FinFET split gate non-volatile memory cells with enhanced floating gate to floating gate capacitive coupling
Memory cells formed on upwardly extending fins of a semiconductor substrate, each including source and drain regions with a channel region therebetween, a floating gate extending along the channel region and wrapping around the fin, a word line gate extending along the channel region and wrapping around the fin, a control gate over the floating gate, and an erase gate over the source region. The control gates are a continuous conductive strip of material. First and second fins are spaced apart by a first distance. Third and fourth fins are spaced apart by a second distance. The second and third fins are spaced apart by a third distance greater than the first and second distances. The continuous strip includes a portion disposed between the second and third fins, but no portion of the continuous strip is disposed between the first and second fins nor between the third and fourth fins.
1. A memory device, comprising:
a semiconductor substrate having an upper surface with a plurality of fins that extend upwardly, wherein each of the fins includes opposing side surfaces that terminate in a top surface;
each of the plurality of fins includes a memory cell formed thereon that includes:
spaced apart source and drain regions in the fin, with a channel region of the fin extending along the opposing side surfaces and top surface of the fin between the source and drain regions,
a floating gate that extends along a first portion of the channel region, wherein the floating gate wraps around the fin such that the floating gate extends along and is insulated from the opposing side surfaces and the top surface of the fin,
a word line gate that extends along a second portion of the channel region, wherein the word line gate wraps around the fin such that the word line gate extends along and is insulated from the opposing side surfaces and the top surface of the fin,
a control gate that is disposed over and insulated from the floating gate, and
an erase gate that is disposed over and insulated from the source region;
wherein:
the control gates are a first continuous strip of conductive material;
first, second, third and fourth fins of the plurality of fins each have lengths that are parallel to a first direction;
the first and second fins are adjacent to each other, and spaced apart by a first distance;
the third and fourth fins are adjacent to each other, and spaced apart by a second distance;
the second and third fins are adjacent to each other, and spaced apart by a third distance; and
the first continuous strip of conductive material includes a portion that is disposed between the second and third fins, but no portion of the first continuous strip of conductive material is disposed between the first and second fins, and no portion of the first continuous strip of conductive material is disposed between the third and fourth fins.
2. The memory device of claim 1 , wherein the portion of the first continuous strip of conductive material disposed between the second and third fins is disposed between the floating gate wrapped around the second fin and the floating gate wrapped around the third fin.
3. The memory device of claim 2 , wherein no portion of the first continuous strip of conductive material is disposed between the floating gate wrapped around the first fin and the floating gate wrapped around the second fin, and wherein no portion of the first continuous strip of conductive material is disposed between the floating gate wrapped around the third fin and the floating gate wrapped around the fourth fin.
4. The memory device of claim 1 , wherein the third distance is greater than the first and second distances.
5. The memory device of claim 4 , wherein the first and second distances are equal to each other.
6. The memory device of claim 1 , wherein each of the erase gates wraps around one of the fins such that the erase gate extends along and is insulated from the opposing side surfaces and the top surface of the one fin.
7. The memory device of claim 1 , further comprising:
a plurality of logic fins of the semiconductor substrate upper surface that extend upwardly, wherein each of the logic fins includes opposing side surfaces that terminate in a top surface; and
each of the plurality of logic fins includes a logic device formed thereon that includes:
spaced apart logic source and logic drain regions in the logic fin, with a logic channel region of the logic fin extending along the opposing side surfaces and top surface of the logic fin between the logic source and logic drain regions, and
a logic gate that extends along the logic channel region, wherein the logic gate wraps around the logic fin such that the logic gate extends along and is insulated from the opposing side surfaces and the top surface of the logic fin.
8. The memory device of claim 7 , wherein the logic gates are a second continuous strip of conductive material.
9. The memory device of claim 1 , further comprising:
a source fin of the semiconductor substrate upper surface that extends upwardly, wherein:
the source fin includes opposing side surfaces that terminate in a top surface,
the source fin has a length that is parallel to a second direction orthogonal to the first direction,
the source fin intersects the first, second, third and fourth fins, and
each of the source regions is formed at an intersection of the source fin and one of the first, second, third and fourth fins.
10. A method of forming a memory device, comprising:
forming a plurality of fins that extend upwardly from an upper surface of a semiconductor substrate, wherein each of the fins includes opposing side surfaces that terminate in a top surface; and
forming a memory cell on each one of the plurality of fins, wherein the forming of each of the memory cells on one of the fins includes:
forming spaced apart source and drain regions in the fin, with a channel region of the fin extending along the opposing side surfaces and top surface of the fin between the source and drain regions,
forming a floating gate that extends along a first portion of the channel region, wherein the floating gate wraps around the fin such that the floating gate extends along and is insulated from the opposing side surfaces and the top surface of the fin,
forming a word line gate that extends along a second portion of the channel region, wherein the word line gate wraps around the fin such that the word line gate extends along and is insulated from the opposing side surfaces and the top surface of the fin,
forming a control gate that is disposed over and insulated from the floating gate, and
forming an erase gate that is disposed over and insulated from the source region;
wherein:
the control gates are a first continuous strip of conductive material;
first, second, third and fourth fins of the plurality of fins each have lengths that are parallel to a first direction;
the first and second fins are adjacent to each other, and spaced apart by a first distance;
the third and fourth fins are adjacent to each other, and spaced apart by a second distance;
the second and third fins are adjacent to each other, and spaced apart by a third distance; and
the first continuous strip of conductive material includes a portion that is disposed between the second and third fins, but no portion of the first continuous strip of conductive material is disposed between the first and second fins, and no portion of the first continuous strip of conductive material is disposed between the third and fourth fins.
11. The method of claim 10 , wherein the portion of the first continuous strip of conductive material disposed between the second and third fins is disposed between the floating gate wrapped around the second fin and the floating gate wrapped around the third fin.
12. The method of claim 11 , wherein no portion of the first continuous strip of conductive material is disposed between the floating gate wrapped around the first fin and the floating gate wrapped around the second fin, and wherein no portion of the first continuous strip of conductive material is disposed between the floating gate wrapped around the third fin and the floating gate wrapped around the fourth fin.
13. The method of claim 10 , wherein the third distance is greater than the first and second distances.
14. The method of claim 13 , wherein the first and second distances are equal to each other.
15. The method of claim 10 , wherein each of the erase gates wraps around one of the fins such that the erase gate extends along and is insulated from the opposing side surfaces and the top surface of the one fin.
16. The method of claim 10 , further comprising:
forming a plurality of logic fins of the semiconductor substrate upper surface that extend upwardly, wherein each of the logic fins includes opposing side surfaces that terminate in a top surface; and
forming a logic device on each one of the plurality of logic fins, wherein the forming of each of the logic devices on one of the logic fins includes:
forming spaced apart logic source and logic drain regions in the logic fin, with a logic channel region of the logic fin extending along the opposing side surfaces and top surface of the logic fin between the logic source and logic drain regions, and
forming a logic gate that extends along the logic channel region, wherein the logic gate wraps around the logic fin such that the logic gate extends along and is insulated from the opposing side surfaces and the top surface of the logic fin.
17. The method of claim 16 , wherein the logic gates are a second continuous strip of conductive material.
18. The method of claim 10 , further comprising:
forming a source fin of the semiconductor substrate upper surface that extends upwardly, wherein:
the source fin includes opposing side surfaces that terminate in a top surface,
the source fin has a length that is parallel to a second direction orthogonal to the first direction,
the source fin intersects the first, second, third and fourth fins, and
each of the source regions is formed at an intersection of the source fin and one of the first, second, third and fourth fins.