Metal-containing passivation for high aspect ratio etch
Various embodiments herein relate to methods, apparatus, and systems for etching a feature in a substrate. Typically the feature is etched in a dielectric-containing stack. The etching process involves cyclically etching the feature and depositing a protective film on sidewalls of the partially etched feature. These stages are repeated until the feature reaches its final depth. The protective film may have a particular composition, for example including at least one of a tungsten carbonitride, a tungsten sulfide, tin, a tin-containing compound, molybdenum, a molybdenum-containing compound, a ruthenium carbonitride, a ruthenium sulfide, an aluminum carbonitride, an aluminum sulfide, zirconium, and a zirconium-containing compound. A number of optional steps may be taken including, for example, doping the mask layer, pre-treating the substrate prior to deposition, removing the protective film from the sidewalls, and oxidizing any remaining protective film.
1. A method of forming an etched feature in a dielectric-containing stack on a substrate, the method comprising:
(a) partially etching the feature in the dielectric-containing stack by exposing the substrate to a first plasma comprising an etching reactant;
(b) after (a), depositing a protective film on sidewalls of the feature, the protective film comprising at least one of a tungsten carbonitride, a tungsten sulfide, tin, a tin-containing compound, molybdenum, a molybdenum-containing compound, a ruthenium sulfide, an aluminum sulfide, zirconium, and a zirconium-containing compound, wherein the protective film is not deposited on bottoms of the etch features; and
(c) repeating (a)-(b) until the feature is etched to a final depth, wherein the protective film deposited in (b) substantially prevents lateral etch of the feature during (a), and wherein the feature has an aspect ratio of about 5 or greater at its final depth.
2. The method of claim 1 , wherein the protective film comprises tungsten carbonitride, tungsten oxide, or tungsten sulfide.
3. The method of claim 2 , wherein the protective film comprises tungsten carbonitride.
4. The method of claim 1 , wherein the protective film comprises tin, tin oxide, tin nitride, tin carbide, tin carbonitride, or tin sulfide.
5. The method of claim 4 , wherein the protective film comprises tin oxide.
6. The method of claim 1 , wherein the protective film comprises molybdenum, molybdenum oxide, molybdenum carbide, molybdenum nitride, molybdenum carbonitride, or molybdenum sulfide.
7. The method of claim 1 , wherein the protective film comprises ruthenium sulfide.
8. The method of claim 1 , wherein the protective film comprises aluminum sulfide.
9. The method of claim 1 , wherein the protective film comprises zirconium, zirconium oxide, zirconium carbide, zirconium nitride, zirconium carbonitride, or zirconium sulfide.
10. The method of claim 1 , wherein (b) comprises depositing the protective film through an atomic layer deposition reaction comprising:
(i) exposing the substrate to a first deposition reactant and allowing the first deposition reactant to adsorb onto the sidewalls of the feature; and
(ii) after (i), exposing the substrate to a second deposition reactant and reacting the first and second deposition reactants in a surface reaction, thereby forming the protective film on the sidewalls of the feature.
11. The method of claim 1 , wherein (b) comprises depositing the protective film through a chemical vapor deposition reaction comprising exposing the substrate to a first deposition reactant and a second deposition reactant simultaneously.
12. The method of claim 1 , further comprising doping a mask layer on the dielectric-containing stack prior to (a).
13. The method of claim 1 , wherein (a) results in formation of a fluorocarbon-based coating on the sidewalls of the feature, the method further comprising after (a) and before (b), pre-treating the substrate to thereby remove or alter the fluorocarbon-based coating, and wherein pre-treating the substrate comprises exposing the substrate to plasma generated from either (i) a gas comprising N 2 and H 2 , or (ii) a gas comprising O 2 and inert gas.
14. The method of claim 13 , wherein the protective film comprises tungsten carbonitride.
15. The method of claim 1 , wherein (a) results in formation of a fluorocarbon-based coating on the sidewalls of the feature, wherein the protective film comprises tin oxide, and wherein the tin oxide protective film is deposited in (b) directly on the fluorocarbon-based coating formed in (a).
16. The method of claim 1 , further comprising removing the protective film from the sidewalls after the feature is fully etched.
17. The method of claim 1 , wherein the protective film comprises tungsten carbonitride and is removed by exposing the substrate to H 2 O 2 , SCl, or a plasma generated from a gas comprising Cl 2 O 2 .
18. The method of claim 1 , further comprising exposing the substrate to an oxidizing gas or plasma after the feature is fully etched to thereby oxidize any remaining protective film on the sidewalls of the feature forming metal oxides.
19. The method of claim 1 , wherein (a) results in formation of a fluorocarbon-based coating on the sidewalls of the feature, the method further comprising after (a) and before (b), pre-treating the substrate to thereby remove the fluorocarbon-based coating.
20. A method of forming an etched feature in a dielectric-containing stack on a substrate, the method comprising:
(a) partially etching the feature in the dielectric-containing stack by exposing the substrate to a first plasma comprising an etching reactant;
(b) after (a), depositing a protective film on sidewalls of the feature, the protective film comprising at least one of a tungsten carbonitride, a tungsten sulfide, tin, a tin-containing compound, molybdenum, a molybdenum-containing compound, a ruthenium sulfide, an aluminum sulfide, zirconium, and a zirconium-containing compound, wherein the protective film comprises a metal sulfide; and
(c) repeating (a)-(b) until the feature is etched to a final depth, wherein the protective film deposited in (b) substantially prevents lateral etch of the feature during (a), and wherein the feature has an aspect ratio of about 5 or greater at its final depth.