A highly reliable, 65nm-node Cu interconnect technology has been developed with I 80nndZOOnm-pitched lines COnneCted through $IOOnm-vias. A porous SiOCH film (k=2.5) with sub-nanometer pores is introduced for the inter-metal dielectrics (IMD) on a non-porous, rigid SiOCH film (k=2.9) for the via-intra-line dielectrics (via-ILD). A key breakthrough is a special pore-seal technique, in which the trench-etched surface of the porous SiOCH is covered with an ultra-thin, low-k organic silica film (k=2.7), thus improving the lineto-line TDDB reliability of the narrow-pitched Cu lines.The filly-scaled-down, 65nm-node Cu interconnects with the porous-on-rigidSiOCH hybrid structure achieve excellent performance and reliability.

Hybrid-type, Cu dual damascene interconnects (DDI) are fabricated in a porous organosilica film (k=2.1) inserted between low-k films of hard-mask (HM) and etch-stop (ES) layers, Plasma-polymerized, divinyl siloxane bisbenzocyclobutene @-BCB, k=2.7) film, instead of SiCN film (k>4), is selected for these HM and ES layers due to the low k-value as well as the high etch-stop property to the porous film. The line capacitance in the hybrid-type, Cu-DDI with BCB-HM and BCB-ES layers decreases 20% compared with that of the Cu-DDI with SO,-HM and SiCN-ES layers, achieving the effective dielectric constant (k.,J of 2.6. This new interconnect sttucture is a strong candidate for the 70nm-node ULSls.

The dielectric constant dependence of the mechanical strength and the adhesion strength is investigated using porosity-controlled low-k films, and a material parameter is clarified to suppress the chemical mechanical polishing (CMP)-related defects in Cu damascene interconnects. Mechanical strengths such as the modulus and hardness of low-k films decreased as the dielectric constant decreased. Adhesion energy between the low-k films and an upper hard-mask layer (HM) of PECVD-SiO2 strongly depends on the dielectric constant of low-k films, while adhesion energy between the low-k films and a lower etch stop layer (ES) of SiCN shows weak dependence. It was found that the adhesion energy between the upper SiO2 and the low-k film is a critical mechanical parameter for diminishing the CMP-related defects. Introducing a porous low-k film, methylsilsesquiazane (k=2.64), with high adhesion to the HM-SiO2, we successfully fabricated single damascene copper interconnects within an acceptable limit of CMP-related defects.

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.

No abstract