Three-dimensional memory device employing thinned insulating layers and methods for forming the same
A three-dimensional memory device includes an alternating stack of word lines and at least one insulating layers or air gaps located over a substrate, a memory opening fill structure extending through the alternating stack. The memory opening fill structure includes a memory film and a vertical semiconductor channel contacting an inner sidewall of the memory film. The word lines are thicker than the insulating layers or air gaps.
1. A three-dimensional memory device comprising:
an alternating stack of insulating layers and electrically conductive layers located over a substrate;
a memory opening vertically extending through the alternating stack; and
a memory opening fill structure vertically extending through the alternating stack, wherein:
the memory opening fill structure comprises a memory film and a vertical semiconductor channel contacting an inner sidewall of the memory film; and
the memory film comprises, from outside to inside: a vertical stack of silicon oxide material portions located at levels of a subset of the insulating layers; a vertical stack of silicon oxide blocking dielectric portions that is interlaced with a vertical stack of silicon nitride material portions; a charge storage layer, and a tunneling dielectric layer.
2. The three-dimensional memory device of claim 1 , wherein each of the silicon oxide blocking dielectric portions has a respective outer cylindrical sidewall and a respective inner cylindrical sidewall having a lesser vertical extent than the respective outer cylindrical sidewall.
3. The three-dimensional memory device of claim 2 , wherein the respective inner cylindrical sidewall of each of the silicon oxide blocking dielectric portions is connected to the respective outer cylindrical sidewall of each of the silicon oxide blocking dielectric portions by a respective upper annular interconnection surface and by a respective lower annular interconnection surface.
4. The three-dimensional memory device of claim 3 , wherein:
the respective upper annular interconnection surface and the respective lower annular interconnection surface have tapered convex surfaces that contact a respective tapered concave surface of a respective silicon nitride material portion within the vertical stack of silicon nitride material portions;
each of the silicon oxide blocking dielectric portions comprises interfacial regions adjacent to the respective upper annular interconnection surface and the respective lower annular interconnection surface; and
each of the interfacial regions comprises nitrogen atoms at an atomic concentration less than 1%, the atomic concentration decreasing with a distance from the respective upper annular interconnection surface or with a distance from the respective lower annular interconnection surface.
5. The three-dimensional memory device of claim 1 , wherein a silicon oxide material portion within the vertical stack of silicon oxide material portions comprises:
a vertical cylindrical outer sidewall;
a vertical cylindrical inner sidewall that is laterally offset inward from the vertical cylindrical outer sidewall by a uniform lateral offset distance; and
a pair of tapered concave annular surfaces that connects the vertical cylindrical outer sidewall to the vertical cylindrical inner sidewall.
6. The three-dimensional memory device of claim 5 , wherein:
the silicon oxide material portion within the vertical stack of silicon oxide material portions comprises an outer cylindrical sidewall that contacts an entirety of a cylindrical sidewall of one of the insulating layers;
an upper periphery of the outer cylindrical sidewall of the silicon oxide material portion coincides with an upper periphery of the cylindrical sidewall of the one of the insulating layers; and
a lower periphery of the outer cylindrical sidewall of the silicon oxide material portion coincides with a lower periphery of the cylindrical sidewall of the one of the insulating layers.
7. The three-dimensional memory device of claim 5 , wherein the silicon oxide material portion contacts an entirety of an outer cylindrical sidewall of one of the silicon nitride material portions, a portion of an outer cylindrical sidewall of one of the silicon oxide blocking dielectric portions, and a portion of an outer cylindrical sidewall of another of the silicon oxide blocking dielectric portions.
8. The three-dimensional memory device of claim 1 , wherein:
the memory opening fill structure further comprises an additional vertical stack of additional silicon oxide material portions; and
each of the silicon oxide material portions contacts a sidewall of a respective one of the additional silicon oxide material portions and contacts a cylindrical sidewall of a respective one of the insulating layers.
9. The three-dimensional memory device of claim 1 , wherein the charge storage layer has a straight cylindrical sidewall that contacts each inner cylindrical sidewall of the silicon oxide blocking dielectric portions and each inner cylindrical sidewall of the silicon nitride material portions.
10. The three-dimensional memory device of claim 1 , wherein:
each of the electrically conductive layers is spaced from the vertical stack of silicon oxide blocking dielectric portions by a respective backside blocking dielectric layer; and
each backside blocking dielectric layer contacts one of the silicon oxide blocking dielectric portions and at least one of the silicon nitride material portions.
11. The three-dimensional memory device of claim 1 , further comprising air gaps that are at least partially surrounded by the insulating layers.