Cu Dual-Damascene Interconnects with Direct Chemical Mechanical Polishing Process on Porous Low-k Film

Abstract

To reduce the effective dielectric constant (keff) value for 32 nm node technology and beyond, the effects of a direct chemical mechanical polishing (CMP) process on porous low-k film without a protective cap layer were investigated. It was confirmed that a capless structure on porous low-k film is effective in reducing the resistance–capacitance (RC) products, but it causes degradation of wire-to-wire breakdown voltage characteristics. The most important point of a direct CMP process is to control the amount of damage to the polished surface. In this study, two types of low-k film were compared in combination with a variety of CMP process conditions. As results, we found that a direct CMP process has a positive effect on wire-to-wire current leakage and time-dependent dielectric breakdown (TDDB) reliability where a porous low-k film deposited by modified conditions is used. By optimizing the deposition and curing conditions, it is possible to control the distribution of different pore sizes in porous low-k film, which allows us to realize a highly reliable capless structure.