Fluorine-free tungsten ALD for dielectric selectivity improvement
Methods of forming metallic tungsten films selectively on a conductive surface relative to a dielectric surface are described. A substrate is exposed to a first process condition to deposit a tungsten-containing film that is substrate free of tungsten metal. The tungsten-containing film is then converted to a metallic tungsten film by exposure to a second process condition.
1. A method comprising:
exposing a substrate surface with a structure formed thereon to a first process condition, the structure having a bottom and sidewall, the bottom of the structure comprising a conductive surface and the sidewall of the structure comprising a dielectric surface, the first process comprising a flow of fluorine-free tungsten precursor and a flow of a first reducing agent to form a tungsten-containing film selectively on the conductive surface relative to the dielectric surface on the substrate surface, the tungsten-containing film being substantially free of tungsten metal, the first reducing agent having a flow rate in the range of 5% to 70% of a flow rate of the fluorine-free tungsten precursor;
exposing the tungsten-containing film to a second process condition comprising a flow of a second reducing agent to reduce the tungsten-containing film on the substrate surface to a metallic tungsten film; and
filling the structure with metallic tungsten using a tungsten hexafluoride based bulk tungsten deposition.
2. The method of claim 1 , wherein the fluorine-free tungsten precursor consists essentially of tungsten halide.
3. The method of claim 1 , wherein the fluorine-free tungsten precursor comprises one or more of tungsten pentachloride (WCl 5 ) or tungsten hexachloride (WCl 6 ).
4. The method of claim 1 , wherein the first reducing agent comprises one or more of hydrogen (H 2 ), silane (SiH 4 ), disilane (Si 2 H 6 ), trisilane (Si 3 H 8 ), tetrasilane (Si 4 H 10 ) or ammonia (NH 3 ).
5. The method of claim 1 , wherein the second reducing agent comprises one or more of hydrogen (H 2 ), silane (SiH 4 ), disilane (Si 2 H 6 ), trisilane (Si 3 H 8 ), tetrasilane (Si 4 H 10 ) or ammonia (NH 3 ).
6. The method of claim 1 , wherein the first reducing agent and the second reducing agent comprise the same reactive species.
7. The method of claim 1 , wherein the first reducing agent has a flow rate in the range of 50 to 500 sccm.
8. The method of claim 1 , wherein the dielectric surface comprises one or more of silicon nitride, silicon oxide.
9. The method of claim 1 , wherein the conductive surface comprises one or more of titanium nitride, titanium aluminum, aluminum or titanium.
10. The method of claim 1 , further comprising purging between the first process condition and the second process condition.
11. The method of claim 1 , wherein the metallic tungsten film deposits at a rate greater than or equal to twice a deposition rate of a substantially similar process without the first reducing agent in the first process condition.
12. The method of claim 1 , wherein the substrate surface is maintained at a temperature in the range of 400° C. to 550° C. during the first process condition and the second process condition.
13. The method of claim 1 , further comprising forming a nucleation layer on the substrate surface prior to exposure to the first process condition, and the substrate surface is not exposed to air between formation of the nucleation layer and the first process condition.