Methods of filling horizontally-extending openings of integrated assemblies

1. A method of forming an integrated structure, comprising:

forming an assembly to include a vertical stack of alternating first and second levels; the first levels being horizontally-extending insulative levels and comprising insulative material; the second levels comprising voids between the horizontally-extending insulative levels; the assembly including channel material structures extending through the stack; the voids having peripheral regions lined with a conductive seed material;

growing a first material along the conductive seed material to partially fill the voids;

etching the first material to remove some of the first material from within the voids; and

growing a second material over the first material to fill the voids.

2. The method of claim 1 wherein the first material is a same composition as the second material.

3. The method of claim 1 wherein the first and second materials are different compositions relative to one another.

4. The method of claim 1 wherein the first and second materials comprise one or more of tungsten, titanium, ruthenium, cobalt, nickel and molybdenum.

5. The method of claim 1 wherein the first and second materials comprise tungsten.

6. The method of claim 1 wherein the etching of the first material utilizes one or more of phosphoric acid, acetic acid and nitric acid.

7. The method of claim 6 wherein the etching of the first material is conducted at a temperature within a range of from about 60° C. to about 100° C.

8. The method of claim 1 wherein the etching of the first material utilizes a combination of phosphoric acid, acetic acid and nitric acid.

9. The method of claim 1 wherein the filled voids comprise wordline levels of a three-dimensional NAND memory array.