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 similar to 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 (CxHy), 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.