Three-dimensional memory device with composite charge storage structures and methods for forming the same
A memory device includes an alternating stack of insulating layers and electrically conductive layers located over a substrate, and a memory stack structure extending through the alternating stack. The memory stack structure includes a composite charge storage structure, a tunneling dielectric layer, and a vertical semiconductor channel. The composite charge storage structure may include a vertical stack of tubular charge storage material portions including a first charge trapping material located at levels of the electrically conductive layers, and a charge storage layer including a second charge trapping material extending through a plurality of electrically conductive layers of the electrically conductive layers. The first charge trapping material has a higher charge trap density than the second charge trapping material. Alternatively, the composite charge storage material portions may include discrete charge storage elements each containing a silicon nitride portion and a silicon carbide nitride liner.
1. A memory device comprising:
an alternating stack of insulating layers and electrically conductive layers located over a substrate; and
a memory stack structure extending through the alternating stack, wherein the memory stack structure comprises a vertical stack of discrete charge storage elements that are vertically spaced apart from each other located at levels of the electrically conductive layers, a tunneling dielectric layer located on inner sidewalls of the discrete charge storage elements, and a vertical semiconductor channel contacting an inner sidewall of the tunneling dielectric layer,
wherein each of the discrete charge storage elements comprises:
a silicon nitride portion including an inner sidewall that contacts an outer sidewall of the tunneling dielectric layer; and
a silicon carbide nitride liner in contact with the silicon nitride portion;
further comprising silicon oxide blocking dielectric portions located at each level of the discrete charge storage elements, wherein each of the discrete charge storage elements is laterally spaced from a respective one of the electrically conductive layers by a respective one of the silicon oxide blocking dielectric portions;
wherein each of the discrete charge storage elements further comprises a silicon nitride liner contacting the silicon carbide nitride liner and the outer sidewall of the tunneling dielectric layer;
wherein the silicon nitride liner of each of the discrete charge storage elements contacts a respective overlying one of the insulating layers, and contacts a respective underlying one of the insulating layers; and
wherein the silicon nitride liner of each of the discrete charge storage elements is thinner than the silicon nitride portion.