Three-dimensional memory device including stairless word line contact structures and method of making the same
A three-dimensional memory device includes an alternating stack of insulating layers and electrically conductive layers, memory openings located in a memory array region and vertically extending through the alternating stack, memory opening fill structures located in the memory openings, and laterally-isolated contact via assemblies located in a contact region that is located adjacent to the memory array region. Each of the laterally-isolated contact via assemblies includes a contact via structure contacting a top surface of a respective one of the electrically conductive layers and a dielectric spacer laterally surrounding the contact via structure. Each contact via structure other than a contact via structure contacting a topmost one of the electrically conductive layers extends through and is laterally surrounded by each electrically conductive layer that overlies the respective electrically conductive layer.
1 . A three-dimensional memory device, comprising:
an alternating stack of insulating layers and electrically conductive layers located over a substrate;
memory openings located in a memory array region and vertically extending through the alternating stack;
memory opening fill structures located in the memory openings;
laterally-isolated contact via assemblies located in a contact region that is located adjacent to the memory array region, wherein each of the laterally-isolated contact via assemblies comprises a contact via structure contacting a top surface of a respective one of the electrically conductive layers and an insulating spacer laterally surrounding the contact via structure;
first support pillar structures comprising a respective first portion of a dielectric material, located in the contact region, vertically extending through each layer within the alternating stack, and having a respective top surface located within a horizontal plane overlying the alternating stack; and
second support pillar structures comprising second portions of the dielectric material and located in the contact region and having a lesser height than the first support pillar structures;
wherein:
each contact via structure other than a contact via structure contacting a topmost one of the electrically conductive layers extends through and is laterally surrounded by each electrically conductive layer that overlies the respective electrically conductive layer;
bottom surfaces of the first support pillar structures and the second support pillar structures are located within a first horizontal plane;
top surfaces the second support pillar structures are more proximal to the first horizontal plane than top surfaces of the first support pillar structures;
top surfaces of the second support pillar structures contacts a bottom surface segment of an overlying contact via structure of the contact via structures;
the bottom surface segment of the overlying contact via structure is located above a horizontal plane including an interface between the overlying contact via structure and the respective one of the electrically conductive layers; and
a contact area between the overlying contact via structure and the respective one of the electrically conductive layers encircles a contact area between a respective one of the second support pillar structures and the overlying contact via structure in a plan view.
2 . The three-dimensional memory device of claim 1 , wherein the alternating stack is free of stepped surfaces within the contact region.
3 . The three-dimensional memory device of claim 1 , wherein the insulating spacer is vertically spaced from the respective one of the electrically conductive layers by a respective one of the insulating layers.
4 . The three-dimensional memory device of claim 1 , wherein the insulating spacer has an outer surface having a corrugated vertical cross-sectional profile in which first portions of the insulating spacer located at levels of the electrically conductive layers laterally protrude outward relative to second portions of the insulating spacer located at levels of the insulating layers.
5 . The three-dimensional memory device of claim 4 , wherein, for at least one of the insulating spacers:
a bottommost one of the first portions has a convex sidewall; and
each of the first portions that overlies the bottommost one of the first portions has a vertical sidewall.
6 . The three-dimensional memory device of claim 1 , further comprising an annular insulating spacer comprising a same material as the insulating layers and laterally surrounding an upper tip of one of the second support pillar structures.
7 . The three-dimensional memory device of claim 6 , wherein the annular insulating spacer contacts the bottom surface segment of the overlying contact via structure and a cylindrical sidewall surface segment of the overlying contact via structure.
8 . The three-dimensional memory device of claim 7 , wherein:
the insulating spacer comprises first portions located at levels of the electrically conductive layers and second portions located at levels of the insulating layers; and
a lateral distance between an inner periphery of a bottom surface of the annular insulating spacer and an outer periphery of the bottom surface of the annular insulating spacer is the same as a lateral distance between an inner sidewall and an outer sidewall of each of the second portions of the insulating spacer.
9 . The three-dimensional memory device of claim 1 , wherein the insulating spacer comprises a straight cylindrical inner sidewall that vertically extends from a bottommost surface of the insulating spacer to a topmost surface of the insulating spacer.
10 . The three-dimensional memory device of claim 1 , wherein each of the memory opening fill structures comprises a vertical semiconductor channel and a memory film.