Novel Precursors for SiCH Low-$k$ Caps beyond the 22 nm Node: Reactions of Silacyclopentane Precursors in the Plasma-Enhanced Chemical Vapor Deposition Process and Structural Analyses of SiCH Films

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To form SiCH films with high carbon content using plasma-enhanced chemical vapor deposition (PECVD), 1,1-divinylsilacyclopentane (DVScP) and 5-silaspiro[4,4]nonane (SSN) were designed as novel precursors for the low-$k$ cap layer and Cu diffusion barrier at the top of Cu lines. We elucidated the relationship between the structure of low-$k$ SiCH films made from these newly developed precursors and their barrier properties against copper and oxygen diffusion. We also studied the relationship between the structure of SiCH and the deposition process under various RF plasma powers. A Monte Carlo simulation was employed to estimate the deposition profile using an overhang test structure. Fourier transform infrared (FT-IR) spectroscopy was used to analyze the molecular structures. Our novel silacyclopentanes formed SiCH films with high carbon content and good barrier properties at high RF powers due to the specific reactions of silacyclopentanes designed according to our quantum chemical calculations. Precursor design is thus an important factor in forming SiCH with high carbon content that achieves both lower $k$ and good barrier properties.
2011-08-25