Effect of terminal methyl groups concentration on properties of organosilicate glass low dielectric constant films

Abstract

Surfactant-templated organosilicate glass (OSG) based low-k films are deposited by using tetraethyl orthosilicate/methyltriethoxysilane (TEOS/MTEOS) mixture with different ratio and spin-on technology with the goal of understanding the effects of terminal methyl groups on chemical and structural properties. It is shown that despite of constant surfactant concentration these films have quite different properties when the changing of CH3/Si ratio. The most important changes are related to change of their hydrophilicity, change of mechanical properties, the pore size and to the shift of Si–CH3 peak position in Fourier transform infrared (FTIR) spectra. The films are becoming hydrophobic if they are deposited from sols with CH3/Si ratio higher than 0.2. The Young’s modulus gradually decreases with increasing the terminal methyl groups concentration in the films. The pore size increases with concentration of methyl groups and changes from cylindrical to ink-bottle shape. The nature of SiCH3 peak shift is explained by using molecular mechanics simulation. It is shown that the reason of this shift is change of dπ–pπ hybridization in Si–O–Si bonds, which is affected by presence of CH3 group.