STAIRLESS THREE-DIMENSIONAL MEMORY DEVICE WITH LAYER CONTACT VIA STRUCTURES LOCATED ABOVE SUPPORT PILLAR STRUCTURES AND METHODS OF FORMING THE SAME
A three-dimensional memory device includes an alternating stack of insulating layers and electrically conductive layers, a memory opening vertically extending through the alternating stack, a memory opening fill structure located in memory opening and including a vertical stack of memory elements located at levels of the electrically conductive layers and a vertical semiconductor channel, a layer contact via structure contacting a first electrically conductive layer within a first subset of the electrically conductive layers and vertically extending through a second subset of the electrically conductive layers that overlies the first subset, and a support pillar structure located under a bottom surface of the layer contact via structure.
1 . A three-dimensional memory device, comprising:
an alternating stack of insulating layers and electrically conductive layers;
a memory opening vertically extending through the alternating stack;
a memory opening fill structure located in memory opening and comprising a vertical stack of memory elements located at levels of the electrically conductive layers and a vertical semiconductor channel;
a layer contact via structure contacting a first electrically conductive layer within a first subset of the electrically conductive layers and vertically extending through a second subset of the electrically conductive layers that overlies the first subset; and
a first-type support pillar structure located under a bottom surface of the layer contact via structure.
2 . The three-dimensional memory device of claim 1 , wherein:
the first-type support pillar structure contacts a center portion of the bottom surface of the layer contact via structure; and
a bottom surface of the layer contact via structure contacts an annular horizontal surface segment of the first electrically conductive layer.
3 . The three-dimensional memory device of claim 1 , further comprising second-type support pillar structures laterally surrounding the layer contact via structure and having a greater vertical extent than the first-type support pillar structure.
4 . The three-dimensional memory device of claim 3 , further comprising a finned insulating spacer comprising a vertically-extending tubular portion that laterally surrounds the layer contact via structure and a vertical stack of insulating fins that laterally extend outward from the vertically-extending tubular portion at each level of the second subset of the electrically conductive layers.
5 . The three-dimensional memory device of claim 4 , wherein bottom surfaces of the first-type support pillar structure and the second-type support pillar structures are located within a first horizontal plane that underlies the alternating stack.
6 . The three-dimensional memory device of claim 4 , wherein top surfaces of the second-type support pillar structures are located within a horizontal plane including a topmost surface of the alternating stack.
7 . The three-dimensional memory device of claim 4 , wherein a first insulating fin within the vertical stack of insulating fins comprises a plurality of vertically-straight and laterally-concave surface segments that contact the second-type support pillar structures.
8 . The three-dimensional memory device of claim 7 , wherein:
the first insulating fin further comprises a plurality of vertically-straight and laterally-convex surface segments; and
each vertically-straight and laterally-concave surface segment of the plurality of vertically-straight and laterally-concave surface segments is adjoined to a respective pair of vertically-straight and laterally-convex surface segments of the plurality of vertically-straight and laterally-convex surface segments.
9 . The three-dimensional memory device of claim 4 , wherein the vertically-extending tubular portion of the finned insulating spacer is laterally spaced from the second-type support pillar structures and comprises a plurality of cylindrical surface segments that contact a respective one of the insulating layers.
10 . The three-dimensional memory device of claim 4 , wherein a top surface of the layer contact via structure and an annular top surface of the finned insulating spacer are located above a horizontal plane including top surfaces of the second-type support pillar structures.
11 . The three-dimensional memory device of claim 1 , wherein:
the first-type support pillar structure comprises a top surface containing a divot therein; and
the divot is filled with an insulating divot fill material portion that contacts a center potion of a bottom surface of the layer contact via structure.
12 . The three-dimensional memory device of claim 1 , wherein the first-type support pillar structure consists essentially of an insulating material and comprises a first-type dielectric pillar structure.
13 . The three-dimensional memory device of claim 1 , wherein:
the memory opening fill structure further comprises a first blocking dielectric layer and a first dielectric core laterally surrounded by the vertical semiconductor channel; and
the first-type support pillar structure comprises a second blocking dielectric layer having a same material composition as the first blocking dielectric layer and second dielectric core laterally surrounded by and contacting the second blocking dielectric layer.
14 . The three-dimensional memory device of claim 1 , wherein:
the memory opening fill structure further comprises a first dielectric core laterally surrounded by the vertical semiconductor channel, a drain region, and a memory film comprising a blocking dielectric layer, a memory material layer comprising the vertical stack of memory elements, and a tunneling dielectric layer; and
the first-type support pillar structure comprises a dummy semiconductor channel, a second dielectric core laterally surrounded by and contacting the dummy semiconductor channel,
a dummy drain region, and a dummy memory film comprising a dummy blocking dielectric layer, a dummy memory material layer, and a dummy tunneling dielectric layer.
15 . The three-dimensional memory device of claim 1 , wherein:
the bottom surface of the layer contact via structure comprises a center portion and a peripheral portion located below the center portion;
the first-type support pillar structure contacts the center portion of the bottom surface of the layer contact via structure;
a top surface of the first-type support pillar structure is located above the peripheral portion of the bottom surface of the layer contact via structure; and
a tubular insulating spacer surrounds a top portion of the first-type support pillar structure.
16 . A method of forming a memory device, comprising:
forming an alternating stack of insulating layers and sacrificial material layers over a substrate;
forming support pillar structures through the alternating stack, wherein the support pillar structures comprise a first-type support pillar structure and second-type support pillar structures that laterally surround the first-type support pillar structure;
forming a memory opening through the alternating stack;
forming a memory opening fill structure in the memory opening, wherein the memory opening fill structure comprises a vertical stack of memory elements located at levels of the sacrificial material layers and a vertical semiconductor channel;
forming a contact via cavity by vertically recessing the first-type support pillar structure and a neighboring portion of the alternating stack, wherein a remaining portion of the first-type support pillar structure is located below the contact via cavity;
replacing the sacrificial material layers with electrically conductive layers; and
forming a layer contact via in the contact via cavity on a first electrically conductive layer of the electrically conductive layers.
17 . The method of claim 16 , further comprising:
isotropically recessing physically exposed sidewalls of the sacrificial material layers around the contact via cavity to form a finned contact via cavity; and
forming a finned insulating spacer comprising a vertically-extending tubular portion and a vertical stack of insulating fins that laterally extend outward from the vertically-extending tubular portion at a peripheral region of a volume of the finned contact via cavity, wherein the layer contact via structure is formed within a volume that is laterally surrounded by the finned insulating spacer.
18 . The method of claim 16 , wherein the support pillar structures are formed prior to or after formation of the memory opening fill structure, and consist essentially of a dielectric fill material.
19 . The method of claim 16 , further comprising:
forming support openings through the alternating stack concurrently with formation of the memory opening;
forming a continuous blocking dielectric layer, a continuous memory material layer, a continuous tunneling dielectric layer, and a continuous semiconductor channel material layer in each of the memory opening and the support openings and over the alternating stack; and
removing portions of the continuous blocking dielectric layer, the continuous memory material layer, the continuous tunneling dielectric layer, and the continuous semiconductor channel material layer located over the alternating stack to form the vertical semiconductor channel and a memory film comprising a blocking dielectric layer, a memory material layer comprising the vertical stack of memory elements, and a tunneling dielectric layer in the memory opening, and to form the support pillar structures each comprising a dummy semiconductor channel and dummy memory film comprising a dummy blocking dielectric layer, a dummy memory material layer, and a dummy tunneling dielectric layer in the support openings.
20 . The method of claim 16 , further comprising forming etch-resistant cap plates above each of the first-type support pillar structures, wherein a top portion of each of the first-type support pillar structures is located above a bottom surface of the contact via cavity.