Advanced Direct-CMP process for porous low-k thin film

In order to reduce the effective dielectric constant (keff) for the 32 nm technology node and beyond, Direct-CMP of a porous low-k film without a protective cap layer is required. However, the degradation of breakdown electric field (Ebd) has been one of critical issues. This study clarified that the Ebd degradation was caused by the pit defects on the surface of porous low-k film during Direct-CMP. In order to suppress the pit defects, we evaluated dependency of micro-pores density of CMP pads. As a result, we demonstrated that CMP pads with low-density micro-pores drastically reduced them and improved the Ebd degradation. In this paper, the mechanism for their reduction is also discussed.