Highly robust ultralow dielectric SiCOH composite films using various nanopore formation technologies

Abstract

In this thesis, the new fabrication method of highly robust low dielectric films is demonstrated by plasma-enhanced chemical vapor deposition (PECVD) with new combination of precursors. Here, we used allyltrimethylsilane (ATMS) consisting in an allyl group along with three methyl groups attached to silicon for SiCOH matrix, in order to prepare the low dielectric constant (low-k) and high modulus films by PECVD. We found that the dielectric constant and mechanical properties of the low-k material are strongly affected by the selection of precursor, the processing conditions such as a deposition temperature and post-treatment, and the introduction of a second labile phase, its chemical structure and composition. After porogen (pore generator) treatment with cyclohexene oxide (CHO), the resulting material exhibits low dielectric constant with excellent mechanical and thermal properties, having k~2.4 and 8.4 GPa of Young’s modulus. FT-IR and XPS results show that this is attributed to the desorption of labile phase ($C_xH_y$), formation of cage-like structure and change of chemical composition in the films after thermal treatment. The constituents of $SiO_2$, $SiO_3$ and SiO4 impart greater modulus and hardness to the films by increasing stable component of Si-O in the SiCOH matrix. We introduce a new dual-coating method for the deposition of SiCOH (elementally descriptive but not representing the stoichiometry) ATMS (allyltrimethylsilane) low-k films on mesoporous $SiO_2$ (SBA-15)/PEG (polyethylene glycol) composite films to improve the dielectric constant and mechanical properties of SiCOH/SBA-15 dual forms. The deposition is achieved via a two-step process: (i) pre-treatment, mixing SBA-15 with a dispersion of PEGs containing DI-water and formation of SBA-15/PEG composite films by spin-coating, and (ii) post-treatment, deposition of SiCOH films on SBA-15s functionalized with PEGs and post-thermal annealing. SiCOH/SBA-15 dual forms exhibited a 20% reduced dielec...