Support pillar structures for leakage reduction in a three-dimensional memory device
Multiple tier structures including a respective alternating stack of insulating layers and electrically conductive layers is formed over a substrate. A memory opening fill structure extends through the alternating stacks, and includes a vertical semiconductor channel and a memory film. A support pillar structure extends through at least an upper alternating stack, and includes a dummy memory film and a dummy memory film. The support pillar structure may be narrower than the memory opening fill structure at a bottommost layer of the upper alternating stack. Additionally or alternatively, the dummy memory film may be located above a horizontal plane including a topmost surface of a lower alternating stack. Optionally, another support pillar structure including a dielectric material may be provided underneath the support pillar structure in the lower alternating stack. A dielectric material can be provided at levels of the lower alternating stack in a support pillar structure to reduce inter-level leakage current.
1. A three-dimensional memory device, comprising:
a first-tier structure located over a top surface of a substrate, wherein the first-tier structure comprises a first alternating stack of first insulating layers and first electrically conductive layers and a first retro-stepped dielectric material portion overlying first stepped surfaces of the first alternating stack;
a second-tier structure overlying the first-tier structure, wherein the second-tier structure comprises a second alternating stack of second insulating layers and second electrically conductive layers and a second retro-stepped dielectric material portion overlying second stepped surfaces of the second alternating stack;
a memory opening fill structure extending through all layers within the second alternating stack and the first alternating stack, wherein the memory opening fill structure comprises a vertical semiconductor channel and a memory film that extend through the second alternating stack and a subset of layers within the first alternating stack; and
a support pillar structure extending through all layers within the second alternating stack and including a dummy semiconductor channel having a same material composition as the semiconductor channel and including a dummy memory film having a same material composition as the memory film, wherein a bottommost surface of the dummy memory film is located above a horizontal plane including a topmost surface of the first alternating stack.
2. The three-dimensional memory device of claim 1 , wherein the support pillar structure extends through the subset of layers within the first alternating stack.
3. The three-dimensional memory device of claim 2 , wherein the support pillar structure comprises a doped semiconductor material portion contacting a bottom surface of the dummy memory film.
4. The three-dimensional memory device of claim 3 , further comprising an inter-tier dielectric material layer overlying the first-tier structure and underlying the second-tier structure and laterally surrounding, and contacting, the doped semiconductor material portion.
5. The three-dimensional memory device of claim 2 , wherein the support pillar structure comprises at least one dielectric material portion that contacts sidewalls of the subset of layers within the first alternating stack.
6. The three-dimensional memory device of claim 5 , wherein the at least one dielectric material portion laterally surrounds a semiconductor material portion vertically extending through a plurality of first insulating layers and including electrical dopants at a dopant concentration less than 1.0×10 17 /cm 3 .
7. The three-dimensional memory device of claim 6 , wherein the at least one dielectric material portion comprises a conformal dielectric liner having a uniform thickness and continuously extending over the sidewalls of the plurality of first insulating layers.
8. The three-dimensional memory device of claim 6 , wherein the at least one dielectric material portion comprises a plurality of annular dielectric spacers comprising a dielectric oxide of a semiconductor material of the semiconductor material portion.
9. The three-dimensional memory device of claim 6 , further comprising a doped semiconductor material portion contacting a bottom surface of the dummy memory film and contacting a top surface of the semiconductor material portion and including electrical dopants at a dopant concentration in a range from 5.0×10 19 /cm 3 and 2.0×10 21 /cm 3 .
10. The three-dimensional memory device of claim 5 , wherein the at least one dielectric material portion comprises a dielectric pillar structure contacting a bottom surface and a sidewall of the dummy memory film and extending through, and contacting sidewalls of, a plurality of first insulating layers within the first alternating stack.
11. The three-dimensional memory device of claim 1 , further comprising a first-tier support pillar structure underlying the support pillar structure, extending through the first alternating stack, having a partial areal overlap with the support pillar structure in a plan view, and not in direct contact with the support pillar structure.
12. The three-dimensional memory device of claim 1 , wherein:
the memory film comprises a first layer stack including a tunneling dielectric layer, a charge storage layer, and a blocking dielectric layer; and
the dummy memory film comprises a second layer stack including a dummy tunneling dielectric layer having a same thickness and a same composition as the tunneling dielectric layer, a dummy charge storage layer having a same thickness and a same composition as the charge storage layer, and a dummy blocking dielectric layer having a same thickness and a same composition as the blocking dielectric layer.