Tungsten feature fill with nucleation inhibition
Described herein are methods of filling features with tungsten, and related systems and apparatus, involving inhibition of tungsten nucleation. In some embodiments, the methods involve selective inhibition along a feature profile. Methods of selectively inhibiting tungsten nucleation can include exposing the feature to a direct or remote plasma. In certain embodiments, the substrate can be biased during selective inhibition. Process parameters including bias power, exposure time, plasma power, process pressure and plasma chemistry can be used to tune the inhibition profile. The methods described herein can be used to fill vertical features, such as in tungsten vias, and horizontal features, such as vertical NAND (VNAND) wordlines. The methods may be used for both conformal fill and bottom-up/inside-out fill. Examples of applications include logic and memory contact fill, DRAM buried wordline fill, vertically integrated memory gate/wordline fill, and 3-D integration using through-silicon vias.
1. A method comprising:
providing a substrate including a feature having a feature opening, a closed end, and a feature interior,
selectively inhibiting tungsten nucleation in the feature such that there is a differential inhibition profile along a feature axis wherein the differential inhibition profile is such that the inhibition at the closed end feature surface is less than at the feature opening; and
selectively depositing tungsten in the feature in accordance with the differential inhibition profile.
2. The method of claim 1 , wherein selectively inhibiting tungsten nucleation in the feature comprises exposing the feature to a direct plasma while applying a bias to the substrate.
3. The method of claim 2 , wherein the direct plasma contains one or more of nitrogen, hydrogen, oxygen and carbon activated species.
4. The method of claim 2 , wherein the direct plasma is nitrogen-based and/or hydrogen-based.
5. The method of claim 1 , wherein selectively inhibiting tungsten nucleation in the feature comprises exposing the feature to a remotely-generated plasma.
6. The method of claim 5 , wherein the remotely-generated plasma is nitrogen-based and/or hydrogen-based.
7. The method of claim 1 , further comprising depositing a tungsten layer in the feature prior to selective inhibition.
8. The method of claim 7 , wherein the tungsten layer is deposited by a pulsed nucleation layer (PNL) process.
9. The method of claim 7 , wherein the tungsten layer is conformally deposited in the feature.
10. The method of claim 1 , wherein selectively depositing tungsten comprises a chemical vapor deposition (CVD) process.
11. The method of claim 1 , further comprising, after selectively depositing tungsten in the feature, depositing tungsten in the feature to complete feature fill.
12. The method of claim 1 , further comprising, after selectively depositing tungsten in the feature, non-selectively depositing tungsten in the feature.
13. The method of claim 12 , wherein transitioning from selective to non-selective deposition comprises allowing a CVD process to continue without deposition of an intervening tungsten nucleation layer.
14. The method of claim 12 , wherein transitioning from selective to non-selective deposition comprising deposition of a tungsten nucleation layer on the selectively deposited tungsten.
15. The method of claim 1 , wherein selectively inhibiting tungsten nucleation comprises treating a tungsten surface of the feature.
16. The method of claim 1 , wherein selectively inhibiting tungsten nucleation comprises treating a metal nitride surface of the feature.
17. The method of claim 1 , wherein selective inhibition is performed without etching material in the feature.
18. The method of claim 1 , wherein the feature fill is performed without etching material in the feature.
19. The method of claim 1 , wherein the feature is part of a 3-D structure.
20. The method of claim 1 , further comprising repeating a cycle of selective inhibition and selective deposition one or more times to fill the feature.
21. The method of claim 1 , wherein at least a constriction in the feature is selectively inhibited.
22. The method of claim 1 , wherein selectively inhibiting tungsten nucleation in the feature comprises passivating a feature surface without forming a compound material.
23. The method of claim 1 , wherein selectively inhibiting tungsten nucleation in the feature comprises forming a tungsten compound material.