Three-dimensional memory device containing eye-shaped contact via structures located in laterally-undulating trenches and method of making the same
A three-dimensional memory device includes alternating stacks of insulating layers and electrically conductive layers located over a semiconductor material layer, and memory stack structures extending through one of the alternating stacks. Laterally-undulating backside trenches are present between alternating stacks, and include a laterally alternating sequence of straight trench segments and bulging trench segments. Cavity-containing dielectric fill structures and contact via structures are present in the laterally-undulating backside trenches. The contact via structures are located within the bulging trench segments. The contact via structures are self-aligned to sidewalls of the alternating stacks. Additional contact via structures may vertically extend through a dielectric alternating stack of a subset of the insulating layers and dielectric spacer layers laterally adjoining one of the alternating stacks.
1. A three-dimensional memory device, comprising:
alternating stacks of insulating layers and electrically conductive layers located over a semiconductor material layer;
memory stack structures extending through a first alternating stack selected from the alternating stacks of insulating layers and electrically conductive layers;
laterally-undulating backside trenches located between neighboring pairs of the alternating stacks of insulating layers and electrically conductive layers and laterally extending along a first horizontal direction;
cavity-containing dielectric fill structures located within a respective one of the laterally-undulating backside trenches;
first contact via structures located within vertically-extending cavities of the cavity-containing dielectric fill structures located within a respective one of the laterally-undulating backside trenches and extending to the semiconductor material layer;
a dielectric alternating stack of insulating layers and dielectric spacer layers laterally adjoining one of the alternating stacks of insulating layers and electrically conductive layers such that insulating layers of the dielectric alternating stack are continuous with insulating layers of the laterally adjoining one of the alternating stacks of insulating layers and electrically conductive layers; and
laterally-insulated second contact via structures extending through the dielectric alternating stack, wherein each of the laterally-insulated second contact via structures is surrounded by a respective tubular dielectric spacer.
2. The three-dimensional memory device of claim 1 , wherein each of the laterally-undulating backside trenches comprises a laterally alternating sequence of straight trench segments having a uniform trench width and bulging trench segments having a variable trench width that is greater than the uniform trench width.
3. The three-dimensional memory device of claim 1 , wherein a topmost portion of each of the cavity-containing dielectric fill structures that contact the first contact via structures has a same lateral thickness as a topmost portion of each of the tubular dielectric spacers.
4. The three-dimensional memory device of claim 3 , wherein each of the tubular dielectric spacers is laterally spaced from the dielectric alternating stack by a dielectric liner having a different material composition than the dielectric spacer layers.
5. The three-dimensional memory device of claim 4 , wherein:
the dielectric liners comprise a semiconductor oxide material and contacts a respective upper portion of the semiconductor material layer; and
the tubular dielectric spacers contact a respective lower portion of the semiconductor material layer.
6. The three-dimensional memory device of claim 3 , wherein each of the electrically conductive layers is located between a respective first horizontal plane including a top surface of a respective one of the dielectric spacer layers and a respective second horizontal plane including a bottom surface of the respective one of the dielectric spacer layers.
7. The three-dimensional memory device of claim 6 , wherein:
the insulating layers comprise doped silicate glass, undoped silicate glass, or organosilicate glass;
the dielectric spacer layers comprise silicon nitride; and
the second contact via structures comprise at least one metallic material.
8. The three-dimensional memory device of claim 1 , further comprising:
field effect transistors located on a substrate that underlies the semiconductor material layer; and
lower-level metal interconnect structures formed in lower-level dielectric material layers that overlie the field effect transistors and electrically connected to nodes of the field effect transistors, wherein the first contact via structures and the second contact via structures extend through the semiconductor material layer and contact a top surface of a respective one of the lower-level metal interconnect structures.
9. The three-dimensional memory device of claim 1 , wherein:
the semiconductor material layer comprises a source semiconductor layer including a doped semiconductor material and is laterally spaced from the first contact via structures by the cavity-containing dielectric fill structures;
a lower portion of the source semiconductor layer contacts outer sidewalls of the cavity-containing dielectric fill structures; and
an upper portion of the source semiconductor layer is laterally spaced from the outer sidewalls of the cavity-containing dielectric fill structures by semiconductor oxide portions.
10. The three-dimensional memory device of claim 1 , wherein:
each of the memory stack structures comprises a respective vertical semiconductor channel and a respective memory film; and
the semiconductor material layer comprises a source semiconductor layer including a doped semiconductor material and is electrically connected to bottom ends of the vertical semiconductor channels.
11. The three-dimensional memory device of claim 1 , wherein:
the cavity-containing dielectric fill structures and the tubular dielectric spacers comprise a same dielectric material; and
the first contact via structures and the second contact via structures comprise a same set of at least one metallic material.
12. The three-dimensional memory device of claim 1 , wherein:
a subset of the first contact via structures is located within a contact tab region in which second alternating stacks selected from the alternating stacks of insulating layers and electrically conductive layers are present, wherein the contact tab region is free of any memory stack structure; and
support pillar structures vertically extend through each of the second alternating stacks.
13. The three-dimensional memory device of claim 12 , wherein:
each of the support pillar structures consists of at least one dielectric material or is electrically inactive; and
the contact tab region is laterally spaced from a memory array region including the first alternating stack by a straight trench that extends along the first horizontal direction with a uniform width throughout.
14. The three-dimensional memory device of claim 1 , wherein each lengthwise sidewall of the laterally-undulating backside trenches that laterally extend along the first horizontal direction comprises a respective laterally alternating sequences of bulging trench segments that are parallel to the first horizontal direction and concave semi-cylindrical sidewall segments that laterally protrude into a respective one of the alternating stacks of insulating layers and electrically conductive layers.