Three-dimensional memory device with self-aligned multi-level drain select gate electrodes
Sacrificial memory opening fill structures are formed through an alternating stack of insulating layers and sacrificial material layers. A drain select level isolation trench extending through drain select level sacrificial material layers is formed employing a combination of a photoresist layer including a linear opening and a pair of rows of sacrificial memory opening fill structures as an etch mask. Sacrificial spacers are formed on sidewalls of the drain select level isolation trench. A drain select level isolation dielectric structure is formed in a remaining volume of the drain select level isolation trench. The sacrificial memory opening fill structures are replaced with memory stack structures. The sacrificial material layers and the sacrificial spacers are replaced with a conductive material to form electrically conductive layers and conductive connector spacers. The drain select level isolation dielectric structure is self-aligned to the memory stack structures and divides drain select level electrically conductive layers.
1. A three-dimensional memory device comprising:
an alternating stack of insulating layers and electrically conductive layers located over a substrate;
a drain select level isolation dielectric structure; and
memory stack structures extending through the alternating stack, wherein each of the memory stack structures comprises a memory film and a vertical semiconductor channel contacting an inner sidewall of the memory film,
wherein:
two or more uppermost layers among the electrically conductive layers include first strip portions and second strip portions that are laterally spaced from one another by the drain select level isolation dielectric structure; and
the drain select level isolation dielectric structure includes a pair of alternating sequences of non-concave sidewall portions and concave sidewall portions.
2. The three-dimensional memory device of claim 1 , the pair of alternating sequences of non-concave sidewall portions and concave sidewall portions comprises:
a first alternating sequence of first planar sidewall portions and first concave sidewall portions; and
a second alternating sequence of second planar sidewall portions and second concave sidewall portions,
wherein:
the first planar sidewall portions are located within a first vertical plane; and
the second planar sidewall portions are located within a second vertical plane that is parallel to the first vertical plane.
3. The three-dimensional memory device of claim 1 , wherein:
each of the concave sidewall portions is equidistant from a sidewall of a respective one of the memory stack structures;
the two or more uppermost layers among the electrically conductive layers comprise drain select level electrically conductive layers; and
a subset of the electrically conductive layers that underlies the two or more uppermost layers among the electrically conductive layers comprises word line electrically conductive layers of the memory stack structures.
4. The three-dimensional memory device of claim 1 , further comprising:
a first conductive connector spacer connected to each of the first strip portions of the two or more uppermost layers among the electrically conductive layers; and
a second conductive connector spacer connected to each of the second strip portions of the two or more uppermost layers among the electrically conductive layers.
5. The three-dimensional memory device of claim 4 , wherein each of the first and second conductive connector spacers includes an alternating sequence of conductive non-concave sidewall portions and conductive concave sidewall portions.
6. The three-dimensional memory device of claim 4 , wherein the first and second conductive connector spacers comprise a same material as the electrically conductive layers.
7. The three-dimensional memory device of claim 4 , further comprising a backside blocking dielectric layer including horizontal portions located between each neighboring pair of the insulating layers and the electrically conductive layers and vertical portions located between the drain select level isolation dielectric structure and the first and second conductive connector spacers.
8. The three-dimensional memory device of claim 7 , wherein the backside blocking dielectric layer further comprises additional vertical portions contacting sidewalls of a subset of the insulating layers located between a bottommost layer among the two or more uppermost layers among the electrically conductive layers and a topmost layer among the two or more uppermost layers among the electrically conductive layers.
9. The three-dimensional memory device of claim 4 , wherein:
the first conductive connector spacer and the first strip portions of the two or more uppermost layers among the electrically conductive layers constitute a first continuous conductive structure; and
the second conductive connector spacer and the second strip portions of the two or more uppermost layers among the electrically conductive layers constitute a second continuous conductive structure.
10. The three-dimensional memory device of claim 1 , further comprising a pair of backside trenches vertically extending through the alternating stack and laterally extending along a lengthwise direction of the drain select level isolation dielectric structure,
wherein:
the first strip portions are located between the drain select level isolation dielectric structure and one of the pair of backside trenches; and
the second strip portions are located between the drain select level isolation dielectric structure and another of the pair of backside trenches.
11. The three-dimensional memory device of claim 1 , wherein:
the three-dimensional memory device comprises a monolithic three-dimensional NAND memory device;
a subset of the electrically conductive layers comprises, or is 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, and the plurality of control gate electrodes comprises 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
a plurality of charge storage elements, each charge storage element located adjacent to a respective one of the plurality of semiconductor channels.
12. A three-dimensional memory device comprising:
an alternating stack of insulating layers and electrically conductive layers located over a substrate;
memory stack structures extending through the alternating stack, wherein each of the memory stack structures comprises a memory film and a vertical semiconductor channel contacting an inner sidewall of the memory film;
a first conductive connector spacer connected to each of first strip portions of two or more uppermost layers among the electrically conductive layers; and
a second conductive connector spacer connected to each of second strip portions of the two or more uppermost layers among the electrically conductive layers,
wherein each of the first and second conductive connector spacers includes an alternating sequence of conductive non-concave sidewall portions and conductive concave sidewall portions.