Through-stack contact via structures for a three-dimensional memory device and methods of forming the same
A first-tier structure includes a first vertically alternating sequence of first continuous insulating layers and first continuous sacrificial material layers and a first-tier retro-stepped dielectric material portion overlying first stepped surfaces of the first vertically alternating sequence. A second vertically alternating sequence of second continuous insulating layers and second continuous sacrificial material layers is formed over the first-tier structure. Retro-stepped dielectric material portions are formed in each of the first-tier structure and the second-tier structure. After formation of memory stack structures, electrically conductive layers replace portions of the first and second continuous sacrificial material layers. Laterally-isolated contact via structures can be formed through the second-tier structure and a first-tier retro-stepped dielectric material portion on first electrically conductive layers in the first-tier structure. Sacrificial landing pad structures can be employed to enable concurrent formation of contact via cavities through the retro-stepped dielectric material portions.
1. A three-dimensional memory device comprising:
a first-tier alternating stack of first insulating layers and first electrically conductive layers located over a substrate;
a first-tier retro-stepped dielectric material portion overlying first stepped surfaces of the first-tier alternating stack;
a second-tier alternating stack of second insulating layers and second electrically conductive layers that overlies the first-tier alternating stack and the first-tier retro-stepped dielectric material portion;
a second-tier retro-stepped dielectric material portion overlying second stepped surfaces of the second-tier alternating stack, wherein the second-tier retro-stepped dielectric material portion is laterally offset from the first-tier retro-stepped dielectric material portion;
first memory stack structures located in a first memory array region in which each layer of the first-tier alternating stack and each layer of the second-tier alternating stack are present, wherein each of the first memory stack structures comprises a respective memory film and a respective vertical semiconductor channel; and
laterally-isolated contact via structures vertically extending through the second-tier alternating stack and the first-tier retro-stepped dielectric material portion and contacting a respective one of the first electrically conductive layers, wherein each of the laterally-isolated contact via structures comprises a first contact via structure and a tubular insulating liner that surrounds the first contact via structure.
2. The three-dimensional memory device of claim 1 , wherein a bottom portion of each tubular insulating liner comprises a respective sidewall that contacts the first-tier retro-stepped dielectric material portion.
3. The three-dimensional memory device of claim 2 , wherein a tubular insulating liner of the tubular insulating liners comprises:
a cylindrical portion vertically extending through the second-tier alternating stack; and
a base portion located at a bottom of the cylindrical portion, underlying the second-tier alternating stack and embedded in and contacting the first-tier retro-stepped dielectric material portion.
4. The three-dimensional memory device of claim 3 , wherein the base portion comprises an annular top surface contacting a bottom surface of a bottommost layer within the second-tier alternating stack.
5. The three-dimensional memory device of claim 3 , wherein the base portion has an annular bottom surface that contacts a recessed horizontal surface of the first-tier retro-stepped dielectric material portion.
6. The three-dimensional memory device of claim 3 , wherein the base portion has a greater lateral dimension than a maximum lateral dimension of the cylindrical portion.
7. The three-dimensional memory device of claim 1 , further comprising second contact via structures vertically extending through the second-tier retro-stepped dielectric material portion, contacting a respective cylindrical sidewall of the second-tier retro-stepped dielectric material portion, and contacting a top surface of a respective one of the second electrically conductive layers.
8. The three-dimensional memory device of claim 7 , wherein top surfaces of the first contact via structures, top surfaces of the second contact via structures, and annular top surfaces of the tubular insulating liners are located within a same horizontal plane.
9. The three-dimensional memory device of claim 1 , wherein:
each layer within the first-tier alternating stack is present underneath the second-tier retro-stepped dielectric material portion within an area that is laterally enclosed by a periphery of the second-tier retro-stepped dielectric material portion; and
each layer within the second-tier alternating stack is present above the first-tier retro-stepped dielectric material portion within an area that is laterally enclosed by a periphery of the first-tier retro-stepped dielectric material portion.
10. The three-dimensional memory device of claim 1 , further comprising second memory stack structures located in a second memory array region in which each layer of the first-tier alternating stack and each layer of the second-tier alternating stack are present, wherein each of the second memory stack structures comprises a respective memory film and a respective vertical semiconductor channel, the second memory array region is laterally spaced from the first memory array region along a first horizontal direction, and the first-tier retro-stepped dielectric material portion and the second retro-stepped dielectric material portion are located between the first memory array region and the second memory array region.
11. The three-dimensional memory device of claim 10 , further comprising:
a first backside trench fill structure laterally extending along a first horizontal direction, laterally contacting the first-tier alternating stack, the second-tier alternating stack, and the first-tier retro-stepped dielectric material portion, and comprising a first portion of a dielectric fill material; and
a second backside trench fill structure laterally extending along the first horizontal direction, laterally spaced from the first backside trench fill structure along a second horizontal direction, laterally contacting the first-tier alternating stack, the second-tier alternating stack, and the second-tier retro-stepped dielectric material portion, and comprising a second portion of the dielectric fill material.
12. The three-dimensional memory device of claim 10 , wherein the second-tier retro-stepped dielectric material portion is laterally offset from the first-tier retro-stepped dielectric material portion along the second horizontal direction.
13. The three-dimensional memory device of claim 10 , wherein:
the first memory array region and the second memory array region are laterally spaced from each other by an inter-array region in which the first-tier retro-stepped dielectric material portion and the second-tier retro-stepped dielectric material portion are located; and
each layer within the first-tier alternating stack and the second-tier alternating stack comprises a respective strip portion located within the inter-array region and laterally extending continuously from the first memory array region to the second memory array region.
14. A method of forming a three-dimensional memory device, comprising:
forming a first-tier structure that includes a first vertically alternating sequence of first continuous insulating layers and first continuous sacrificial material layers and a first-tier retro-stepped dielectric material portion overlying first stepped surfaces of the first vertically alternating sequence over a substrate;
forming sacrificial landing pad structures in an upper region of the first-tier retro-stepped dielectric material portion;
forming a second vertically alternating sequence of second continuous insulating layers and second continuous sacrificial material layers over the first-tier structure;
forming sacrificial pillar structures through the second vertically alternating sequence on the sacrificial landing pad structures;
forming first memory stack structures in a first memory array region in which each layer within the first vertically alternating sequence and the second vertically alternating sequence is present;
forming backside trenches through the second vertically alternating sequence and the first vertically alternating sequence;
replacing patterned portions of the first continuous sacrificial material layers and the second continuous sacrificial material layers with electrically conductive layers; and
replacing the sacrificial pillar structures, the sacrificial landing pad structures, and portions of the first-tier retro-stepped dielectric material portion that underlie the sacrificial landing pad structures with laterally-isolated contact via structures, wherein each of the laterally-isolated contact via structures comprises a respective first contact via structure that contacts a respective one of the electrically conductive layers.
15. The method of claim 14 , further comprising:
forming first contact via cavities by removing the sacrificial pillar structures and the sacrificial landing pad structures; and
forming tubular insulating liners at peripheral portions of the first contact via cavities by conformally depositing and anisotropically etching an insulating material, wherein each of the laterally-isolated contact via structures comprises a respective one of the tubular insulating liners.
16. The method of claim 15 , further comprising:
vertically extending remaining portions of the first contact via cavities by performing an anisotropic etch process that etches regions of the first-tier retro-stepped dielectric material portion that underlie the first contact via cavities, wherein top surfaces of a subset of the electrically conductive layers are physically exposed to the first contact via cavities; and
depositing at least one conductive material in the first contact via cavities, wherein the first contact via structures comprise a respective portion of the at least one conductive material.
17. The method of claim 15 , further comprising:
forming second stepped surfaces by patterning the second vertically alternating sequence, wherein the second stepped surfaces are laterally offset from the first stepped surfaces;
forming a second-tier retro-stepped dielectric material portion overlying the second stepped surfaces of the second vertically alternating sequence; and
forming bit lines extending in a bit line direction over the first memory stack structures;
wherein the second-tier retro-stepped dielectric material portion is laterally offset from the first-tier retro-stepped dielectric material portion along the bit line direction; and
wherein the anisotropic etch process forms second contact via cavities vertically extending through the second-tier retro-stepped dielectric material portion to a respective one of another subset of the electrically conductive layers.
18. The method of claim 14 , further comprising:
forming recess cavities in the upper region of the first-tier retro-stepped dielectric material portion;
forming first-tier memory openings through the first vertically alternating sequence; and
depositing a sacrificial first-tier fill material in the recess cavities and the first-tier memory openings, wherein portions of the sacrificial first-tier fill material filling the recess cavities comprise the sacrificial landing pad structures, and portions of the sacrificial first-tier fill material filling the first-tier memory openings comprise sacrificial first-tier memory opening fill portions.
19. The method of claim 18 , further comprising:
forming pillar cavities through the second vertically alternating sequence on the sacrificial landing pad structures;
forming second-tier memory openings through the second vertically alternating sequence on the sacrificial first-tier memory opening fill portions; and
depositing a sacrificial second-tier fill material in the pillar cavities and the second-tier memory openings, wherein portions of the sacrificial second-tier fill material filling the recess cavities comprise the sacrificial pillar structures, and portions of the sacrificial second-tier fill material filling the second-tier memory openings comprise sacrificial second-tier memory opening fill portions.
20. The method of claim 19 , wherein the pillar cavities and the second-tier memory openings are formed simultaneously by performing an anisotropic etch process, wherein the sacrificial landing pad structures and the sacrificial first-tier memory opening fill portions are employed as etch stop structures for the anisotropic etch process.