Nanoporous SiCOH/CxHy dual phase films with an ultralow dielectric constant and a high Young's modulus

Abstract

We used plasma-enhanced chemical vapor deposition (PECVD) of allyltrimethylsilane (ATMS), consisting of an allyl group along with three methyl groups attached to silicon, to form a low dielectric constant (low-k) and high modulus SiCOH matrix. We found that the dielectric constant and mechanical properties of the low-k material are strongly affected by the selection of the precursor, processing conditions such as the deposition temperature and post-treatment, the introduction of a second labile phase, and the chemical structure and composition of the films. After porogen (pore generator) treatment with cyclohexene oxide (CHO), the resulting material exhibited a low dielectric constant with excellent mechanical and thermal properties, having k ∼ 2.4 and a Young's modulus of 8.4 GPa. FT-IR and XPS results show that this is caused by the desorption of the labile phase (C_xH_y), the formation of Si–O cage-like structures, and changes in the chemical composition of films after thermal treatment. SiO₂, SiO₃, and SiO₄ impart greater modulus and hardness to the films by increasing the stable component of Si–O in the SiCOH matrix.