Three-dimensional memory devices and fabricating methods thereof
A three-dimensional (3D) memory device is disclosed. The 3D memory device comprises an alternating layer stack on a substrate, and a top selective gate cut structure having a laminated structure embedded in an upper portion of the alternating layer stack and extending along a lateral direction. The laminated structure of the top selective gate cut structure comprises a dielectric filling wall and a dummy channel and a dummy functional layer on both sides of the dielectric filling wall.
1. A three-dimensional (3D) memory device, comprising:
an alternating layer stack including a plurality of conductive layers on a substrate;
a top selective gate cut structure embedded in an upper portion of the alternating layer stack and extending along a lateral direction;
wherein the top selective gate cut structure comprises:
a dummy channel layer having a semiconductor material, and
a dielectric layer configured to isolate the dummy channel layer from the plurality of conductive layers; and
a plurality of channel structures penetrating the alternating layer stack and arranged as rows parallel to the lateral direction, wherein the top selective gate cut structure is disposed at a location separate from the rows of the plurality of channel structures.
2. The device of claim 1 , wherein the top selective gate cut structure further comprises a dielectric filling wall sandwiched by at least two dummy channel layers.
3. The device of claim 2 , wherein the at least two dummy channel layers are sandwiched by at least two dielectric layers.
4. The device of claim 3 , wherein each of the at least two dielectric layers is a dummy functional layer having a laminated stack.
5. The device of claim 4 , wherein the laminated stack comprises a dummy barrier layer, a dummy storage layer, and a dummy tunneling layer.
6. The device of claim 5 , wherein the dummy barrier layer comprises a high-k material.
7. The device of claim 5 , wherein the dummy barrier layer is a silicon oxide layer.
8. The device of claim 5 , wherein the dummy barrier layer is a SiO 2 —SiON—SiO 2 multi-layer stack.
9. The device of claim 5 , wherein the dummy storage layer comprises a polycrystalline silicon layer.
10. The device of claim 9 , wherein the dummy storage layer further comprises one or more films of silicon nitride, silicon oxynitride, and a combination of silicon oxide and silicon nitride.
11. The device of claim 5 , wherein the dummy tunneling layer comprises one or more films of silicon oxide, silicon nitride, and silicon oxynitride.
12. The device of claim 1 , wherein the alternating layer stack comprises:
at least 32 conductive/dielectric layer pairs stacked in a vertical direction, wherein each conductive/dielectric pair comprises a dielectric layer and a conductive layer.
13. The device of claim 12 , wherein:
the top selective gate cut structure extends into three top conductive/dielectric layer pairs of the alternating layer stack.
14. The device of claim 1 , wherein the top selective gate cut structure extends between two rows of channel structures.
15. The device of claim 14 , wherein each channel structure of the plurality of channel structures comprises:
an epitaxial layer on a bottom of a channel hole of the each channel structure;
a functional layer on a sidewall of the channel hole; and
a channel layer covering a sidewall of the functional layer and being in contact with the epitaxial layer.
16. The device of claim 15 , wherein each channel structure further comprises:
a dielectric filling structure covering a sidewall of the channel layer and filling the channel hole; and
a channel plug on a top portion of the channel hole.
17. The device of claim 15 , wherein the functional layer comprises:
a barrier layer on the sidewall of the channel hole configured to block an outflow of electronic charges;
a storage layer on a surface of the barrier layer configured to store electronic charges during operation of the 3D memory device; and
a tunneling layer on a surface of the storage layer configured to tunnel electronic charges.
18. The device of claim 1 , wherein the top selective gate cut structure comprises:
a dummy functional layer covering sidewalls and a bottom of a trench;
a dummy channel layer covering the dummy functional layer;
a dielectric filling wall; and
a dummy channel strip cover on a top portion of the trench.
19. The device of claim 18 , wherein the dummy functional layer comprises a dummy barrier layer, a dummy storage layer, and a dummy tunneling layer.
20. The device of claim 18 , wherein:
the functional layer and the dummy functional layer have a same material and are formed in a same process;
the channel layer and the dummy channel layer have a same material and are formed in a same process;
a dielectric filling structure and the dielectric filling wall have a same material and are formed in a same process; and
a channel plug and the dummy channel strip cover have a same material and are formed in a same process.