Tungsten nitride barrier layer deposition
Provided herein are methods of tungsten nitride (WN) deposition. Also provided are stacks for tungsten (W) contacts to silicon germanium (SiGe) layers and methods for forming them. The stacks include SiGe/tungsten silicide (WSi x )/WN/W layers, with WSi x providing an ohmic contact between the SiGe and WN layers. Also provided are methods for reducing fluorine (F) attack of underlying layers in deposition of W-containing films using tungsten hexafluoride (WF 6 ). Apparatuses to perform the methods are also provided.
1. A method comprising:
providing a feature formed in a dielectric layer and a silicon germanium (SiGe) layer on a substrate, wherein the feature comprises a SiGe surface;
exposing the SiGe surface to nitrogen radicals to treat the SiGe surface;
depositing a tungsten (W) layer on the treated SiGe surface; and
depositing a tungsten nitride (WN) layer conformal to the feature.
2. The method of claim 1 , further comprising filling the feature with tungsten (W).
3. The method of claim 1 , wherein nitrogen radicals are generated in an inductively-coupled plasma generated from nitrogen (N 2 ) gas.
4. The method of claim 1 , further comprising forming a nitride layer on the SiGe surface.
5. The method of claim 1 , wherein depositing the W layer on the treated SiGe surface comprises exposing the substrate to alternating pulses of tungsten hexafluoride (WF 6 ) and a reducing agent.
6. The method of claim 5 , wherein the reducing agent is silane (SiH 4 ).
7. The method of claim 5 , wherein the treated SiGe surface prevents diffusion of fluorine from the WF 6 into SiGe underlying the treated SiGe surface.
8. The method of claim 1 , wherein the W layer is between 5 Å and 30 Å thick.
9. The method of claim 1 , wherein depositing WN layer comprises exposing the feature to alternating pulses of tungsten hexafluoride (WF 6 ), a reducing agent, and a nitriding agent.
10. The method of claim 9 , wherein the reducing agent is diborane (B 2 H 6 ) and the nitriding agent is ammonia (NH 3 ).
11. The method of claim 9 , wherein the ratio of WF 6 to reducing agent molecules that the feature is exposed to is greater than 2:1.
12. The method of claim 11 , wherein the ratio is greater than 2.5:1.
13. The method of claim 1 , wherein all or a portion of the W layer is converted to a tungsten silicide layer during deposition of the W layer on the SiGe surface.
14. The method of claim 1 , wherein the WN layer includes halogen impurities.
15. The method of 14 , further comprising dehalogenating the WN layer.
16. The method of claim 15 , wherein dehalogenating the WN layer comprises exposing it to a plasma generated from hydrogen (H 2 ) and an inert gas.
17. The method of claim 1 , further comprising exposing the WN layer to a plasma generated from hydrogen (H 2 ).
18. The method of claim 1 , further comprising exposing the WN layer to a plasma generated from an inert gas.
19. The method of claim 1 , wherein the treated SiGe surface comprises a nitride layer on the SiGe surface.
20. The method of claim 1 , wherein all or a portion of the W layer is converted to a silicide during deposition of the W layer.