Formation of Ultra-Thin Pore Seal Layer on Porous Low-k Films

Abstract

In order to integrate porous dielectric materials into the next generation of Cu/low-k interconnect, the porous material has to be sealed against metal barrier precursor. We have reported pore sealants which forms ultra-thin (< 3 nm-thick) layer on top of the surface of porous low-k film while the pore sealant does not diffuse into pores. In this study, it was investigated how pore seal layer is formed on the surface of porous material and how pore mouths are sealed by pore seal layer. It was found that 1) thickness of the pore seal layer is well-controlled in the range < 5 nm, by varying spin rate and concentration of solid, 2) minimal thicknesses of the pore seal layer needed to achieve an efficient sealing for porous low-k films whose pore radius is 1.5 nm was 2.6 nm. 3) Larger pores, whose pore radius is 4.2 nm, were sealed completely with an expansion of our technology.

Surface-Localized Sealing of Porous Ultralow-k Dielectric Films with Ultrathin (<2 nm) Polymer Coating

“…Penetration of Cu and barrier metal precursors deep into the porous dielectrics is also a serious issue, which would hamper the precise control of critical dimensions (CDs) and the formation of continuous barriers, resulting in reliability degradation in ICs. , Recently, therefore, pore sealing of the porous ULK dielectrics has been intensively studied. While many types of methods have been proposed for this purpose, the drawbacks of each suggested method, such as an excessive increase of the dielectric thickness, , dielectric damage by plasmas, − a conformality issue, and difficulty in scalability, have limited their practical application to mass production. From the industrial perspective, the pore-sealing layer (PSL) must satisfy various requirements, such as a minimal effect on the low- k nature of the porous ULK dielectrics, ultrathinness of the PSL to maximize the conductor volume in a given size of line pitch, negligible damage to the dielectrics during the pore-sealing process, conformal coverage in narrow line structures, and extendibility to advanced technology nodes.…”