Ta/low-κ CMP with Colloidal Silica Particles

Abstract

AbstractLow-κ/Cu interconnect integration achievement is one of the key issues for the future sub-100 nm technologies. Nowadays, no definitive integration scheme has been reported. Low-κ integration is especially difficult because the trench/via etching and CMP processes can damage its properties. In the present work, we present results on different materials that could be used in such integration. We focused our study on the barrier (Ta/TaN) and on a low-κ material (dense and porous), that is a spin-on-dielectric (SOD) of the methylsilsesquioxane (MSQ) type. CMP slurries were made from monodisperse colloidal silica particles. In a first approach, the slurries compositions mainly differed by their pH and abrasive characteristics. The particle size ranged from 12 to 80 nm, with a pH varying between 2 and 11. The sensitivity of the Ta/TaN and low-κ removal rates will also be reported. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) of the different films were carried out in order to evaluate the impact of CMP on their surface quality. Measurements did not show any surface degradation or/and scratches, and no delamination has been observed. Post-CMP κ value measurements have been carried out to highlight possible damage on the low-ê dielectric materials.