Methods for removing metal oxides
Methods to remove metal oxides from substrate surfaces are described. Some embodiments of the disclosure utilize an aqueous alkaline solution to remove metal oxides from substrate surfaces using a wet method. Some embodiments of the disclosure are performed at atmospheric pressure and lower temperatures. Methods of forming self-aligned vias are also described.
1. A method comprising:
providing a substrate in a reaction chamber, the substrate having a dielectric substrate surface with at least one feature formed therein, the at least one feature extending a distance from the substrate surface into the substrate and having a sidewall and a bottom, the at least one feature having a first metal film comprising a first metal therein and a first metal oxide film on the first metal film, the first metal oxide film comprising the first metal, wherein the first metal film is partially oxidized to form the first metal oxide film on the first metal film; and
exposing the substrate to an aqueous alkaline solution to remove the first metal film and the first metal oxide film from the feature without affecting the substrate surface adjacent to the feature, the aqueous alkaline solution comprising one or more of NaOH and KOH and having a hydroxide concentration of less than or equal to about 0.1 M,
wherein no plasma is used and wherein the reaction chamber is not purged.
2. The method of claim 1 , wherein the first metal comprises tungsten.
3. The method of claim 1 , wherein the at least one feature further comprises a liner and the first metal oxide film is on the liner and exposure to the aqueous alkaline solution does not affect the liner.
4. The method of claim 3 , wherein the liner comprises one or more of SiN or SiCN.
5. The method of claim 3 , wherein the at least one feature further comprises a second metal film having a second metal below the liner.
6. The method of claim 5 , wherein the second metal is different from the first metal.
7. The method of claim 6 , wherein the second metal comprises one or more of copper, cobalt, and ruthenium.
8. The method of claim 1 , wherein the aqueous alkaline solution comprises a base with a pKb of less than or equal to about 5.
9. The method of claim 1 , wherein the substrate is exposed to the aqueous alkaline solution at atmospheric pressure.
10. The method of claim 1 , wherein the substrate is maintained at a temperature in a range of about 50° C. to about 250° C.
11. The method of claim 1 , wherein the at least one feature has an aspect ratio of greater than or equal to about 10:1.
12. The method of claim 1 , further comprising rinsing the substrate with an aqueous solution.
13. A method comprising:
providing a substrate in a reaction chamber, the substrate having a substrate surface with at least one feature formed therein, the at least one feature extending a distance from the substrate surface into the substrate and having a sidewall and bottom, the at least one feature having an aspect ratio greater than or equal to about 10:1, the at least one feature having a tungsten film therein and a tungsten oxide film on the tungsten film, wherein the tungsten film is partially oxidized to form the tungsten oxide film on the tungsten film;
exposing the substrate to an aqueous hydroxide solution to remove the tungsten film and the tungsten oxide film from the feature without affecting the substrate surface adjacent to the feature, the aqueous hydroxide solution comprising one or more of NaOH and KOH and having a hydroxide concentration of less than or equal to about 0.1 M; and
rinsing the substrate with a solution comprising water and isopropyl alcohol,
wherein no plasma is used and wherein the reaction chamber is not purged.
14. A method to provide a self-aligned via, the method comprising:
providing a substrate in a reaction chamber, the substrate having a plurality of first conductive lines between a plurality of first insulating layers which are substantially coplanar and extend along a first direction;
recessing portions of the first conductive lines;
depositing a liner on the recessed portions of the first conductive lines;
forming a first metal film on the liner;
partially oxidizing the first metal film to form pillars comprising an oxide of the first metal film;
depositing a second insulating layer around the pillars; and
removing the pillars to form vias in the second insulating layer by exposing the substrate to an aqueous alkaline solution to remove the pillars and the first metal film without affecting the first insulating layers, the liner or the second insulating layer, the aqueous alkaline solution comprising one or more of NaOH and KOH and having a hydroxide concentration of less than or equal to about 0.1 M,
wherein no plasma is used and wherein the reaction chamber is not purged.
15. The method of claim 14 , further comprising removing the liner after either the pillars are removed from the vias.
16. The method of claim 14 , further comprising:
depositing a third insulating layer in the vias and on the second insulating layer to form filled vias and an overburden of third insulating layer;
removing a portion of the overburden of the third insulating layer and the third insulating layer from the filled vias to form via openings;
depositing a second conductive material into the via opening; and
depositing a second conductive line on the second insulating layer and in contact with the second conductive material in the via opening, the second conductive line extending along a second direction on the second insulating layer, the second direction crossing the first direction at an angle in a range of about 30° to about 150°.