Dual hard mask process for low-k porous organosilica dielectric in copper dual damascene interconnect fabrication

Abstract

Using a low-k porous organosilisesqueoxane film, ALCAP"-S with k=2.1, dual hard mask (DHM) process is proposed for Cu dual damascene interconnect (DDI) formation. The porous organosilica film has very high etching rate relative to those of the hard mask (HM) andor etch-stop materials. A SiOJSiC is one of the best combinations for the DHM, in which the lower hard mask of Sic is remained after metal CMP and protects the porous film ffom the via-etching damage in misalignment region between the via-hole and the Cu-line buried. Applying insitu resist-ashing with N2/H2 gas, 0.4 p-pitched dual damascene structure is successfully fabricated. Increment of the dielectric constant is suppressed within 5% (k=2.2) after the Cu-interconnect fabrication, confirming that the DHM low-damage process is applicable for the Cu DDI fabrication in ultra low-k, porous organosilica systems.

Low Dielectric Constant Materials

“…The next step after ILD deposition is to deposit a hardmask (HM) on top of the ILD. The hardmask is often composed of two layers, HM1 and HM2 (vide infra). − The function of the hardmask is to protect the ILD from contact with the photoresist (PR) and provide a protective layer to allow rework of the PR if needed. Preventing direct contact of the photoresist with the ILD surface is dictated by the propensity of highly porous materials to absorb basic species, i.e., amines from the atmosphere, and poison the highly sensitive chemically amplified photoresists. − Photoresist rework methods, which typically use O 2 based plasmas, dictate the use of SiO 2 (HM2).…”

Low‐kMaterials: Recent Advances

“…Dense ILD is deposited at the immediate cap/ILD interface, ensuring good adhesion by eliminating the effect of porosity and then continuously increasing the porosity of the ILD until the target k is reached. Other new interfaces are created during hardmask deposition, which usually consists of two layers, HM1 and HM2, vide infra [29][30][31]. The function of the hardmask is to prevent direct contact of the photoresist (PR) with the ILD in order to eliminate the absorption of basic species, such as atmospheric amines, by the highly porous ILD, which leads to poisoning of the highly sensitive chemically amplified photoresists [32][33][34].…”

“…Although strip (resist removal) damage can be minimized with the use of hardmasks (the lithographic pattern is first transferred to the hardmask, which allows a PR strip without exposing the ILD) [29,30,[102][103][104][105], plasma damage arising from the actual ILD etch cannot be neglected. This damage manifests itself in the form of oxidative degradation of the ILD and as a result produces silica-based oxides and hydroxides at the exposed surfaces.…”

Study of Self Cross-Link Bottom Antireflective Coating and Gap Fill Materials for Sublimate Defect Reduction in ArF Lithography

“…Due to incessant demand for a smaller CD in semiconductor industries, an exposure wavelength of 193 nm is now used for less than 90 nm node photo lithography. [1][2][3] CD will continue to decrease and these in 2007 are expected to be as small as 45 nm.…”