Three-dimensional memory device containing through-memory-level contact via structures
A contact via structure vertically extending through an alternating stack of insulating layers and electrically conductive layers is provided in a staircase region having stepped surfaces. The contact via structure is electrically isolated from each electrically conductive layer of the alternating stack except for an electrically conductive layer that directly underlies a horizontal interface of the stepped surfaces. A laterally-protruding portion of the contact via structure contacts an annular top surface of the electrically conductive layer. The electrical isolation can be provided by a ribbed insulating spacer that includes laterally-protruding annular rib regions at levels of the insulating layers, or can be provided by annular insulating spacers located at levels of the electrically conductive layers. The contact via structure can contact a top surface of an underlying metal interconnect structure that overlies a substrate to provide an electrically conductive path.
1. A device structure comprising:
an alternating stack of insulating layers and electrically conductive layers located over a substrate and including stepped surfaces in a staircase region;
a retro-stepped dielectric material portion overlying the stepped surfaces of the alternating stack;
lower-level metal interconnect structures embedded in lower-level dielectric material layers and located between the substrate and the alternating stack; and
a laterally-insulated via structure vertically extending through the alternating stack and the retro-stepped dielectric material portion,
wherein the laterally-insulated via structure comprises:
a ribbed insulating spacer comprising a neck portion that extends through the alternating stack, and laterally-protruding annular rib regions extending from the neck portion at each level of insulating layers; and
a conductive via structure extending through the neck portion of the ribbed insulating spacer and contacting one of the electrically conductive layers;
wherein the conductive via structure is a column-shaped conductive via structure that comprises:
a conductive shaft portion extending through the neck portion of the ribbed insulating spacer;
a conductive capital portion overlying the conductive shaft portion, and contacting a topmost electrically conductive layer through which the conductive via structure extends; and
a conductive base portion underlying a bottommost electrically conductive layer through which the conductive via structure extends;
wherein:
the column-shaped conductive via structure comprises a downward protruding conductive portion that protrudes downward from the conductive base portion and having a lesser lateral extent than the conductive base portion and contacting a top surface of one of the lower-level metal interconnect structures; and
the ribbed insulating spacer includes an annular bottom opening through which the downward protruding conductive portion vertically extends.
2. The device structure of claim 1 , wherein the conductive capital portion and the conductive base portion have greater lateral extents than the conductive shaft portion.
3. The device structure of claim 1 , wherein outer sidewalls of the laterally-protruding annular rib regions are laterally offset outward from a vertical sidewall of the neck portion by a same lateral offset distance.
4. The device structure of claim 1 , wherein the ribbed insulating spacer includes a cylindrical portion underlying a subset of the electrically conductive layers through which the conductive via structure extends, and laterally surrounding the conductive base portion.
5. The device structure of claim 1 , wherein:
a contact area between the conductive capital portion and a top surface of the topmost electrically conductive layer is located between an outer periphery of a bottom surface of the conductive capital portion and an inner periphery of the bottom surface of the conductive capital portion; and
the outer periphery of the bottom surface of the conductive capital portion is laterally offset from the inner periphery of the bottom surface of the conductive capital portion by a uniform lateral offset distance.
6. The device structure of claim 5 , wherein:
a sidewall of the conductive capital portion contacts an upper portion of a sidewall of the topmost electrically conductive layer; and
a bottommost surface of the conductive capital portion contacts a top surface of the ribbed insulating spacer.
7. The device structure of claim 5 , further comprising a cylindrical insulating spacer laterally surrounding the conductive capital portion and overlying the topmost electrically conductive layer and comprising a same dielectric material as the ribbed insulating spacer.
8. The device structure of claim 1 , further comprising:
memory stack structures extending through the alternating stack, wherein each of the memory stack structures comprises a vertical stack of charge storage elements, a tunneling dielectric layer laterally surrounded by the vertical stack of charge storage elements, and a vertical semiconductor channel laterally surrounded by the tunneling dielectric layer; and
driver circuitry containing a metal interconnect structure located below the alternating stack, wherein the conductive via structure physically contacts the metal interconnect structure located below the alternating stack.
9. The device structure of claim 8 , wherein:
the device structure comprises a monolithic three-dimensional NAND memory device;
the electrically conductive layers comprise, or are electrically connected to, a respective word line of the monolithic three-dimensional NAND memory device;
the substrate comprises a silicon substrate;
the monolithic three-dimensional NAND memory device comprises an array of monolithic three-dimensional NAND strings over the silicon substrate;
at least one memory cell in a first device level of the array of monolithic three-dimensional NAND strings is located over another memory cell in a second device level of the array of monolithic three-dimensional NAND strings;
the silicon substrate contains an integrated circuit comprising a driver circuit for the memory device located thereon;
the electrically conductive layers comprise a plurality of control gate electrodes having a strip shape extending substantially parallel to the top surface of the substrate;
the plurality of control gate electrodes comprise at least a first control gate electrode located in the first device level and a second control gate electrode located in the second device level; and
the array of monolithic three-dimensional NAND strings comprises:
a plurality of semiconductor channels, wherein at least one end portion of each of the plurality of semiconductor channels extends substantially perpendicular to a top surface of the substrate, and one of the plurality of semiconductor channels including the vertical semiconductor channel, and
a plurality of charge storage elements, each charge storage element located adjacent to a respective one of the plurality of semiconductor channels.
10. A device structure comprising:
an alternating stack of insulating layers and electrically conductive layers located over a substrate and including stepped surfaces in a staircase region;
a retro-stepped dielectric material portion overlying the stepped surfaces of the alternating stack; and
a laterally-insulated via structure vertically extending through the alternating stack and the retro-stepped dielectric material portion,
wherein the laterally-insulated via structure comprises:
a ribbed insulating spacer comprising a neck portion that extends through the alternating stack, and laterally-protruding annular rib regions extending from the neck portion at each level of insulating layers; and
a conductive via structure extending through the neck portion of the ribbed insulating spacer and contacting one of the electrically conductive layers;
wherein the conductive via structure is a column-shaped conductive via structure that comprises:
a conductive shaft portion extending through the neck portion of the ribbed insulating spacer;
a conductive capital portion overlying the conductive shaft portion, and contacting a topmost electrically conductive layer through which the conductive via structure extends; and
a conductive base portion underlying a bottommost electrically conductive layer through which the conductive via structure extends;
wherein:
a contact area between the conductive capital portion and a top surface of the topmost electrically conductive layer is located between an outer periphery of a bottom surface of the conductive capital portion and an inner periphery of the bottom surface of the conductive capital portion; and
the outer periphery of the bottom surface of the conductive capital portion is laterally offset from the inner periphery of the bottom surface of the conductive capital portion by a uniform lateral offset distance.
11. The device structure of claim 10 , wherein:
a sidewall of the conductive capital portion contacts an upper portion of a sidewall of the topmost electrically conductive layer; and
a bottommost surface of the conductive capital portion contacts a top surface of the ribbed insulating spacer.
12. The device structure of claim 10 , further comprising a cylindrical insulating spacer laterally surrounding the conductive capital portion and overlying the topmost electrically conductive layer and comprising a same dielectric material as the ribbed insulating spacer.