Browsing by Author "Leu, J."

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A detailed ellipsometric porosimetry and positron annihilation spectroscopy study of porous organosilicate-glass films with various ratios of methyl terminal and ethylene bridging groups
(2020-10-15)
Rasadujjaman, M.
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Wang, Y.
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Zhang, L.
;
Naumov, S.
;
Attallah, A. G.
Organosilicate-glass films with a varying ratio of terminal methyl and bridging ethylene groups are synthesized using 1,2-bis(trimethoxysilyl)ethane/methyltrimethoxysilane mixtures and sol-gel technology. The films are characterized by Fourier Transform Infrared spectroscopy, Ellipsometric Porosimetry and Positron Annihilation Spectroscopy. The hard bake at 400 degrees C generates the final pore structure, which depends on the curing environment. It is shown that ethylene bridge is destructed during the hard bake in the air via formation of peroxide radicals that form equivalent to SiOH during the transformation. Continuous hard bake leads to condensation of silanol groups and form a structure similar to the ordinary silica. The pore size of highly porous materials (>30%) is larger in air cured films. Destruction of the ethylene bridge makes the films matrix soft and micropores collapse due to the capillary forces during the template evaporation. It leads to the film shrinkage, increases the size of internal voids. The air cured samples showed better mechanical properties than N2 cured ones although in the last case ethylene bridging groups were preserved. The reason is that the collapse of micropores increase the internal density and creates more favorable condition for condensation of silanol groups.
Effect of the C-bridge on UV properties of organosilicate films
(2019-09-01)
Seregin, D. S.
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Naumov, S.
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Chang, W-Y
;
Wu, Y-H
;
Wang, Y.
Carbon-bridged organosilicate films deposited by using different precursors are studied by both experimentally and theoretically. It is shown that carbon-bridged OSG films have higher Young Modulus (E) than methyl-terminated films and E(phenylene) > E(ethylene) > E(methylene). However, the k-values of these films show the same tendency and this is one of the drawbacks of carbon terminated materials when they are considered as low-k candidates. It is shown that the films having a phenylene bridge can be destructed by UV light with wavelength > 200 nm while ethylene or an ethylene bridged samples are stable. Mechanism of UV initiated destruction of phenylene bridged materials is analyzed by using quantum chemical calculations. The presented results allow to conclude that the presence of long aliphatic and aromatic bridges makes OSG materials more sensitive to UV light
Synthesis, Pore Morphology, and Dielectric Property of Mesoporous Low-k Material PSMSQ using a Reactive High-Temperature Porogen, TEPSS
(2011)
Chiu, S. -Y.
;
Hsu, H. L.
;
Che, M. L.
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Leu, J.
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材料科學與工程學系
A high-temperature reactive porogen, triethoxy(polystyrene) silane (TEPSS) (M-w=3,500 g/mole), suitable for late-porogen removal integration scheme has been synthesized in p-xylene via atom transfer radical polymerization. TEPSS was then grafted onto poly(methyl-silsesquioxane) (MSQ) matrix (k=2.9) to circumvent possible phase separation between matrix and porogen in the hybrid approach and porogen aggregation. Our results shows porous low-k MSQ films possess uniform pore size, 24 nm for porosity up to 40%, primarily due to low PDI and reactive porogen, and the dielectric constant is decreased to 2.37 at 40% porosity. In addition, less porogen aggregation was observed at porogen loading similar to 40 v%.