Patterning methods for semiconductor devices

1. A method comprising:

forming a first mask layer over an underlying layer;

patterning the first mask layer to form a first opening;

forming a non-conformal film over the first mask layer, wherein a first thickness of the non-conformal film formed on a top surface of the first mask layer is greater than a second thickness of the non-conformal film formed on a sidewall surface of the first mask layer;

performing a descum process, wherein the descum process removes a portion of the non-conformal film within the first opening and leaves portions of the non-conformal film on the top surface and sidewall surface of the first mask layer, wherein after performing the descum process, a third thickness of the non-conformal film remaining on the top surface of the first mask layer is greater than a fourth thickness of the non-conformal film remaining on the sidewall surface of the first mask layer; and

etching the underlying layer using the patterned first mask layer and remaining portions of the non-conformal film as an etching mask.

2. The method of claim 1 , wherein patterning the first mask layer comprises patterning the first mask layer using an extreme ultraviolet (EUV) photolithography process.

3. The method of claim 1 , wherein forming the non-conformal film comprises forming the non-conformal film on a bottom surface of the first opening.

4. The method of claim 3 , wherein the descum process etches portions of the underlying layer.

5. The method of claim 3 , wherein the first thickness is greater than a third thickness of the non-conformal film formed on the bottom surface of the first opening.

6. The method of claim 1 , wherein the first thickness is between about 5 nm and about 10 nm, and wherein the second thickness is between about 1 nm and about 3 nm.

7. The method of claim 1 , wherein forming the non-conformal film comprises depositing the non-conformal film using a Plasma-Enhanced Atomic Layer Deposition (PEALD) process.

8. The method of claim 6 , wherein bis(diethylamino)silane is used as a precursor during the PEALD process.

9. The method of claim 1 , wherein the non-conformal film comprises SiCN.

10. The method of claim 1 , wherein the first mask layer is the top layer of a tri-layer photoresist.

11. The method of claim 1 , wherein the descum process comprises an ashing process.

12. A method, comprising:

forming a tri-layer structure over a substrate, the tri-layer structure comprising an upper layer, a middle layer, and a bottom layer;

patterning the upper layer to form a first mask pattern, the first mask pattern comprising a first opening;

depositing a protective layer extending over a top surface of the first mask pattern to a top surface of the middle layer within the first opening, wherein a first portion of the protective layer over the top surface of the first mask pattern is thicker than a second portion of the protective layer over the top surface of the middle layer within the first opening;

performing a descum process, wherein the descum process removes the second portion of the protective layer;

etching the middle layer using the first mask pattern and remaining portions of the protective layer as an etching mask to form a second mask pattern; and

etching the bottom layer using the second mask pattern as an etching mask to form a third mask pattern, wherein etching the bottom layer removes the remaining portions of the protective layer and the patterned upper layer.

13. The method of claim 12 , wherein the ratio of the thickness of the first portion of the protective layer to the thickness of the second portion of the protective layer is between 3:1 and 5:1.

14. The method of claim 12 , wherein depositing the protective layer comprises:

placing the substrate in a deposition chamber; and

performing one or more deposition cycles, each of the one or more deposition cycles comprising:

flowing one or more precursor materials into the deposition chamber;

purging the deposition chamber of precursor materials by flowing one or more purging gases into the deposition chamber;

igniting a plasma within the deposition chamber; and

purging the deposition chamber by flowing one or more purging gases into the deposition chamber.

15. The method of claim 12 , further comprising etching a second opening in the substrate using the third mask pattern as an etching mask.

16. The method of claim 15 , further comprising depositing a conductive material in the second opening to form a conductive line in the substrate.

17. A method, comprising:

forming an anti-reflective coating over a target layer;

forming a mask layer over the anti-reflective coating;

forming a dielectric layer over the mask layer;

forming a tri-layer masking layer over the dielectric layer, the tri-layer masking layer comprising a bottom layer over the dielectric layer, a middle layer over the bottom layer, and an upper layer over the middle layer;

patterning a trench in the upper layer;

forming a non-conformal film over the trench, wherein portions of the non-conformal film adjacent the trench are thicker than portions of the non-conformal film within the trench;

removing residue within the trench, wherein removing residue within the trench partially removes the middle layer;

after removing residue, etching the middle layer to extend the trench into the middle layer; and

etching the bottom layer to extend the trench into the bottom layer, wherein etching the bottom layer removes remaining portions of the non-conformal film and the upper layer.

18. The method of claim 17 , wherein portions of the non-conformal film adjacent the trench are about three times thicker than portions of the non-conformal film within the trench.

19. The method of claim 17 , wherein removing residue within the trench comprises a plasma process.

20. The method of claim 17 further comprising:

etching the dielectric layer to extend the trench into the dielectric layer;

removing remaining portions of the bottom layer;

etching the mask layer to extend the trench into the mask layer;

removing remaining portions of the dielectric layer;

etching the anti-reflective coating and the target layer to extend the trench into anti-reflective coating and the target layer; and

removing remaining portions of the mask layer.