Methods for forming all tungsten contacts and lines
Novel low-resistivity tungsten film stack schemes and methods for depositing them are provided. The film stacks include a mixed tungsten/tungsten-containing compound (e.g., WC) layer as a base for deposition of tungsten nucleation and/or bulk layers. According to various embodiments, these tungsten rich layers may be used as barrier and/or adhesion layers in tungsten contact metallization and bitlines. Deposition of the tungsten-rich layers involves exposing the substrate to a halogen-free organometallic tungsten precursor. The mixed tungsten/tungsten carbide layer is a thin, low resistivity film with excellent adhesion and a good base for subsequent tungsten plug or line formation.
1. A method of forming an all-tungsten plug, comprising:
providing a substrate comprising a contact hole in a dielectric layer to a reactor, said contact hole exposing a conductor;
flowing a non-halogen organometallic tungsten precursor and a reducing agent into the reactor, wherein the non-halogen organometallic tungsten precursor and the reducing agent are different compounds;
exposing the substrate to the non-halogen organometallic tungsten precursor and the reducing agent to thereby deposit a tungsten-rich film directly on at least the exposed conductor;
exposing the substrate to a tungsten-containing precursor to deposit one or more tungsten layers on the tungsten-rich film; and
substantially filling the hole with tungsten to form the tungsten plug.
2. The method of claim 1 wherein the tungsten-rich film comprises a mixture of metallic tungsten and at least one tungsten compound.
3. The method of claim 1 wherein the tungsten-rich film comprises a mixture of metallic tungsten and tungsten carbide.
4. The method of claim 3 wherein the molecular ratio of metallic tungsten (W) to tungsten carbide (WC) ranges from about 2:1 to 10:1.
5. The method of claim 3 wherein the molecular ratio of metallic tungsten (W) to tungsten carbide (WC) ranges from about 2:1 to 4:1.
6. The method of claim 1 wherein the tungsten-rich film comprises at least about 60 atomic percent tungsten.
7. The method of claim 1 wherein the tungsten-rich film comprises no more than about 25% carbon.
8. The method of claim 1 wherein the thickness of the tungsten-rich film ranges from about 10 angstroms to 100 angstroms.
9. The method of claim 1 wherein exposing the substrate to a tungsten-containing precursor to deposit one or more tungsten layers on the tungsten-rich film comprises exposing the substrate to WF 6 .
10. The method of claim 1 wherein exposing the substrate to a tungsten-containing precursor to deposit one or more tungsten layers on the tungsten-rich layer comprises depositing a tungsten nucleation layer on the tungsten-rich film, and depositing a bulk tungsten film on the tungsten nucleation layer.
11. The method of claim 1 , further comprising after substantially filling the contact hole with tungsten, etching back the tungsten to form the tungsten plug.
12. The method of claim 1 wherein the non-halogen organometallic tungsten precursor comprises at least one of the group consisting of alkyl, alkenyl, alkynyl and phenyl groups.
13. The method of claim 1 wherein the conductor is a metallic conductor.
14. A method of forming an all-tungsten line, comprising:
providing a substrate having front and back surfaces and layer of dielectric material overlying the front surface with a trench in the layer of dielectric material to a reactor, said trench connecting different regions on the semiconductor substrate and having a trench bottom and sidewalls wherein the sidewalls are formed of the dielectric material;
flowing a non-halogen organometallic tungsten precursor and a reducing agent into the reactor, wherein the non-halogen organometallic tungsten precursor and the reducing agent are different compounds;
exposing the substrate to the non-halogen organometallic tungsten precursor and the reducing agent to thereby deposit a tungsten-rich film directly on at least the bottom and sidewalls of the trench;
exposing the substrate to a tungsten-containing precursor to deposit one or more tungsten layers on the tungsten-rich film; and
substantially filling the trench with tungsten to form an all-tungsten line configured to have current flow along its length said length being substantially parallel to the front surface.
15. The method of claim 14 wherein the tungsten-rich film comprises a mixture of metallic tungsten and at least one tungsten compound.
16. A method of claim 14 wherein the tungsten-rich film comprises a mixture of metallic tungsten and tungsten carbide.
17. The method of claim 16 wherein the molecular ratio of metallic tungsten (W) to tungsten carbide (WC) is between about 2:1 and 10:1.
18. The method of claim 16 wherein the molecular ratio of metallic tungsten (W) to tungsten carbide (WC) is between about 2:1 and 4:1.
19. The method of claim 14 wherein the tungsten-rich film comprises at least about 70 atomic percent tungsten.
20. The method of claim 14 wherein the tungsten-rich film comprises no more than about 25% carbon.
21. The method of claim 14 wherein the thickness of the tungsten-rich film ranges from about 10 angstroms to 100 angstroms.
22. The method of claim 14 wherein exposing the substrate to a tungsten-containing precursor to deposit one or more tungsten layers on the tungsten-rich film comprises exposing the substrate to WF 6 .
23. The method of claim 14 wherein exposing the substrate to a tungsten-containing precursor to deposit one or more tungsten layers on the tungsten-rich film comprises depositing a tungsten nucleation layer on the tungsten-rich film, and depositing a bulk tungsten film on the tungsten nucleation layer.
24. The method of claim 14 wherein the non-halogen organometallic tungsten precursor comprises at least one of the group consisting of alkyl, alkenyl, alkynyl and phenyl groups.
25. The method of claim 14 wherein the all-tungsten line is part of a wiring level of a partially fabricated integrated circuit.
26. A method of forming all-tungsten bitlines, comprising:
providing a substrate to a reactor;
flowing a non-halogen organometallic tungsten precursor and a reducing agent into the reactor, wherein the non-halogen organometallic tungsten precursor and the reducing agent are different compounds;
exposing the substrate to the non-halogen organometallic tungsten precursor and the reducing agent to thereby deposit a tungsten-rich film on at least a directly on a dielectric portion of the substrate;
exposing the substrate to a tungsten-containing precursor to deposit a tungsten bitline film directly on the tungsten-rich film; and
photopatterning and etching the tungsten bitline film to form the bitlines.
27. A method of forming an all tungsten plug or line, the method comprising:
providing in a reactor a substrate comprising a contact hole or trench in a dielectric layer, the contact hole exposing a conductor and the trench having a trench bottom and sidewalls, the sidewalls comprising an exposed dielectric surface;
flowing a non-halogen organometallic tungsten precursor and a reducing agent into the reactor, wherein the non-halogen organometallic tungsten precursor and the reducing agent are different compounds;
exposing the substrate to the non-halogen organometallic tungsten precursor and the reducing agent to thereby deposit a conformal and continuous tungsten-rich film directly on the conductor or trench bottom and sidewalls, wherein the tungsten-rich film comprises a mixture of metallic tungsten and a tungsten carbide;
exposing the substrate to a tungsten-containing precursor to deposit one or more tungsten layers on the tungsten-rich film; and
substantially filling the hole or trench with tungsten to form the tungsten plug or line.