Methods for forming three-dimensional memory device
Embodiments of three-dimensional (3D) memory devices and methods for forming the same are disclosed. In an example, a method for forming a 3D memory device comprises forming a channel structure extending vertically through a memory stack into a semiconductor layer on a substrate. The memory stack comprises interleaved stack conductive layers and stack dielectric layers. The method further comprises forming an insulating structure in an opening extending vertically through the memory stack and at a distance away from the channel structure, and comprising a dielectric layer doped with at least one of hydrogen or an isotope of hydrogen.
1. A method for forming a three-dimensional (3D) memory device, comprising:
forming a channel structure extending vertically through a memory stack into a semiconductor layer on a substrate, wherein the memory stack comprises interleaved stack conductive layers and stack dielectric layers separated from each other by a high-k dielectric layer;
forming an insulating structure in an opening extending vertically through the memory stack and at a distance away from the channel structure, and comprising a dielectric layer doped with at least one of hydrogen or an isotope of hydrogen, wherein the insulating structure is separated from the stack dielectric layers by the high-k dielectric layer; and
forming a blocking cap layer covering an upper end of the insulating structure and between two portions of the high-k dielectric layer, wherein the blocking cap layer is in direct contact with the high-k dielectric layer.
2. The method of claim 1 , further comprising diffusing at least part of the at least one of hydrogen or an isotope of hydrogen to the channel structure.
3. The method of claim 1 , wherein forming the insulating structure comprises sequentially forming a first layer of silicon oxide, the dielectric layer, and a second layer of silicon oxide in the opening.
4. The method of claim 1 , wherein forming the insulating structure comprises sequentially forming a layer of silicon oxide, the dielectric layer, and a layer of polysilicon in the opening.
5. The method of claim 1 , wherein forming the insulating structure comprises sequentially forming a layer of silicon oxide and the dielectric layer in the opening.
6. The method of claim 3 , wherein forming the blocking cap layer comprises forming a silicon oxide cap at the upper end of the insulating structure and between two portions of the high-k dielectric layer for blocking a diffusing direction of the at least one of hydrogen or an isotope of hydrogen.
7. The method of claim 6 , wherein forming the silicon oxide cap comprises:
etching back a top portion of at least the dielectric layer to form a recess between the two portions of the high-k dielectric layer; and
depositing a layer of silicon oxide to fill the recess.
8. The method of claim 3 , wherein forming the dielectric layer comprises:
depositing a layer of silicon nitride; and
in situ doping the layer of silicon nitride with the least one of hydrogen or an isotope of hydrogen.
9. The method of claim 3 , wherein forming the dielectric layer comprises:
depositing a layer of silicon nitride; and
after the deposition, annealing the layer of silicon nitride in a presence of the least one of hydrogen or an isotope of hydrogen.
10. The method of claim 2 , wherein forming the channel structure comprises:
sequentially forming a first semiconductor layer on the substrate, a sacrificial layer on the first semiconductor layer, and a dielectric stack on the sacrificial layer;
forming the channel structure extending vertically through the dielectric stack and the sacrificial layer into the first semiconductor layer;
forming the opening extending vertically through the dielectric stack;
replacing the sacrificial layer with a second semiconductor layer through the opening; and
replacing the dielectric stack with the memory stack through the opening.
11. The method of claim 10 , wherein forming the channel structure comprises:
forming a channel hole extending vertically through the dielectric stack and the sacrificial layer into the first semiconductor layer; and
sequentially forming a memory film and a semiconductor channel along sidewalls of the channel hole.
12. The method of claim 11 , wherein the diffusing comprises diffusing the at least part of the at least one of hydrogen or an isotope of hydrogen from the dielectric layer to the semiconductor channel.
13. The method of claim 11 , wherein the semiconductor channel comprises polysilicon.
14. The method of claim 1 , wherein the dielectric layer comprises silicon nitride.
15. The method of claim 1 , wherein the semiconductor layer comprises one or more doped silicon layers.
16. The method of claim 1 , wherein the insulating structure extends laterally to separate a plurality of channel structures into a plurality of blocks.
17. The method of claim 1 , further comprising
forming a plurality of channel local contact connected to a plurality of channel structures, respectively; and
forming a first bonding layer above the plurality of channel local contacts.
18. The method of claim 17 , further comprising
forming a second substrate;
forming a peripheral circuit on the second substrate; and
forming a second bonding layer on the peripheral circuit.
19. The method of claim 18 , further comprising bonding the first bonding layer with the second bonding layer.
20. The method of claim 1 , further comprising
removing the substrate to expose the semiconductor layer;
forming one or more insulating layer above the exposed semiconductor layer;
forming a source contact opening extending into the semiconductor layer; and
forming a source contact in the source contact opening, wherein the source contact and the insulating structure are on opposite sides of the semiconductor layer.