Memory die with source side of three-dimensional memory array bonded to logic die and methods of making the same

1. A three-dimensional memory device comprising a memory die, wherein the memory die comprises:

an alternating stack of insulating layers and electrically conductive layers located between a drain-side dielectric layer and a source-side dielectric layer, wherein the electrically conductive layers comprise at least one drain side select gate electrode, at least one source side select gate electrode, and word lines located between the at least one drain side select gate electrode and the at least one source side select gate electrode;

backside trench fill structures vertically extending through the word lines, laterally extending along a first horizontal direction, and laterally spaced apart along a second horizontal direction;

backside dielectric rails vertically extending through the at least one drain side select gate electrode and contacting, and overlying or underlying, a respective one of the backside trench fill structures;

memory openings vertically extending through the alternating stack between neighboring pairs of the backside trench fill structures and between neighboring pairs of the backside dielectric rails; and

memory opening fill structures located in the memory openings, wherein each of the memory opening fill structures comprises a vertical semiconductor channel and a vertical stack of memory elements located at the word lines of the electrically conductive layers,

wherein each of the backside dielectric rails has a respective trapezoidal vertical cross-sectional profile within a vertical plane that is perpendicular to the first horizontal direction, and has a greater width than the respective one of the backside trench fill structures.

2. The three-dimensional memory device of claim 1 , wherein each of the memory openings has a greater lateral dimension at an interface with the source-side dielectric layer than at an interface with the drain-side dielectric layer.

3. The three-dimensional memory device of claim 1 , wherein each of the backside dielectric rails has a lesser width within a horizontal plane including an interface with the drain-side dielectric layer than within a horizontal plane including an interface with the respective one of the backside trench fill structures.

4. The three-dimensional memory device of claim 1 , wherein the memory die further comprises drain-select-level isolation structures vertically extending through the at least one drain side select gate electrode, located between a respective pair of the backside dielectric rails, and contacting the drain-side dielectric layer.

5. The three-dimensional memory device of claim 4 , wherein:

the at least one drain side select gate electrode comprises a plurality of drain side select gate electrodes that are vertically spaced apart by a subset of the insulating layers; and

the memory die further comprises drain-select-level conductive strips contacting a respective one of the drain-select-level isolation structures and electrically connecting multiple drain side select gate electrodes that are vertically spaced apart.

6. The three-dimensional memory device of claim 1 , wherein each of the memory opening fill structures further comprises a drain region contacting a respective one of the vertical semiconductor channels.

7. The three-dimensional memory device of claim 6 , wherein the memory die further comprises drain contact via structures embedded in the drain-side dielectric layer and contacting a respective one of the drain regions.

8. The three-dimensional memory device of claim 7 , wherein the memory die further comprises bit lines embedded in a bit-line-level dielectric layer, laterally extending along the second horizontal direction, and electrically connected to a respective subset of the drain contact via structures.

9. The three-dimensional memory device of claim 1 , wherein the memory die further comprises a source layer contacting end surfaces of the vertical semiconductor channels and embedded in the source-side dielectric layer.

10. The three-dimensional memory device of claim 9 , wherein the memory die further comprises memory-side dielectric material layers embedding memory-side metal interconnect structures and located on the source-side dielectric layer.

11. The three-dimensional memory device of claim 1 , further comprising a logic die including a peripheral circuit and bonded to a source-side dielectric layer side of the memory die.

12. The three-dimensional memory device of claim 1 , wherein:

each of the memory opening fill structures comprises a memory film including a layer stack that comprises a tunneling dielectric layer and a charge storage layer; and

each of the vertical stacks of memory elements comprises portions of a respective one of charge storage layers that are located at levels of the word-line-level electrically conductive layers.

13. A method of forming a semiconductor structure, comprising:

forming a first layer stack including at least one first insulating layer and at least one first sacrificial material layer over a substrate;

forming backside dielectric rails vertically extending through the at least one first insulating layer and the at least one first sacrificial material layer;

forming a second layer stack including second insulating layers and second sacrificial material layers over the first layer stack;

forming memory openings through the second layer stack and the first layer stack;

forming memory opening fill structures in the memory openings, wherein each of the memory opening fill structures comprises a memory film and a vertical semiconductor channel;

replacing the second sacrificial material layers with word lines and at least one source side select gate electrode;

removing the substrate selective to the first layer stack;

replacing the at least one first sacrificial material layer with at least one drain side select gate electrode;

forming a source layer on first end surfaces of the vertical semiconductor channels over an alternating stack of the second insulating layers and the word lines of the electrically conductive layers;

forming at least one memory-side dielectric material layer embedding memory-side metal interconnect structures and memory-side bonding pads over the source layer to provide a memory die; and

bonding a logic die comprising a peripheral circuit to a memory-side dielectric material layer side of the memory die, wherein the step of removing substrate occurs after bonding the logic die to the memory die.

14. A method of forming a semiconductor structure, comprising:

forming a first layer stack including at least one first insulating layer and at least one first sacrificial material layer over a substrate;

forming backside dielectric rails vertically extending through the at least one first insulating layer and the at least one first sacrificial material layer;

forming a second layer stack including second insulating layers and second sacrificial material layers over the first layer stack;

forming memory openings through the second layer stack and the first layer stack;

forming memory opening fill structures in the memory openings, wherein each of the memory opening fill structures comprises a memory film and a vertical semiconductor channel;

replacing the second sacrificial material layers with word lines and at least one source side select gate electrode;

removing the substrate selective to the first layer stack;

replacing the at least one first sacrificial material layer with at least one drain side select gate electrode;

forming backside trenches through the second layer stack, wherein a surface of a respective one of the backside dielectric rails is physically exposed at a bottom of each of the backside trenches;

forming backside recesses by removing the second sacrificial material layers selective to the second insulating layers by providing an isotropic etchant into the backside trenches; and

depositing at least one conductive material in the backside recesses to form the word lines and the at least one source side select gate electrode.

15. A method of forming a semiconductor structure, comprising:

forming a first layer stack including at least one first insulating layer and at least one first sacrificial material layer over a substrate;

forming backside dielectric rails vertically extending through the at least one first insulating layer and the at least one first sacrificial material layer;

forming a second layer stack including second insulating layers and second sacrificial material layers over the first layer stack;

forming memory openings through the second layer stack and the first layer stack;

forming memory opening fill structures in the memory openings, wherein each of the memory opening fill structures comprises a memory film and a vertical semiconductor channel;

replacing the second sacrificial material layers with word lines and at least one source side select gate electrode;

removing the substrate selective to the first layer stack;

replacing the at least one first sacrificial material layer with at least one drain side select gate electrode;

forming drain-select-level sacrificial rail structures through the first layer stack, wherein the second layer stack is formed on the drain-select-level sacrificial rail structures;

forming drain-select-level isolation trenches by removing the drain-select-level sacrificial rail structures selective to the at least one first insulating layer; and

forming drain-select-level isolation structures and drain-select-level conductive strips in the drain-select-level isolation trenches.