Method and apparatus for remote plasma treatment for reducing metal oxides on a metal seed layer
Method and apparatus for reducing metal oxide surfaces to modified metal surfaces are disclosed. By exposing a metal oxide surface to a remote plasma, the metal oxide surface on a substrate can be reduced to pure metal and the metal reflowed. A remote plasma apparatus can treat the metal oxide surface as well as cool, load/unload, and move the substrate within a single standalone apparatus. The remote plasma apparatus includes a processing chamber and a controller configured to provide a substrate having a metal seed layer in a processing chamber, form a remote plasma of a reducing gas species where the remote plasma includes radicals, ions, and/or ultraviolet (UV) radiation from the reducing gas species, and expose a metal seed layer of the substrate to the remote plasma to reduce oxide of the metal seed layer to metal and to reflow the metal.
1. A remote plasma apparatus for treating a substrate with a metal seed layer, the remote plasma apparatus comprising:
a processing chamber;
a substrate support for holding the substrate in the processing chamber, wherein a portion of the metal seed layer of the substrate has been converted to oxide of the metal;
one or more cooling gas inlets above the substrate support in the processing chamber;
a remote plasma source over the substrate support;
a reducing gas inlet connected to the remote plasma source;
a showerhead between the remote plasma source and the substrate support, wherein the one or more cooling gas inlets are positioned to provide cooling gas through the showerhead and/or provide cooling gas from an area peripheral to the substrate between the showerhead and the substrate support; and
a controller configured with instructions for performing the following operations:
forming a remote plasma of a reducing gas species in the remote plasma source, wherein the remote plasma comprises one or more of: radicals of the reducing gas species, ions of the reducing gas species, and ultraviolet (UV) radiation generated from excitation of the reducing gas species;
exposing the metal seed layer of the substrate to the remote plasma in the processing chamber under conditions that reduce the oxide of the metal and reflows the metal in the metal seed layer; and
flowing a cooling gas in the processing chamber from the one or more cooling gas inlets to cool the substrate after completion of exposing the metal seed layer to the remote plasma, the remote plasma apparatus being configured to cool the substrate to a temperature of about 30° C. in a span between about 40 seconds and about 100 seconds when flowing the cooling gas after completion of exposing the metal seed layer to the remote plasma.
2. The apparatus of claim 1 , wherein the wavelength of the UV radiation generated from excitation of the reducing gas species is between about 100 nm and about 700 nm.
3. The apparatus of claim 1 , wherein the remote plasma comprises radicals of the reducing gas species, ions of the reducing gas species, and UV radiation generated from excitation of the reducing gas species.
4. The apparatus of claim 3 , wherein the remote plasma further comprises neutral molecules of the reducing gas species, and wherein exposing the metal seed layer to the remote plasma further comprises exposing the metal seed layer to neutral molecules of the reducing gas species.
5. The apparatus of claim 1 , wherein the showerhead comprises a plurality of holes, the number of holes in the showerhead being between about 100 and about 900 holes.
6. The apparatus of claim 1 , wherein the showerhead comprises a plurality of holes, the average diameter of the holes being between about 0.05 and about 0.5 inches.
7. The apparatus of claim 1 , wherein the showerhead has a thickness between about 0.25 and about 3.0 inches.
8. The apparatus of claim 1 , wherein exposing the metal seed layer to the remote plasma reduces a surface roughness of the metal seed layer.
9. The apparatus of claim 1 , wherein the remote plasma apparatus is part of an electroplating or electroless plating system.
10. The apparatus of claim 9 , wherein the controller is further configured with instructions for transferring the substrate to a plating bath containing a plating solution in the electroplating or electroless plating system from the remote plasma apparatus.
11. The apparatus of claim 1 , further comprising one or more movable members in the processing chamber configured to move the substrate away from the substrate support to positions between the showerhead and the substrate support, wherein the controller is further configured with instructions for moving the substrate towards the substrate support via the one or more movable members before exposing the substrate to the cooling gas.
12. The apparatus of claim 1 , wherein the controller is further configured with instructions for heating the substrate support to a processing temperature during the operations of forming the remote plasma and exposing the metal seed layer to the remote plasma, wherein the processing temperature is between about 0° C. and about 400° C.
13. The apparatus of claim 1 , wherein the metal seed layer includes at least one of copper, cobalt, ruthenium, palladium, rhodium, iridium, osmium, nickel, gold, silver, aluminum, and tungsten.
14. The apparatus of claim 1 , further comprising:
a UV source, wherein the controller is further configured with instructions for exposing reducing gas species to UV radiation from the UV source to form radicals of the reducing gas species.
15. The apparatus of claim 1 , further comprising:
a power source configured to bias the substrate support, wherein the controller is further configured with instructions for applying a charged bias on the substrate support.
16. The apparatus of claim 1 , wherein the controller is further configured with instructions for maintaining a temperature of the showerhead at a temperature below about 30° C. during exposure to the remote plasma and during flowing the cooling gas.
17. The apparatus of claim 16 , further comprising one or more movable members in the processing chamber configured to move the substrate away from the substrate support to positions between the showerhead and the substrate support, wherein the controller is further configured with instructions for moving the substrate towards the showerhead to further cool the substrate during flowing the cooling gas.
18. The apparatus of claim 1 , wherein the one or more cooling gas inlets are configured to flow the cooling gas in a direction substantially perpendicular to the substrate to cool the substrate.
19. A remote plasma apparatus comprising:
a processing chamber;
a substrate support for holding a substrate with a metal seed layer in the processing chamber, wherein a portion of the metal seed layer of the substrate has been converted to oxide of the metal;
a remote plasma source over the substrate support;
a reducing gas inlet connected to the remote plasma source;
a showerhead between the remote plasma source and the substrate support;
one or more movable members in the processing chamber configured to move the substrate away from the substrate support to positions between the showerhead and the substrate support; and
a controller configured with instructions for performing the following operations:
forming a remote plasma of a reducing gas species in the remote plasma source, wherein the remote plasma comprises one or more of: radicals of the reducing gas species, ions of the reducing gas species, and ultraviolet (UV) radiation generated from excitation of the reducing gas species;
exposing the metal seed layer of the substrate to the remote plasma in the processing chamber under conditions that reduce the oxide of the metal and reflows the metal in the metal seed layer; and
moving the substrate away from the substrate support and towards the showerhead to position the substrate closer to the showerhead during exposure to the remote plasma, wherein the showerhead is actively cooled to a temperature below about 30° C. during exposure to the remote plasma so that a temperature of the substrate can be lower when closer to the actively cooled showerhead than when further from the actively cooled showerhead.