Three-dimensional cross-point memory device containing inter-level connection structures and method of making the same
First electrically conductive lines, first pillar structures, second electrically conductive lines, second pillar structures, third electrically conductive lines, third pillar structures, fourth electrically conductive lines, and fourth pillar structures are formed over a substrate. Each pillar structure includes a memory element. Interconnection structures are formed on the first electrically conductive lines. The first electrically conductive lines may have thinned segments located outside the area of the arrays of memory elements, and the interconnection structures may be formed on the thinned segments. Alternatively or additionally, the interconnection structures may include a vertical stack of a first conductive via structure contacting a respective one of the first electrically conductive lines, a conductive pad structure, and a second conductive via structure. Fifth electrically conductive lines may be formed on top surfaces of the second two-dimensional array of memory elements and on top surface of the interconnection structures.
1. A memory device, comprising:
a vertical stack including first electrically conductive lines, a two-dimensional array of first pillar structures, second electrically conductive lines, a two-dimensional array of second pillar structures, third electrically conductive lines, a two-dimensional array of third pillar structures, fourth electrically conductive lines, a two-dimensional array of fourth pillar structures, and fifth electrically conductive lines, wherein each of the first pillar structures, the second pillar structures, the third pillar structures, and the fourth pillar structures comprises a respective memory element; and
interconnection structures providing electrically conductive paths between the fifth electrically conductive lines and the first electrically conductive lines, wherein each of the interconnection structures comprises a vertical stack of a first conductive via structure contacting a respective one of the first electrically conductive lines, a conductive pad structure contacting a top surface of the first conductive via structure, and a second conductive via structure contacting the conductive pad structure and a respective one of the fifth electrically conductive lines,
wherein:
the first electrically conductive lines, the third electrically conductive lines, and the fifth electrically conductive lines laterally extend along the first horizontal direction;
the second electrically conductive lines and the fourth electrically conductive lines laterally extend along a second horizontal direction;
the first electrically conductive lines have a first pitch along the second horizontal direction that is perpendicular to the first horizontal direction;
the conductive pad structures have a second pitch along the second horizontal direction;
the second pitch is the first pitch times an integer N that is greater than 1; and
each of the conductive pad structures has a pad width along the second horizontal direction, wherein the pad width is greater than the first pitch.
2. The memory device of claim 1 , wherein:
top surfaces of the conductive pad structures are located within a horizontal plane including the top surfaces of the third electrically conductive lines; and
bottom surfaces of the conducive pad structures are located within a horizontal plane including bottom surfaces of the third electrically conductive lines.
3. The memory device of claim 1 , wherein:
the two-dimensional array of first pillar structures is formed in a first dielectric material layer that laterally surrounds a lower portion of each of the first conductive via structures; and
the two-dimensional array of second pillar structures is formed in a second dielectric material layer that laterally surrounds an upper portion of each of the first conductive via structures.
4. The memory device of claim 1 , wherein:
the two-dimensional array of first pillar structures comprises a first periodic rectangular two-dimensional array of first memory elements; and
the two-dimensional array of second pillar structures comprises a second periodic rectangular two-dimensional array of second memory elements having a same two-dimensional periodicity as the two-dimensional array of first pillar structures.
5. The memory device of claim 1 , wherein each first pillar structure within the two-dimensional array of first pillar structures and each second pillar structure within the two-dimensional array of second pillar structures have at least one vertical or tapered sidewall that vertically extends from a topmost surface thereof to a bottommost surface thereof.
6. The memory device of claim 5 , wherein each of the first pillar structures and the second pillar structures comprises a series connection of a memory material portion and a selector material portion.
7. The memory device of claim 6 , wherein:
the memory material portion includes a phase change material; and
the selector material portion includes an ovonic threshold switch material.