Three-dimensional memory device containing source rails and method of making the same
A three-dimensional memory device includes a source-level structure located over a substrate, an alternating stack of insulating layers and electrically conductive layers located over the source-level structure, memory openings vertically extending through the alternating stack, and memory opening fill structures located in the memory openings. The source-level structure includes a lower source-level semiconductor layer including elongated grooves in an upper portion thereof, doped semiconductor source rails located within the elongated grooves, and an upper source-level semiconductor layer. The doped semiconductor source rails are laterally spaced apart from each other along a first horizontal direction and laterally extend along a second horizontal direction. Each of the memory opening fill structures includes a respective vertical stack of memory elements and a respective vertical semiconductor channel that contacts a respective one of the doped semiconductor source rails.
1 . A three-dimensional memory device, comprising:
a source-level structure located over a substrate and comprising a lower source-level semiconductor layer including elongated grooves in an upper portion thereof, doped semiconductor source rails located within the elongated grooves, an upper source-level semiconductor layer that overlies the lower source-level semiconductor layer and the doped semiconductor source rails, wherein the doped semiconductor source rails are laterally spaced apart from each other along a first horizontal direction and laterally extend along a second horizontal direction, and a plurality of source-level dielectric fill bars laterally extending along the second horizontal direction and enclosed by a respective one of the doped semiconductor source rails;
an alternating stack of insulating layers and electrically conductive layers located over the source-level structure;
memory openings vertically extending through the alternating stack; and
memory opening fill structures located in the memory openings and comprising a respective vertical stack of memory elements and a respective vertical semiconductor channel that contacts a respective one of the doped semiconductor source rails;
a plurality of bit lines which extend in the second horizontal direction and which electrically contact respective vertical semiconductor channels; and
a rows of discrete dielectric backside fill structures extending along the first horizontal direction and connected to the plurality of source-level dielectric fill bars, wherein each of the dielectric backside fill structures contacts sidewalls of each of the insulating layers and each of the electrically conductive layers within the alternating stack.
2 . The three-dimensional memory device of claim 1 , wherein each of the doped semiconductor source rails contacts bottom surfaces of a respective subset of the vertical semiconductor channels within the memory opening fill structures.
3 . The three-dimensional memory device of claim 2 , wherein:
the respective subset of the vertical semiconductor channels within the memory opening fill structures comprises vertical semiconductor channels within two rows of memory opening fill structures;
memory opening fill structures within each row of memory opening fill structures are arranged along the second horizontal direction; and
the two rows of memory opening fill structures are laterally spaced from each other along the first horizontal direction.
4 . The three-dimensional memory device of claim 2 , wherein the bottom surfaces of the respective subset of the vertical semiconductor channels comprise horizontal surfaces located between a horizontal plane including a top surface of the upper source-level semiconductor layer and a horizontal plane including a bottom surface of the upper source-level semiconductor layer.
5 . The three-dimensional memory device of claim 1 , wherein:
the memory opening fill structures are arranged in multiple rows of memory opening fill structures;
memory opening fill structures within each row of memory opening fill structures are arranged with a uniform pitch along the second horizontal direction; and
the multiple rows are laterally spaced apart from each other along the first horizontal direction.
6 . The three-dimensional memory device of claim 5 , wherein:
an upper portion of each of the doped semiconductor source rails has a respective horizontal cross-sectional shape including a pair of lengthwise edges having lateral undulations; and
each of the lengthwise edges have a laterally alternating sequence of straight segments and convex segments that are periodically repeated with a periodicity of the uniform pitch along the second horizontal direction.
7 . The three-dimensional memory device of claim 5 , wherein a lower portion of each of the doped semiconductor source rails has a respective horizontal cross-sectional shape including a pair of straight edges that extend underneath a respective row of memory opening fill structures.
8 . The three-dimensional memory device of claim 1 , wherein:
each of the doped semiconductor source rails comprises two rows of upward-protruding pillar portions; and
each of the upward-protruding pillar portions has a respective cylindrical sidewall that coincides with a bottom portion of a cylindrical sidewall of a respective one of the memory openings.
9 . The three-dimensional memory device of claim 8 , wherein each of the upward-protruding pillar portions comprises a contoured top surface that includes:
a central recessed surface segment in contact with a bottom surface of a respective one of the vertical semiconductor channels;
a cylindrical sidewall surface segment having a bottom periphery that is adjoined to a periphery of the central recessed surface segment and contacting a bottom portion of a sidewall of the respective one of the vertical semiconductor channels; and
an annular surface segment having an inner periphery that is adjoined to a top periphery of the cylindrical sidewall surface segment and having an outer periphery that is adjoined to a sidewall of a respective one of the memory openings.
10 . The three-dimensional memory device of claim 1 , wherein:
each of the memory opening fill structures comprises a dielectric core that is laterally surrounded by the respective vertical semiconductor channel; and
an entirety of each of the dielectric cores is located entirely above a horizontal plane including a bottom surface of the upper source-level semiconductor layer.
11 . The three-dimensional memory device of claim 1 , further comprising:
field effect transistors located on the substrate; and
dielectric material layers overlying the field effect transistors and embedding metal interconnect structures that are electrically connected to the field effect transistors,
wherein the electrically conductive layers are electrically connected to a subset of the field effect transistors through a subset of the metal interconnect structures.