Methods of forming tungsten structures

1. A method of forming a multilayer structure, the method comprising:

forming a recess in a dielectric level;

forming a seed layer comprising tungsten and silicon in the recess; and

forming a tungsten fill over the seed layer, wherein a majority of the tungsten of the tungsten fill has a grain size having a longest dimension of at least 20 nm.

2. The method of claim 1 , wherein an amount of the silicon in the seed layer is between about 4-28% by atomic weight of the seed layer.

3. The method of claim 1 , wherein tungsten of the seed layer comprises both alpha and beta phase tungsten.

4. The method of claim 3 , wherein the seed layer is about 10-60% beta phase tungsten by atomic weight.

5. The method of claim 1 , wherein the seed layer contacts both the dielectric level and the tungsten fill in the recess.

6. The method of claim 1 , wherein forming the seed layer comprises doping the tungsten with silicon to form a silicon-doped tungsten seed layer.

7. The method of claim 1 , wherein forming the seed layer comprises depositing silicon and tungsten simultaneously.

8. The method of claim 1 , wherein the majority of the tungsten in the tungsten fill is alpha phase tungsten and has a grain size between 30 and 50 nm.

9. The method of claim 8 , wherein forming the seed layer comprises depositing tungsten by physical vapor deposition (PVD).

10. The method of claim 1 , further comprising performing processing to deposit the tungsten fill at temperatures of 300° C. or greater, after deposition of the silicon-containing tungsten seed layer.

11. The method of claim 10 , wherein the tungsten fill is deposited by chemical vapor deposition (CVD).

12. A multilayer structure, comprising:

a first dielectric level;

a second dielectric level disposed on the first dielectric level, the second dielectric level comprising recesses formed therein, at least some of the recesses extending to the first dielectric level;

a seed layer comprising tungsten and silicon disposed in the recesses and contacting both the first dielectric and the second dielectric level in the recesses; and

a tungsten fill disposed on the seed layer and filling the recesses in which the seed layer is present, the majority of the tungsten in the tungsten fill having a grain size with a maximum dimension of at least about 20 nm.

13. The multilayer structure of claim 12 , wherein an amount of the silicon in the seed layer is between about 4-28% by atomic weight.

14. The multilayer structure of claim 13 , wherein the tungsten of the seed layer comprises both alpha and beta phase tungsten, the seed layer containing about 10-60% beta phase tungsten by atomic weight.

15. The multilayer structure of claim 13 , wherein the tungsten fill comprises at least about 40% alpha phase tungsten having a grain size with a maximum dimension between 30 nm and 50 nm.

16. The multilayer structure of claim 13 , wherein a resistivity of the seed layer is higher than that of the alpha phase tungsten and a resistivity of a combination of the seed layer and the tungsten fill is less than that of alpha phase tungsten without the silicon-doped tungsten seed layer deposited under similar processing conditions.

17. The multilayer structure of claim 13 , wherein a resistivity of the tungsten fill material is 2-4 f/sq for a recess of about 10-20 nm in width and between 50-100 nm in depth.

18. The multilayer structure of claim 13 , wherein the first dielectric level is a nitride, the second dielectric level is an oxide, and the recesses terminate at the nitride.

19. A memory device, comprising:

an oxide level comprising recesses;

a silicon-containing tungsten seed layer disposed in the recesses; and

a tungsten fill material disposed in the recesses on the silicon-containing tungsten seed layer, an upper surface of the tungsten fill material in the recesses planar with an upper surface of the oxide level outside the recesses, the silicon-containing tungsten seed layer disposed between the tungsten fill material and the oxide level, the majority of the tungsten fill material having a grain size of about 30-50 nm.

20. The memory device of claim 19 , wherein the recesses extend along a length of the memory device to form word lines or bit lines of the memory device, the recesses being between about 50-200 nm in depth and about 20 nm in width.

21. The memory device of claim 19 , wherein:

an amount of the silicon in the silicon-containing tungsten seed layer is between about 4-28% by atomic weight.

22. The memory device of claim 19 , wherein:

the silicon-containing tungsten film includes a mixture of alpha and beta phase tungsten, the silicon-doped tungsten film containing about 10-60% beta phase tungsten by atomic weight,

a majority of the tungsten fill material is alpha phase tungsten, and

a resistivity of the tungsten fill material is 2-4 Ω/sq for a recess of about 20 nm wide and between 50-100 nm in depth.

23. A method of forming a semiconductor device, comprising:

forming a seed layer comprising tungsten and silicon over a support surface of the semiconductor device; and

forming a tungsten structure over the doped tungsten-comprising seed layer, the tungsten structure forming a conductive line in which at least 50% of the tungsten is in alpha phase; and wherein at least 50% of the tungsten has a grain size with a maximum dimension of at least about 20 nm.

24. The method of claim 23 , wherein forming the seed layer comprises doping tungsten with silicon.

25. The method of claim 23 , wherein forming the seed layer comprises depositing an alloy comprising tungsten and silicon.

26. The method of claim 25 , wherein forming the seed layer comprises co-depositing silicon and tungsten by plasma vapor deposition.