CN-121986598-A - Air gap structure in interconnect with top via

Abstract

A back-end-of-line (BEOL) interconnect structure is provided that includes a top via structure located on a metal line. An air gap is located adjacent to and surrounding the metal line and the top via structure. The air gap includes a lower portion located adjacent to the metal line and an upper portion located adjacent to the top via structure. Such an air gap can be extended for BEOL interconnect scaling below 2nm technology nodes. Methods of forming such BEOL interconnect structures are also provided.

Inventors

• A. Duta
• K. Leders
• YANG ZHICHAO

Assignees

• 国际商业机器公司

Dates

Publication Date

20260505

Application Date

20240911

Priority Date

20231016

Claims (20)

1. 1. A post process BEOL interconnect structure comprising: A top via structure on the metal line, and An air gap located adjacent to and surrounding both the metal line and the top via structure, wherein the air gap has a lower air gap portion located adjacent to the metal line and an upper air gap portion located adjacent to the top via structure.
2. 2. The BEOL structure of claim 1 wherein a lower air gap portion of the air gap has a first width and an upper air gap portion of the air gap has a second width, wherein the first width is different than the second width.
3. 3. The BEOL structure of claim 2 wherein the first width is greater than the second width.
4. 4. The BEOL structure of claim 1 wherein the air gap extends substantially to a topmost surface of the top via structure.
5. 5. The BEOL structure of claim 1 wherein a portion of the air gap is sandwiched between a first dielectric liner and a second dielectric liner.
6. 6. The BEOL structure of claim 5 wherein the first dielectric liner is located on sidewalls of the metal lines and sidewalls of the top via structure.
7. 7. The BEOL structure of claim 5 further comprising an interlayer dielectric layer located on the second dielectric liner and having a topmost surface substantially coplanar with a topmost surface of the top via structure.
8. 8. The BEOL structure of claim 7 further comprising an air gap region sealant layer on the interlayer dielectric layer and on top of the top via structure, wherein the air gap region sealant layer extends over the air gap.
9. 9. The BEOL structure of claim 1 wherein the air gap is spaced apart from the metal line and top via structure by a dielectric liner.
10. 10. The BEOL structure of claim 9 further comprising an additional metal line located near the metal line under the top via structure.
11. 11. The BEOL structure of claim 10 further comprising a dielectric layer over the additional metal lines, wherein dielectric layer has a middle portion and an end portion, the middle portion having a first thickness, the end portion having a second thickness, wherein the first thickness is greater than the second thickness.
12. 12. The BEOL structure of claim 11 further comprising an interlayer dielectric layer located on the dielectric layer and having a topmost surface substantially coplanar with a topmost surface of the top via structure.
13. 13. The BEOL structure of claim 12 further comprising an air gap region sealant layer on the interlayer dielectric layer and on top of the top via structure, wherein the air gap region sealant layer extends over the air gap.
14. 14. The BEOL structure of claim 1 further comprising a substrate located under the metal lines, wherein the substrate comprises at least one lower interconnect level, an intermediate process MOL level, a prior process FEOL level, or any combination thereof.
15. 15. A method of forming a post-process BEOL interconnect structure, the method comprising: forming a top via structure on the metal line; Forming a first dielectric liner over all physically exposed surfaces of the metal lines and the top via structures; forming a sacrificial liner around the metal line and the top via structure and over the first dielectric liner; Forming a second dielectric liner over the sacrificial liner; forming an interlayer dielectric layer on the second dielectric liner; Removing the sacrificial liner to form an air gap region, and An air gap region sealant layer is formed to close the air gap region to form an air gap.
16. 16. The method of claim 15, wherein the air gap has a lower air gap portion located near the metal line and an upper air gap portion located near the top via structure.
17. 17. The method of claim 16, wherein the lower air gap portion has a first width and the upper air gap portion has a second width, wherein the first width is different than the second width.
18. 18. The method of claim 17, wherein the first width is greater than the second width.
19. 19. The method of claim 17, wherein the air gap extends substantially to a topmost surface of the top via structure.
20. 20. The method of claim 15, wherein removing the sacrificial liner comprises wet etching or isotropic dry etching.

Description

Air gap structure in interconnect with top via Technical Field The present application relates to semiconductor technology and, more particularly, to back-end-of-the-line (BEOL) interconnect structures that include air gaps located near metal lines and top via structures and methods of forming such structures. Background In general, BEOL interconnect devices include a plurality of circuits that form Integrated Circuits (ICs) fabricated on a BEOL interconnect substrate. Complex signal path networks are typically routed to connect circuit elements distributed across the surface of a substrate. Efficient routing of these signals across devices requires the formation of multilevel or multi-level schemes such as, for example, single damascene or dual damascene wiring structures (i.e., interconnects). The design and layout of BEOL interconnects on an IC is critical to its normal function, performance, power efficiency, reliability, and manufacturing yield. In a typical BEOL interconnect structure, conductive metal vias run perpendicular to the interconnect substrate, while conductive metal lines run parallel to the interconnect substrate. Typically, a conductive metal via exists under a conductive metal line and both features are embedded within an interconnect dielectric material layer. Disclosure of Invention A BEOL interconnect structure is provided that includes a top via structure on a metal line. An air gap is located adjacent to and surrounding the metal line and the top via structure. The air gap includes a lower portion located adjacent to the metal line and an upper portion located adjacent to the top via structure. Such an air gap can be extended for BEOL interconnect scaling below 2nm technology nodes. Methods of forming such BEOL interconnect structures are also provided. In one aspect of the present application, a BEOL interconnect structure is provided. In one embodiment of the present application, the BEOL interconnect structure includes a top via structure located on a metal line. An air gap exists adjacent to and surrounding both the metal line and the top via structure. Notably, the air gap has a lower air gap portion located near the metal line and an upper air gap portion located near the top via structure. In another aspect of the present application, a method of forming a BEOL interconnect structure is provided. In one embodiment, the method includes forming a top via structure over a metal line, forming a first dielectric liner over all physically exposed surfaces of the metal line and the top via structure, forming a sacrificial liner over the first dielectric liner surrounding the metal line and the top via structure, forming a second dielectric liner over the sacrificial liner, forming an interlayer dielectric layer over the second dielectric liner, removing the sacrificial liner to form an air gap region, and forming an air gap region sealant layer to close the air gap region to form an air gap. In another embodiment, the method includes forming a top via structure over a metal line, forming a dielectric liner over all physically exposed surfaces of the metal line and the top via structure, forming a sacrificial liner over the dielectric liner around the metal line and the top via structure, forming a dielectric layer over a portion of the dielectric liner by a selective deposition process, forming an interlayer dielectric layer over the dielectric layer, removing the sacrificial liner to form an air gap region, and forming an air gap region sealant layer to close the air gap region to form an air gap. Drawings Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a cross-sectional view of an exemplary structure that may be employed in accordance with an embodiment of the present application, including metal lines and top via structures on a substrate. Fig. 2 is a cross-sectional view of the exemplary structure shown in fig. 1 after forming a first (inner) dielectric liner on all physically exposed surfaces of the metal lines and the top via structure. Fig. 3 is a cross-sectional view of the exemplary structure shown in fig. 2 after forming a sacrificial liner over the first dielectric liner. FIG. 4 is a cross-sectional view of the exemplary structure shown in FIG. 3 after removal of the sacrificial liner from the horizontal surface of the structure. Fig. 5 is a cross-sectional view of the exemplary structure shown in fig. 4 after formation of a second (outer) dielectric liner. Fig. 6 is a cross-sectional view of the exemplary structure shown in fig. 5 after formation of an interlayer dielectric (ILD) layer. FIG. 7 is a cross-sectional view of the exemplary structure shown in FIG. 6 after removal of the remaining sacrificial liner to form an air gap region. Fig. 8 is a cross-sectional view of the exemplary structure shown in fig. 7 after forming an air gap region sealant layer to close the air gap re