , further comprising:
a dummy gate structure disposed on the isolation structure; and
a sidewall spacer along a sidewall of the dummy gate structure and disposed on the isolation structure.