Three-dimensional memory device including discrete charge storage elements and methods of forming the same
A memory device includes 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 located in the memory opening and comprising a vertical semiconductor channel and a memory film. The memory film includes a contoured blocking dielectric layer including sac-shaped lateral protrusions located at levels of the electrically conductive layers, a tunneling dielectric layer in contact with the vertical semiconductor channel, and a vertical stack of charge storage material portions located within volumes enclosed by the sac-shaped lateral protrusions.
1. A memory device, comprising:
an alternating stack of insulating layers and electrically conductive layers;
a memory opening vertically extending through the alternating stack; and
a memory opening fill structure located in the memory opening and comprising a vertical semiconductor channel and a memory film;
wherein:
the memory film comprises a tunneling dielectric layer located in contact with the vertical semiconductor channel, and a vertical stack of charge storage material portions that are vertically spaced apart from each other by lateral protrusion portions of a subset of the insulating layers;
the memory film further comprises a contoured blocking dielectric layer including sac-shaped lateral protrusions that protrude outward from a vertical axis passing through a geometrical center of the memory opening and located at levels of the electrically conductive layers;
the vertical stack of charge storage material portions is located between the contoured blocking dielectric layer and the tunneling dielectric layer within volumes enclosed by the sac-shaped lateral protrusions; and
each of the charge storage material portions comprises:
a toroidal central portion recessed outward from a vertical interface between the insulating layers and the memory opening; and
an annular neck portion adjoined to the toroidal central portion, more proximal to the tunneling dielectric layer than the toroidal portion is to the tunneling dielectric layer, and having a lesser vertical extent than the toroidal portion; and
further comprising a charge storage layer, wherein the charge storage layer comprises:
a vertically-extending cylindrical portion that continuously extends vertically through the electrically conductive layers; and
the vertical stack of charge storage material portions which is adjoined to the vertically-extending cylindrical portion at the neck regions of the charge storage material portions.