Methods of improving tungsten contact resistance in small critical dimension features
Methods of filling features with low-resistivity tungsten layers having good fill without use of a nucleation layer are provided. In certain embodiments, the methods involve an optional treatment process prior to chemical vapor deposition of tungsten in the presence of a high partial pressure of hydrogen. According to various embodiments, the treatment process can involve a soaking step or a plasma treatment step. The resulting tungsten layer reduces overall contact resistance in advanced tungsten technology due to elimination of the conventional tungsten nucleation layer.
1. A method of filling a recessed feature on a substrate, the method comprising:
prior to depositing any tungsten in the feature, treating a surface of the feature with a non-nitrogen-containing chemistry; and
without depositing a nucleation layer, filling the feature with a tungsten film in a chemical vapor deposition (CVD) process by directly exposing the treated surface to a tungsten-containing precursor and hydrogen,
wherein the partial pressure of hydrogen is at least about 40 Torr during the CVD process.
2. The method in claim 1 , wherein the width of the feature is less than about 50 nm.
3. The method in claim 1 , wherein the feature surface comprises tungsten.
4. The method in claim 1 , wherein the feature surface comprises tungsten nitride.
5. The method in claim 1 , wherein the feature surface comprises titanium nitride.
6. The method in claim 1 , wherein the partial pressure of hydrogen is at least about 60 Torr during the CVD process.
7. The method in claim 1 , wherein the partial pressure of hydrogen is at least about 80 Torr during the CVD process.
8. The method in claim 1 , wherein treating the surface of the feature comprises soaking the substrate in a reducing agent.
9. The method in claim 8 , wherein the reducing agent is a borane, a silane, or a germane.
10. The method in claim 1 , wherein treating the surface of the feature comprises exposing the substrate to an inert gas-containing plasma.
11. The method in claim 10 , wherein the inert gas-containing plasma comprises argon and hydrogen species.
12. The method in claim 10 , wherein the substrate is kept under vacuum between treating the surface of the feature and filling the feature with a tungsten film in the CVD process.
13. A method of filling a recessed feature on a substrate, the method comprising:
prior to depositing any tungsten in the feature,
exposing a surface of the feature to a non-nitrogen inert gas-containing plasma; and
without depositing a nucleation layer, filling the feature with tungsten in a chemical vapor deposition (CVD) process by directly exposing the treated surface to a tungsten-containing precursor and a reducing agent in a CVD chamber.
14. The method in claim 13 , wherein the substrate comprises at least one of tungsten, tungsten nitride and titanium nitride.
15. The method in claim 13 , wherein the substrate is kept under vacuum between the plasma treatment and the CVD process.
16. The method in claim 13 , wherein exposing the surface of the feature to an inert gas-containing plasma occurs in a treatment chamber separate from the CVD chamber.
17. The method in claim 13 further comprising,
prior to the plasma treatment,
depositing a liner layer in the feature in a liner layer deposition chamber,
wherein exposing the surface of the feature to an inert gas-containing plasma occurs in the liner layer deposition chamber; and
transferring the substrate to the CVD chamber.
18. A method of filling a recessed feature on a substrate, the method comprising:
prior to depositing any tungsten in the feature, treating a surface of the feature with a non-nitrogen-containing chemistry; and
filling the feature with a tungsten film by directly exposing the treated surface to a tungsten-containing precursor and hydrogen in a chemical vapor deposition (CVD) process,
wherein the partial pressure of hydrogen is at least about 40 Torr during the CVD process, and
wherein hydrogen is the predominant reducing agent during the CVD process.
19. The method in claim 18 , wherein the partial pressure of hydrogen is at least about 60 Torr during the CVD process.