SELF ALIGNED VIA AND PILLAR CUT FOR AT LEAST A SELF ALIGNED DOUBLE PITCH

• US 20170004996A1
• Filed: 06/30/2015
• Published: 01/05/2017
• Est. Priority Date: 06/30/2015
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Briggs, Benjamin D., Clevenger, Lawrence A., Rizzolo, Michael, Spooner, Terry A., Standaert, Theodorus E.
• Granted Patent: US 9,548,243 B1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H01L 21/0332 characterised by their composition, e.g. multilayer masks, materials
• CPC Class Codes: H01L 21/0335 characterised by their behaviour during the process, e.g. soluble masks, redeposited masks
• CPC Class Codes: H01L 21/0337 characterised by the process involved to create the mask, e.g. lift-off masks, sidewalls, or to modify the mask, e.g. pre-treatment, post-treatment
• CPC Class Codes: H01L 21/0338 Process specially adapted to improve the resolution of the mask
• CPC Class Codes: H01L 21/31053 involving a dielectric removal step
• CPC Class Codes: H01L 21/31144 using masks
• CPC Class Codes: H01L 21/76802 by forming openings in dielectrics
• CPC Class Codes: H01L 21/76816 Aspects relating to the layout of the pattern or to the size of vias or trenches layout of the interconnections per se H01L23/528; CAD of ICs G06F30/00
• CPC Class Codes: H01L 21/76831 in via holes or trenches, e.g. non-conductive sidewall liners
• CPC Class Codes: H01L 21/76877 Filling of holes, grooves or trenches, e.g. vias, with conductive material
• CPC Class Codes: H01L 21/76897 Formation of self-aligned vias or contact plugs, i.e. involving a lithographically uncritical step self-aligned silicidation on field effect transistors H01L29/665
• CPC Class Codes: H01L 23/5226 Via connections in a multilevel interconnection structure
• CPC Class Codes: H01L 23/5329 Insulating materials

Abstract

A method of forming via openings that includes forming sidewall spacers on a plurality of mandrels that are overlying a hardmask layer that is present on an interlevel dielectric layer. Etching the hardmask layer using a portion of the sidewall spacers and the plurality of mandrels to form a first pillar of hardmask material. The interlevel dielectric layer is etched using the first pillar of hardmask material as a mask to define a first via opening. The plurality of mandrels are removed. The hardmask layer is etched using the spacers to define a second pillar of hardmask material. The interlevel dielectric layer is etched using the second pillar of hardmask material to provide a second via opening.

Claims

1. A method of forming via openings comprising:

forming sidewall spacers on a plurality of mandrels that are overlying a hardmask layer, the hardmask layer being present on an interlevel dielectric layer;

etching the hardmask layer using a portion of the sidewall spacers and the plurality of mandrels to define a first pillar of hardmask material;

etching the interlevel dielectric layer using the first pillar of hardmask material and a first via etch mask to provide a first via opening;

removing the plurality of mandrels;

etching the hardmask layer using the sidewall spacers to define a second pillar of hardmask material; and

etching the interlevel dielectric layer with the second pillar of hardmask material and a second via etch mask to provide a second via opening.

2. The method of claim 1, wherein the forming of the sidewall spacers on the sidewalls on each of the plurality of mandrels that are overlying the hardmask layer comprises:

forming a layer of mandrel material on the hardmask layer;

etching the layer of mandrel material to provide the plurality of mandrels;

depositing a conformal dielectric layer of spacer material on the plurality of mandrels and exposed surfaces of the hardmask layer between adjacent mandrels of said plurality of mandrels; and

etching the conformal dielectric layer with an anisotropic etch to remove portions of the conformal dielectric layer present on an upper surface of the plurality of mandrels and portions of the conformal dielectric layer present on the hardmask layer between the adjacent mandrels, wherein a remaining portion of the hardmask layer present on sidewalls of the plurality of the conformal dielectric layer provides the sidewall spacers.

3. The method of claim 1, wherein the etching of the hardmask layer using the portion of the first spacers and the plurality of mandrels to form the first pillar of hardmask material further comprises:

forming a first pillar etch mask exposing a portion of the hardmask layer to be etched and protecting a remaining portion of the hardmask layer;

said etching the hardmask layer to provide at least two openings on opposing sides of the sidewall spacers and the plurality of mandrels that are exposed by the first pillar etch mask to form the first pillar of hardmask material; and

removing the first pillar etch mask after etching the hardmask layer to provide the first pillar.

4. The method of claim 3, wherein the etching of the interlevel dielectric layer using the first pillar of hardmask material to provide the first via opening comprises:

forming the first via etch mask over the sidewall spacers and the plurality of mandrels, the first via etch mask exposing one of the at least two openings on opposing sides of the sidewall spacers in which the first via opening is to be formed;

said etching the interlevel dielectric layer using the first pillar of hardmask material and the first via etch mask to provide the first via opening; and

removing the first via etch mask.

5. The method of claim 4, further comprising:

forming a first dielectric fill in the first via opening and between adjacent mandrels;

recessing the first dielectric fill; and

forming divot caps on the recessed surfaces of the first dielectric fill that is present in the first via opening and the first dielectric layer between the adjacent mandrels.

6. The method of claim 5, wherein said removing the plurality of mandrels comprises an etch process that removes the plurality of mandrels selectively to the sidewall spacers, the divot caps, and exposed portions of the hardmask dielectric layer.

7. The method of claim 6, wherein the etching of the hardmask layer with the sidewall spacers to provide a second pillar of hardmask material comprises:

forming a second pillar etch mask over a portion of the hardmask dielectric layer on one side of the first via opening between a recessed dielectric that was formed between adjacent mandrels and said recessed dielectric in said first via opening, the second pillar etch mask having an opening to an exposed portion the hard mask dielectric layer between said sidewall spacers;

etching the exposed portion of the hard mask dielectric layer to provide the second pillar of hardmask material, the second pillar having an exposed portion of the at least one interlevel dielectric layer on opposing sides of the second pillar; and

removing the second pillar etch mask.

8. The method of claim 7, wherein said etching the interlevel dielectric layer with the second pillar of hardmask material to provide a second via opening comprises:

forming the second via etch mask having an opening to the second pillar and the exposed portion of the at least one interlevel dielectric layer adjacent to the sidewall spacer abutting the first via opening;

said etching the interlevel dielectric layer with an anisotropic etch; and

removing the second via etch mask.

9. The method of claim 8 further comprising:

filling the second via opening with a second fill dielectric;

removing the sidewall spacers and the divot cap;

removing the first and second fill dielectric; and

filling the first and second via with an electrically conductive structure.

10. A method of forming an electrically conductive structure comprising:

etching a hardmask layer that is present atop an interlevel dielectric layer using a plurality of mandrels having dielectric spacers on sidewalls of the plurality of mandrels to define a first pillar of hardmask material;

etching the interlevel dielectric layer using the first pillar of hardmask material and a first via etch mask to provide a first via opening;

removing the plurality of mandrels;

etching the hardmask layer with the dielectric spacers to define a second pillar of hardmask material;

etching the interlevel dielectric layer with the second pillar of hardmask material and a second via etch mask to provide a second via opening; and

filling the first and second via openings with an electrically conductive material.

11. The method of claim 10, wherein the first via openings are filled with a first fill dielectric prior to removing the plurality of mandrels, and the second via openings are filled with a second fill dielectric.

12. The method of claim 10, wherein etching the hardmask layer using the portion of the dielectric spacers and the plurality of mandrels to form the first pillar of hardmask material further comprises:

forming a first pillar etch mask exposing a portion of the hardmask layer to be etched and protecting a remaining portion of the hardmask layer;

said etching the hardmask layer to provide at least two openings on opposing sides of the dielectric spacers and the plurality of mandrels that are exposed by the first pillar etch mask to form the first pillar of hardmask material; and

removing the first pillar etch mask after etching the hardmask layer to provide the first pillar.

13. The method of claim 12, wherein the etching of the interlevel dielectric layer using the first pillar of hardmask material to provide the first via opening comprises:

forming the first via etch mask over the dielectric spacers and the plurality of mandrels, the second etch mask exposing one of the at least two openings on opposing sides of the dielectric spacers in which the first via is to be formed;

said etching the interlevel dielectric layer using the first pillar of hardmask material and the first via etch mask to provide the first via opening; and

removing the first via etch mask.

14. The method of claim 12, wherein the etching of the hardmask layer with the dielectric spacers to provide a second pillar of hardmask material comprises:

forming a second pillar etch mask over a portion of the hardmask dielectric layer on one side of the first via opening between a recessed dielectric that was formed between adjacent mandrels and said recessed dielectric in said first via opening, the second pillar etch mask having an opening to an exposed portion the hard mask dielectric layer between said dielectric spacers;

etching the exposed portion of the hard mask dielectric layer to provide the second pillar of hardmask material, the second pillar having an exposed portion of the interlevel dielectric layer on opposing sides of the second pillar; and

removing the second pillar etch mask.

15. The method of claim 14, wherein said etching the interlevel dielectric layer with the second pillar of hardmask material to provide a second via opening comprises:

forming a second via etch mask having an opening to the second pillar and the exposed portion of the interlevel dielectric layer adjacent to the dielectric spacer abutting the first via opening;

said etching the interlevel dielectric layer with an anisotropic etch; and

removing the second via etch mask.

16. The method of claim 11, wherein filling the first and second via openings with the electrically conductive material comprises:

recessing the second fill dielectric in the second via opening;

removing the dielectric spacers;

removing the hardmask layer;

removing the first fill dielectric in the first via opening and the second fill dielectric in the second via opening; and

said filling the first and second via openings with said electrically conductive material.

17. A method of forming via openings comprising:

forming a first set of spacers on sidewalls of a first set of mandrels, the first set of mandrels present on a material layer for forming a second mandrel that is present overlying at least one interlevel dielectric layer;

etching the mandrel material layer using the first set of spacers as an etch mask to form a second set of mandrels, wherein etching the mandrel material layer includes removing the first set of mandrels

forming a second set of spacers on the second set of mandrels;

etching the hardmask layer using the second set of spacers on the second set of mandrels to define a first pillar of hardmask material;

etching the interlevel dielectric layer using the first pillar of hardmask material and a first via etch mask to provide a first via opening;

removing the second set of mandrels; and

forming a second via opening in the interlevel dielectric layer.

18. The method of claim 17, wherein removing the second set of mandrels comprises:

depositing a first fill dielectric in the first via opening;

planarizing to remove the first set of spacers; and

said removing said second set of mandrels with an etch process.

19. The method of claim 18, wherein said forming the second via opening comprises:

forming a pillar etch mask having an opening exposing a portion of the hardmask layer and the second set of spacers;

etching the portion of the hardmask layer exposed by the pillar etch mask to form a second pillar of hardmask material;

forming a second via mask having an opening exposing a portion of the at least one interlevel dielectric layer through an opening through the hardmask layer that is adjacent to the second pillar of hardmask material; and

etching the second via opening into the at least one interlevel dielectric.

20. The method of claim 17 further comprising filling the first via opening and the second via opening with an electrically conductive material.