Isobutyl Silane Precursors for SiCH Low-k Cap Layer beyond the 22 nm Node: Analysis of Film Structure for Compatibility of Lower k-value and High Barrier Properties

Abstract

To form SiCH films with a high carbon content using plasma-enhanced chemical vapor deposition (CVD), isobutyl trimethylsilane (iBTMS) and diisobutyl dimethylsilane (DiBDMS) were examined as precursors for a 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 in an overhang test structure. Fourier transform infrared spectroscopy (FT-IR) was used to analyze molecular structures. Our studies indicate that deposition conditions cannot dictate carbon content, but can control porosity/density. Precursor selection is thus an important factor in forming SiCH with a high carbon content that achieves both lower k and good barrier properties.