Atomic layer deposition of passivation layer

1 . A method for processing a substrate, the method comprising:

forming a passivation layer over sidewalls of a recess in a carbon-containing layer of the substrate by a cyclic passivation process comprising a plurality of cycles, the substrate comprising the carbon-containing layer over a dielectric layer, each of the plurality of cycles comprising,

exposing the substrate to a first gas comprising a refractory metal in the absence of a plasma, and

after exposing to the first gas, exposing the substrate to a second gas comprising oxygen or nitrogen; and

patterning the dielectric layer using the carbon-containing layer as an etch mask.

2 . The method of claim 1 , wherein the exposing to the second gas comprises exposing the substrate to a first plasma generated from the second gas.

3 . The method of claim 1 , further comprising, after the cyclic passivation process, exposing the substrate to a second plasma generated from a third gas comprising oxygen, sulfur, nitrogen, or hydrogen to extend the recess in the carbon-containing layer, the passivation layer covering the sidewalls during the exposing to the second plasma.

4 . The method of claim 1 , further comprising, before forming the passivation layer, forming the recess by performing an anisotropic plasma etch process with a patterned mask layer over the carbon-containing layer.

5 . The method of claim 4 , wherein the patterned mask layer comprises silicon nitride, silicon oxide (SiO 2 ), or silicon oxynitride (SiON).

6 . The method of claim 1 , wherein the carbon-containing layer comprises amorphous carbon.

7 . The method of claim 1 , wherein the refractory metal comprises tungsten, niobium, or molybdenum.

8 . The method of claim 1 , wherein the first gas comprises a halide of the refractory metal.

9 . The method of claim 1 , wherein the second gas comprises water (H 2 O) or ammonia (NH 3 ).

10 . A method for processing a substrate, the method comprising:

forming a carbon-containing layer over a dielectric layer of a substrate;

forming an initial recess in the carbon-containing layer by exposing the substrate to a first plasma, the initial recess comprising sidewalls;

forming a passivation layer over the sidewalls by

exposing the substrate to a metal precursor gas comprising a halide of a refractory metal, and

exposing the substrate to a second gas comprising oxygen or nitrogen; and

extending the initial recess in the carbon-containing layer by exposing the substrate to the first plasma, the passivation layer covering the sidewalls of the carbon-containing layer during the extending.

11 . The method of claim 10 , wherein the forming of the passivation layer further comprises repeating the exposing to the metal precursor gas and the exposing to the second gas to gradually grow the passivation layer.

12 . The method of claim 10 , wherein the forming of the passivation layer is performed in a plasma processing chamber having a plasma source, wherein the exposing to the metal precursor gas is performed without powering the plasma source, and wherein the exposing to the second gas comprises:

purging the plasma processing chamber with the second gas, the second gas further comprising hydrogen,

powering the plasma source to generate a second plasma from the second gas, and

exposing the substrate to the second plasma.

13 . The method of claim 10 , wherein the halide of the refractory metal comprises tungsten fluoride, niobium fluoride, niobium chloride, molybdenum fluoride, or molybdenum chloride.

14 . The method of claim 10 , further comprising repeating the forming of the passivation layer and the extending of the initial recess to expose a portion of the dielectric layer at the bottom of the extended initial recess.

15 . The method of claim 14 , further comprising, after the repeating, patterning the dielectric layer by an anisotropic plasma etch process using the carbon-containing layer as an etch mask.

16 . The method of claim 10 , further comprising after extending the initial recess to expose a portion of the dielectric layer, patterning the dielectric layer by an anisotropic plasma etch process using the carbon-containing layer as an etch mask.

17 . A method for processing a substrate, the method comprising:

forming a carbon-containing layer over a dielectric layer of a substrate;

forming an initial recess in the carbon-containing layer by exposing the substrate to a first plasma, the initial recess comprising sidewalls;

forming a passivation layer over the sidewalls by

exposing the substrate to a metal precursor gas comprising a halide of a refractory metal, and

exposing the substrate to a second gas comprising oxygen or nitrogen;

extending the initial recess by exposing the substrate to the first plasma, the passivation layer covering the sidewalls during the extending-extending;

repeating the forming of the passivation layer and the extending of the initial recess to expose a portion of the dielectric layer at a bottom of the extended initial recess; and

after the repeating, patterning the dielectric layer by an anisotropic plasma etch process using the carbon-containing layer as an etch mask.

18 . The method of claim 17 , wherein the dielectric layer comprises silicon oxide or silicon nitride.

19 . The method of claim 17 , wherein the initial recess is formed in dielectric layer comprises a stack of alternating layers of silicon oxide and silicon nitride.

20 . The method of claim 17 , wherein the carbon-containing layer comprises amorphous carbon, forming the initial recess comprises using a patterned hard mask layer comprising silicon as an etch mask.

21 . The method of claim 17 , wherein patterning the dielectric layer comprises forming a recess in the dielectric layer with an aspect ratio between 5 and 100.