Highly robust SiCOH/mesoporous SiO2 ultralow dielectric films with heterostructures

Abstract

We report here a new dual-coating method for the deposition of SiCOH (elementally descriptive but not representing the stoichiometry) ATMS (allyltrimethylsilane) low-k films on mesoporous SiO₂ (SBA-15)/PEG (polyethylene glycol) composite films to improve the dielectric constant and mechanical properties of SiCOH/SBA-15 dual forms. The deposition was achieved via a two-step process: (i) pre-treatment, where SBA-15 was mixed with a dispersion of PEG in DI water, and SBA-15/PEG composite films were formed by spin-coating; and (ii) post-treatment, involving the deposition of SiCOH films on SBA-15s functionalized with PEGs and post-thermal annealing. In comparison with SiCOH-only films, SiCOH/SBA-15 dual forms exhibited a 20% reduction in the dielectric constant without a significant loss of mechanical properties after post-thermal annealing. SEM, TEM, XRD, BET, FT-IR, EP, and XPS results show that the enhanced electrical properties can be attributed to mesoporous SiO₂ and additional porosity gained through the removal of PEG and C_xH_y (thermally labile phases in SiCOH films) after post-thermal annealing. In the SiCOH/SBA-15 dual forms, the SBA-15 layer is expected to function as a soft layer which acts as a buffer layer to prevent the rapid decay of the modulus and hardness.