Reactive ion etching assisted lift-off processes for fabricating thick metallization patterns with tight pitch
Lift-off methods for fabricating metal line patterns on a substrate are provided. For example, a method to fabricate a device includes forming a sacrificial layer on a substrate and forming a photoresist mask over the sacrificial layer, isotropically etching a portion of the sacrificial layer exposed through an opening of the photoresist mask to form an undercut region in the sacrificial layer below the photoresist mask, wherein the undercut region defines an overhang structure, and anisotropically etching a portion of the sacrificial layer exposed through the opening of the photoresist mask to form an opening through the sacrificial layer down to the substrate. Metallic material is deposited to cover the photoresist mask and to at least partially fill the opening formed in the sacrificial layer without coating the overhang structure with metallic material. The sacrificial layer is dissolved to lift-off the metallic material covering the photoresist mask.
1. A method comprising:
forming a sacrificial layer having a first thickness on a top surface of a substrate;
forming a mask layer over the sacrificial layer, wherein the mask layer comprises an opening;
isotropically etching a portion of the sacrificial layer exposed through the opening of the mask layer to form an undercut region of a second thickness in the top portion of the sacrificial layer below the mask layer, wherein the undercut region defines an overhang structure, wherein the second thickness is less than the first thickness;
anisotropically etching a remaining portion of the sacrificial layer exposed through the opening of the mask layer to form an opening through the sacrificial layer down to the top surface of the substrate;
directionally depositing a metallic material to at least partially fill the opening formed in the sacrificial layer with metallic material without coating the overhang structure with metallic material; and
dissolving the sacrificial layer to lift-off the mask layer and the metallic material deposited on the mask layer thereby leaving a metal line disposed on the top surface of the substrate;
wherein the metallic material within the opening of the sacrificial layer comprises the metal line disposed on the top surface of the substrate, wherein an upper portion of the metal line comprises a tapered profile.
2. The method of claim 1 , wherein the sacrificial layer comprises a DBARC (developer-soluble bottom anti-reflective coating) material.
3. The method of claim 1 , wherein isotropically etching a portion of the sacrificial layer exposed through the opening of the mask layer comprises isotropically etching a portion of the sacrificial layer using a developer solution which is utilized during a development of a layer of photoresist material to form the mask layer.
4. The method of claim 1 , wherein forming the sacrificial layer on the substrate comprises forming a first sacrificial layer on the substrate and forming a second sacrificial layer on the first sacrificial layer;
wherein anisotropically etching a portion of the sacrificial layer comprises etching an opening through the second and first sacrificial layers down to the substrate; and
wherein isotropically etching a portion of the sacrificial layer comprises laterally etching exposed sidewall surfaces of the first sacrificial layer to undercut the second sacrificial layer and mask layer.
5. The method of claim 4 , wherein the first sacrificial layer comprises a DBARC (developer-soluble bottom anti-reflective coating) material, and wherein the second sacrificial layer comprises an ARC (anti-reflection coating) material.
6. The method of claim 1 , wherein forming the sacrificial layer on the substrate comprises forming a first sacrificial layer on the substrate and forming a second sacrificial layer on the first sacrificial layer, wherein the first sacrificial layer comprises a DBARC (developer-soluble bottom anti-reflective coating) material, and wherein the second sacrificial layer comprises a photopatternable DBARC material.
7. The method of claim 6 , wherein the process further comprises:
photolithographically patterning the second sacrificial layer concurrently with forming the mask layer to extend the opening of the mask layer through the second sacrificial layer;
wherein anisotropically etching a portion of the sacrificial layer comprises etching an opening through the first sacrificial layer down to the substrate using the mask layer and patterned second sacrificial layer as an etch mask; and
wherein isotropically etching a portion of the sacrificial layer comprises laterally etching exposed sidewall surfaces of the first sacrificial layer to undercut the second sacrificial layer and mask layer.
8. The method of claim 1 , wherein forming the sacrificial layer on the substrate comprises forming a first sacrificial layer on the substrate and forming a second sacrificial layer on the first sacrificial layer, wherein the first sacrificial layer comprises a DBARC (developer-soluble bottom anti-reflective coating) material, and wherein the second sacrificial layer comprises a photopatternable DBARC material;
wherein the method further comprises forming a hard mask layer between the second sacrificial layer and the mask layer.
9. The method of claim 8 , wherein the hard mask layer comprises silicon-ARC (anti-reflection coating) material.
10. The method of claim 8 , wherein the process further comprises:
etching the hard mask layer to transfer the opening of the mask layer to the hard mask layer;
wherein anisotropically etching a portion of the sacrificial layer comprises etching an opening through the second and first sacrificial layers down to the substrate, which corresponds to the openings in the hard mask layer and the mask layer; and
wherein isotropically etching a portion of the sacrificial layer comprises laterally etching exposed sidewall surfaces of the first sacrificial layer to undercut the second sacrificial layer and mask layer.
11. The method of claim 1 , wherein forming the sacrificial layer comprises forming two or more layers of sacrificial material.
12. The method of claim 11 , wherein each sacrificial layer comprises a DBARC (developer-soluble bottom anti-reflective coating) material.
13. The method of claim 1 , wherein the anisotropically etching comprises a reactive ion etch process.
14. The method of claim 4 , wherein the anisotropically etching comprises a reactive ion etch process.
15. The method of claim 1 , wherein the metallic material comprises titanium, palladium and gold.
16. The method of claim 8 , wherein the metallic material comprises titanium, palladium and gold.
17. The method of claim 1 , wherein forming the sacrificial layer on the substrate comprises forming a first sacrificial layer on the substrate and forming a second sacrificial layer on the first sacrificial layer, wherein the first sacrificial layer comprises a DBARC (developer-soluble bottom anti-reflective coating) material, and wherein the second sacrificial layer comprises a photopatternable DBARC material;
wherein the method further comprises:
forming a hard mask layer between the second sacrificial layer and the mask layer; and
etching the hard mask layer to transfer the opening of the mask layer to the hard mask layer;
wherein anisotropically etching a portion of the sacrificial layer comprises etching an opening through the second and first sacrificial layers down to the substrate, which corresponds to the openings in the hard mask layer and the mask layer; and
wherein isotropically etching a portion of the sacrificial layer comprises laterally etching exposed sidewall surfaces of the first sacrificial layer to undercut the second sacrificial layer and mask layer.
18. The method of claim 17 , wherein the anisotropically etching comprises a reactive ion etch process.
19. The method of claim 1 , wherein the dissolving the sacrificial layer comprises contacting the sacrificial layer with a solvent.
20. The method of claim 19 , further comprising ultrasonic agitation and heating of the solvent.