Evaluation of Dielectric Constant through Direct Chemical Mechanical Planarization of Porous Low-$k$ Film

概要

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Nanoporous materials are utilized in back end of line (BEOL) processing of current devices. However, their low $k$-values often alter during device fabrication such as plasma processing and/or wet treatment. In this study, we analyzed the effect of chemical mechanical planarization (CMP) slurries on $k$-values, and also evaluated three types of nanoporous low-$k$ materials that were exposed to CMP slurries, dry processing, and/or barrier sputtering. We confirm that the $k$-value increase during direct CMP of porous low-$k$ films is caused by the diffusion of surfactant through the films, depending on the characteristics of the nanoporous film and surfactant. The diffusion is explained by the adsorption of surfactant on sidewalls of continuous pores formed by porogen desorption while it is easily released by post-CMP annealing. In contrast, the increase in $k$-value during CMP after dry processing is mainly caused by moisture uptake.
2010-04-25