Analytical Study of Porous Organosilicate Glass Films Prepared from Mixtures of 1,3,5- and 1,3-Alkoxysilylbenzenes

Md Rasadujjaman; Xuesong Wang; Yanrong Wang; Jing Zhang; Valeriy E Arkhincheev; Mikhail R Baklanov

doi:10.3390/ma14081881

Analytical Study of Porous Organosilicate Glass Films Prepared from Mixtures of 1,3,5- and 1,3-Alkoxysilylbenzenes

Materials (Basel). 2021 Apr 9;14(8):1881. doi: 10.3390/ma14081881.

Authors

Md Rasadujjaman^{1

2}, Xuesong Wang¹, Yanrong Wang¹, Jing Zhang¹, Valeriy E Arkhincheev^{3

4}, Mikhail R Baklanov^{1

5}

Affiliations

¹ Department of Microelectronics, North China University of Technology, Beijing 100144, China.
² Department of Physics, Dhaka University of Engineering & Technology, Gazipur 1707, Bangladesh.
³ Laboratory of Applied Physics, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City 729000, Vietnam.
⁴ Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City 729000, Vietnam.
⁵ Research and Education Center "Technological Center", MIREA-Russian Technological University, 119454 Moscow, Russia.

Abstract

Organosilicate glass (OSG)-based porous low dielectric constant (low-k) films with different molar ratios of 1,3,5-tris(triethoxysilyl)benzene to 1,3-bis(triethoxysilyl)benzene bridging organic groups (1:3 and 1:7) were spin-on deposited, followed by a soft bake in air and N₂ at 150 °C and hard bake in air and N₂ at 400 °C. Non-ionic template (Brij^®30) concentrations were varied from 0 to 41 wt% to control the porosity of the films. The chemical composition of the matrix of the films was evaluated and discussed with the shrinkage of the film during the curing, refractive indices, mechanical properties, k-values, porosity and pore structure. The chemical composition of the film cured in both air and N₂-containing ambient were evaluated and compared. The benzene bridging groups containing films change their porosity (0 to 43%) but keep the pore size constant and equal to 0.81 nm when porosity is lower than 30%. The k-value decreases with increasing porosity, as expected. The films containing benzene bridge have higher a Young's modulus than plasma-enhanced chemical vapor deposition (PECVD) methyl-terminated low-k films with the same porosity and show good hydrophobic properties after a hard bake and close to the values reported for 1,4-benzene-bridged films. The fabricated films show good stability after a long time of storage. However, the improvement of mechanical properties was lower than the values predicted by the published literature data. It was concluded that the concentration of 1,3,5-benzene bridges was below the stiffness threshold required for significant improvement of the mechanical properties. The films show UV-induced luminescence with a photon energy of 3.6 to 4.3 eV. The luminescence is related to the presence of oxygen-deficient-type defects or their combination with organic residues. The most intensive luminescence is observed in as-deposited and soft bake samples, then the intensity is reduced after a hard bake. It is assumed that the oxygen-deficient centers form because of the presence of Si-OC₂H₅ groups in the films and the concentration of these centers reduces when all these groups completely transformed into siloxane (Si-O-Si).

Keywords: FTIR; Young’s modulus; benzene bridges; dielectric constant; ellipsometric porosimetry; low-k films; organosilicate glass; pore structure; thermal stability.

Abstract

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