THREE-DIMENSIONAL MEMORY DEVICE WITH PILLAR SHAPED TRENCH BRIDGE STRUCTURES AND METHODS OF FORMING THE SAME
A three-dimensional memory device includes alternating stacks of insulating layers and electrically conductive layers laterally extending along a first horizontal direction and laterally spaced apart along a second horizontal direction by lateral isolation trenches, arrays of memory openings vertically extending through the alternating stacks, arrays of memory opening fill structures located within the arrays of memory openings and including a respective vertical stack of memory elements and a vertical semiconductor channel, and composite lateral isolation trench fill structures located between a respective neighboring pair of the alternating stacks. Each of the composite lateral isolation trench fill structures includes a dielectric pillar structure which vertically extends at least from first horizontal plane including a bottom of the alternating stacks to a second horizontal plane including a top of the alternating stacks.
1 . A three-dimensional memory device, comprising:
alternating stacks of insulating layers and electrically conductive layers, wherein each of the alternating stacks laterally extends along a first horizontal direction, and the alternating stacks are laterally spaced apart from each other along a second horizontal direction by lateral isolation trenches;
arrays of memory openings, wherein each array of memory openings vertically extends through a respective one of the alternating stacks;
arrays of memory opening fill structures located within the arrays of memory openings, wherein each of the memory opening fill structures comprises a respective vertical stack of memory elements and a vertical semiconductor channel; and
composite lateral isolation trench fill structures located between a respective neighboring pair of the alternating stacks, wherein each of the composite lateral isolation trench fill structures comprises a dielectric pillar structure which vertically extends at least from first horizontal plane including a bottom of the alternating stacks to a second horizontal plane including a top of the alternating stacks.
2 . The three-dimensional memory device of claim 1 , wherein the dielectric pillar structure comprises an elongated dielectric pillar structure that comprises:
a middle portion laterally extending along the first horizontal direction with a uniform width along the second horizontal direction; and
a pair of end portions having a respective vertically-straight and laterally-concave sidewall.
3 . The three-dimensional memory device of claim 2 , wherein each of the composite lateral isolation trench fill structures further comprises at least one source contact via structure having a pair of lengthwise sidewalls that generally extend along the first horizontal direction and having a laterally-undulating width along the second horizontal direction that undulates along the first horizontal direction.
4 . The three-dimensional memory device of claim 3 , wherein each of the at least one source contact via structure is laterally surrounded by a laterally-elongated tubular insulating spacer having an undulating lateral extent along the second horizontal direction as a function of a lateral distance along the first horizontal direction.
5 . The three-dimensional memory device of claim 3 , wherein:
each of the at least one source contact via structure comprises a respective bottom surface contacting a respective row of semiconductor pedestals; and
each of the memory opening fill structures further comprises a respective pedestal channel portion having a same material composition as the semiconductor pedestals.
6 . The three-dimensional memory device of claim 2 , wherein each of the elongated dielectric pillar structures is in contact with a respective pair of laterally-elongated tubular insulating spacers each having an undulating lateral extent along the second horizontal direction as a function of a lateral distance along the first horizontal direction.
7 . The three-dimensional memory device of claim 1 , wherein each of the alternating stacks has a respective stepped surface that underlies and contacts a respective stepped dielectric material portion.
8 . The three-dimensional memory device of claim 7 , wherein the composite lateral isolation trench fill structures comprise:
first composite lateral isolation trench fill structures that are not in direct contact with any of the stepped dielectric material portions; and
second composite lateral isolation trench fill structures that contact a respective one of the stepped dielectric material portions.
9 . The three-dimensional memory device of claim 8 , wherein:
each of the first composite lateral isolation trench fill structures comprises a respective pair of first source contact via structure having a first maximum lateral width along the second horizontal direction; and
each of the second composite lateral isolation trench fill structures comprises a respective additional first source contact via structure having the first maximum lateral width along the second horizontal direction and a second source contact via structure having a second maximum lateral width along the second horizontal direction that is greater than the first maximum lateral width.
10 . The three-dimensional memory device of claim 7 , wherein a contiguous set of the stepped surfaces continuously extends at least from a bottommost electrically conductive layer within one of the alternating stacks to a topmost electrically conductive layer within said one of the alternating stacks.
11 . The three-dimensional memory device of claim 7 , further comprising layer contact via structures vertically extending through a respective one of the stepped dielectric material portions and contacting a respective electrically conductive layer within the alternating stacks.
12 . The three-dimensional memory device of claim 7 , further comprising dielectric support pillar structures vertically extending through a respective one of the stepped dielectric material portions, wherein the dielectric support pillar structures and the dielectric pillar structures comprise a same dielectric fill material.
13 . The three-dimensional memory device of claim 7 , wherein a subset of the dielectric pillar structures is in direct contact with a respective pair of the alternating stacks and a respective pair of the stepped dielectric material portions.
14 . A method of forming memory device, comprising:
forming a vertically alternating sequence of continuous insulating layers and continuous sacrificial material layers;
forming elongated dielectric pillar structures laterally extending along a first horizontal direction and laterally spaced apart along a second horizontal direction through the vertically alternating sequence;
forming memory openings through the vertically alternating sequence;
forming memory opening fill structures in the memory openings, wherein each of the memory opening fill structures comprises a respective vertical stack of memory elements and a vertical semiconductor channel;
forming laterally-extending trenches through the vertically alternating stack, wherein contiguous combinations of the elongated dielectric pillar structures and the laterally extending trenches divide the vertically alternating sequence into alternating stacks of insulating layers and sacrificial material layers; and
replacing the sacrificial material layers with electrically conductive layers.
15 . The method of claim 14 , wherein the forming the laterally-extending trenches comprises:
forming rows of isolation openings through the vertically alternating sequence; and
isotropically expanding volumes of the isolation openings by isotropically laterally recessing portions of the vertically alternating sequence around the rows of isolation openings to form the laterally-extending trenches.
16 . The method of claim 15 , wherein each of the laterally-extending trenches generally extends along the first horizontal direction and has a lateral width undulation along the second horizontal direction as a function of a lateral distance along the first horizontal direction.
17 . The method of claim 15 , wherein a subset of the isolation openings is formed by etching a peripheral portion of a respective one of the elongated dielectric pillar structures.
18 . The method of claim 14 , further comprising:
forming multiple sets of stepped surfaces by patterning the vertically alternating sequence; and
forming stepped dielectric material portions over the multiple sets of stepped surfaces, wherein:
a first subset of the elongated dielectric pillar structures is formed through a respective one of the stepped dielectric material portions; and
a second subset of the elongated dielectric pillar structures is laterally spaced from the stepped dielectric material portions.
19 . The method of claim 18 , wherein a subset of the laterally-extending trenches is formed through a respective one of the stepped dielectric material portions and divides the respective one of the stepped dielectric material portions into a respective pair of patterned stepped dielectric material portions.
20 . The method of claim 14 , further comprising forming source contact via structures within the laterally-extending trenches.