Three-dimensional memory device and method

1. A method of forming a three-dimensional (3D) memory device, the method comprising:

forming a layer stack over a substrate, the layer stack comprising alternating layers of a first dielectric material and a second dielectric material;

forming first trenches extending through the layer stack, the first trenches exposing first sidewalls of the first dielectric material and second sidewalls of the second dielectric material;

recessing the second sidewalls of the second dielectric material from the first sidewalls of the first dielectric material to form first recesses;

filling the first recesses with a first electrically conductive material to form word lines (WLs);

lining sidewalls and bottoms of the first trenches with a ferroelectric material after filling the first recesses;

filling the first trenches with a third dielectric material after the lining;

forming a first bit line (BL) and a first source line (SL) in the third dielectric material in one of the first trenches, wherein the first BL and the first SL extend vertically through the third dielectric material from a lower surface of the third dielectric material facing the substrate to an upper surface of the third dielectric material distal from the substrate;

removing portions of the third dielectric material disposed between the first BL and the first SL to form a first opening in the third dielectric material;

forming a channel material along sidewalls of the first opening; and

filling the first opening with a fourth dielectric material.

2. The method of claim 1 , wherein filling the first recesses comprises:

forming a seed layer over exposed surfaces of the first dielectric material and the second dielectric material;

forming the first electrically conductive material over the seed layer, the first electrically conductive material filling the first recesses; and

performing an anisotropic etching process to remove portions of the seed layer and portions of the first electrically conductive material that are disposed outside the first recesses.

3. The method of claim 1 , further comprising, after filling the first trenches and before forming the first BL and the first SL:

forming second trenches extending through the layer stack, the second trenches being interleaved with the first trenches;

recessing the second dielectric material exposed by the second trenches to form second recesses;

filling the second recesses with the first electrically conductive material to form additional WLs;

forming the ferroelectric material along sidewalls and bottoms of the second trenches after filling the second recesses; and

filling the second trenches with the third dielectric material after forming the ferroelectric material along the sidewalls and the bottoms of the second trenches.

4. The method of claim 3 , wherein after filling the second recesses, there is no second dielectric material disposed laterally between the WLs and the additional WLs.

5. The method of claim 3 , further comprising forming a second BL and a second SL in the third dielectric material in one of the second trenches, wherein in a top view, the first BL and the first SL are staggered with respect to the second BL and the second SL.

6. The method of claim 1 , wherein forming the first BL and first SL comprises:

forming a second opening in the third dielectric material at a location corresponding to the first BL, the second opening extending vertically through the third dielectric material;

forming a third opening in the third dielectric material at a location corresponding to the first SL, the third opening extending vertically through the third dielectric material; and

filling the second opening and the third opening with a second electrically conductive material.

7. The method of claim 1 , wherein the first opening exposes a sidewall of the first SL, a sidewall of the first BL, and sidewalls of the ferroelectric material.

8. The method of claim 1 , wherein after filling the first opening, the channel material encircles the fourth dielectric material in a top view.

9. The method of claim 1 , wherein forming the channel material comprises:

forming the channel material along the sidewalls of the first opening and along a bottom of the first opening; and

performing an anisotropic etching process to remove portions of the channel material from the bottom of the first opening.

10. The method of claim 9 , further comprising, after forming the channel material and before filling the first opening, forming a conformal oxide layer in the first opening over the channel material, wherein performing the anisotropic etching process further removes portions of the conformal oxide layer from the bottom of the first opening.

11. The method of claim 9 , wherein performing the anisotropic etching process further removes portions of the ferroelectric material from the bottom of the first opening.

12. A method of forming a three-dimensional (3D) memory device, the method comprising:

forming a layer stack over a substrate, the layer stack comprising alternating layers of a first dielectric material and a second dielectric material;

forming trenches extending through the layer stack;

replacing the second dielectric material with an electrically conductive material to form word lines (WLs);

lining sidewalls and bottoms of the trenches with a ferroelectric material;

filling the trenches with a third dielectric material;

forming bit lines (BLs) and source lines (SLs) extending vertically through the third dielectric material;

removing portions of the third dielectric material to form openings in the third dielectric material between the BLs and the SLs;

forming a channel material along sidewalls of the openings; and

filling the openings with a fourth dielectric material.

13. The method of claim 12 , wherein forming BLs and SLs comprises:

forming recesses extending vertically through the third dielectric material, wherein each of the recesses exposes a first sidewall of the ferroelectric material and a second sidewall of the ferroelectric material facing the first sidewall; and

filling the recesses with one or more electrically conductive materials.

14. The method of claim 12 , wherein bottoms of the openings are free of the channel material.

15. The method of claim 12 , further comprising, after forming the channel material and before filling the openings:

forming an oxide layer conformally in the openings; and

after forming the oxide layer, performing an anisotropic etching process to remove the oxide layer from the bottoms of the openings.

16. The method of claim 15 , wherein performing the anisotropic etching process further removes portions of the ferroelectric material disposed at the bottoms of the openings.

17. A method of forming a three-dimensional (3D) memory device, the method comprising:

forming a layer stack over a substrate, the layer stack comprising alternating layers of a first dielectric material and a second dielectric material;

forming a trench extending through the layer stack;

replacing the second dielectric material of the layer stack with conductive features to form word lines (WLs);

conformally forming a ferroelectric material along sidewalls and a bottom of the trench;

filling the trench with a third dielectric material;

forming a bit line (BL) and source line (SL) extending vertically through the third dielectric material;

forming an opening in the third dielectric material between the BL and the SL;

lining sidewalls of the opening with a channel material; and

filling the openings with a fourth dielectric material.

18. The method of claim 17 , wherein replacing the second dielectric material comprises:

removing portions of the second dielectric material exposed by the trench to form recesses;

forming a seed layer in the recesses; and

forming a conductive material in the recesses on the seed layer.

19. The method of claim 17 , wherein the BL and SL extend through the ferroelectric material.

20. The method of claim 17 , wherein the fourth dielectric material extends through the ferroelectric material.