Three dimensional memory device containing discrete silicon nitride charge storage regions
Discrete silicon nitride portions can be formed at each level of electrically conductive layers in an alternating stack of insulating layers and the electrically conductive layers. The discrete silicon nitride portions can be employed as charge trapping material portions, each of which is laterally contacted by a tunneling dielectric portion on the front side, and by a blocking dielectric portion on the back side. The tunneling dielectric portions may be formed as discrete material portions or portions within a tunneling dielectric layer. The blocking dielectric portions may be formed as discrete material portions or portions within a blocking dielectric layer. The discrete silicon nitride portions can be formed by depositing a charge trapping material layer and selectively removing portions of the charge trapping material layer at levels of the insulating layers. Various schemes may be employed to singulate the charge trapping material layer.
1. A structure comprising:
an alternating stack of insulating layers and electrically conductive layers located over a substrate; and
a memory stack structure extending through a memory opening in the alternating stack and comprising memory elements laterally surrounding a vertical semiconductor channel, wherein:
each of the memory elements comprise, from outside to inside, a blocking dielectric portion that is a region of a continuous blocking dielectric layer, a charge trapping material portion having a vertical sidewall portion and comprising silicon nitride, and a tunneling dielectric portion that is a region of a continuous tunneling dielectric layer directly contacting the continuous blocking dielectric layer, wherein a continuous interface between the continuous blocking dielectric layer and the alternating stack vertically extends through multiple electrically conductive layers of the alternating stack, and a continuous interface between the continuous tunneling dielectric layer and the vertical semiconductor channel vertically extends through the multiple electrically conductive layers of the alternating stack;
each of the insulating layers includes an upper recessed annular rim, a lower recessed annular rim, and an annular center portion located between the upper and lower recessed annular rims, wherein the annular center portion protrudes inward toward a vertical axis of the memory opening relative to the upper and lower recessed rims; and
each of the charge trapping material portions is vertically spaced from one another, and does not contact any other of the charge trapping material portions.
2. The structure of claim 1 , wherein the tunneling dielectric portions are material portions within the continuous tunneling dielectric layer that extends through the alternating stack.
3. The structure of claim 1 , wherein:
the structure comprises a vertical NAND device located in a device region; and
the electrically conductive layers comprise, or are electrically connected to a respective word line of the vertical NAND device.
4. The structure of claim 3 , wherein:
the device region comprises:
a plurality of vertical semiconductor channels, wherein at least one end portion of each of the plurality of vertical semiconductor channels extends substantially perpendicular to a top surface of the substrate;
a plurality of charge storage regions, each charge storage region located adjacent to a respective one of the plurality of vertical semiconductor channels; and
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 a first device level and a second control gate electrode located in a second device level;
the electrically conductive layers in the stack are in electrical contact with the plurality of control gate electrode and extend from the device region to a contact region including the plurality of electrically conductive via connections; and
the substrate comprises a silicon substrate containing a driver circuit for the NAND device.
5. The structure of claim 1 , wherein each of the charge trapping material portions is vertically spaced from one another by a respective interface between the continuous tunneling dielectric layer and the continuous blocking dielectric layer.
6. The structure of claim 5 , wherein the interfaces between the continuous tunneling dielectric layer and the continuous blocking dielectric layer are located at levels of the insulating layers.
7. The structure of claim 1 , wherein:
the continuous blocking dielectric layer undulates inward toward the vertical semiconductor channel at each level of the insulator layers; and
undulates outward away from the vertical semiconductor channel at each level of the electrically conductive layers.
8. The structure of claim 7 , wherein:
each of the charge trapping material portions comprises a sidewall having the vertical portion which comprises a vertical center portion, a tapered upper portion, and a tapered lower portion;
the vertical center portion has a uniform thickness; and
the tapered upper portion and the tapered lower portion has a tapered thickness that decreases with distance from the vertical center portion.
9. The structure of claim 1 , wherein the vertical sidewall portion is a straight portion which extends vertically.
10. The structure of claim 1 , wherein the continuous tunneling dielectric layer comprises an ONO stack.
11. The structure of claim 1 , wherein the continuous blocking dielectric layer comprises aluminum oxide that directly contacts the charge trapping material portions.
12. The structure of claim 1 , wherein:
the continuous blocking dielectric layer comprises silicon oxynitride; and
the continuous tunneling dielectric layer consists essentially of silicon oxide.
13. The structure of claim 1 , wherein:
the continuous blocking dielectric layer consists essentially of silicon oxide; and
the continuous tunneling dielectric layer consists essentially of silicon oxynitride.
14. The structure of claim 1 , wherein:
the continuous blocking dielectric layer consists essentially of silicon oxide, silicon oxynitride, or a combination of silicon oxide and silicon oxynitride; and
the continuous tunneling dielectric layer comprises a dielectric metal oxide.
15. The structure of claim 1 , wherein:
an outer sidewall of the continuous blocking dielectric layer directly contacts each of the insulating layers in the alternating stack;
the outer sidewall of the continuous blocking dielectric layer includes vertical sidewall portions at each level of the electrically conductive layers; and
the vertical sidewall portions of the continuous blocking dielectric protrude inward toward the vertical axis of the memory opening relative to portions of the outer sidewall of the continuous blocking dielectric layer that contact the upper and lower recessed rims.
16. The structure of claim 15 , wherein horizontal surface portions of the outer sidewall of the continuous blocking dielectric layer adjoined to the portions of the outer sidewall of the continuous blocking dielectric layer that contact the upper and lower recessed rims directly contact peripheral portions of top surfaces of the electrically conductive layers and peripheral portions of bottom surfaces of the electrically conductive layers.
17. The structure of claim 15 , wherein:
the electrically conductive layers are vertically spaced from an overlying insulating layer and from an underlying insulating layer by a backside blocking dielectric layer, and is laterally spaced from the continuous blocking dielectric layer by the backside blocking dielectric layer; and
wherein horizontal surface portions of the outer sidewall of the continuous blocking dielectric layer adjoined to the portions of the outer sidewall of the continuous blocking dielectric layer that contact the upper and lower recessed rims directly contact peripheral portions of horizontal surfaces of the backside blocking dielectric layer.