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Mass Spectrometry of Spin-On-Glass Low-K Dielectric Precursors



William E. Wallace, Kathleen M. Flynn, Joseph M. Antonucci


The degree-of-intramolecular-condensation, defined as the number of residual silanol (SiOH) groups per oligomer, for a variety of silsesquioxane polymers was measured by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Reaction between SiOH groups within individual silsesquioxane molecules leads to the formation of Si-O-Si bridges accompanied by the loss of water. This elimination reaction is easily identified via high-resolution time-of-flight mass spectrometry. Each intramolecular bridge formed corresponds to a closed topological loop in the molecule, for example, a cubic molecule would have eight silicon atoms and six closed loops. High degrees of condensation result in closed polyhedral structures that inhibit gelation of the synthesis products, while low degrees of condensation result in highly-branched structures that encourage gelation. Ladder structures have topologies between those of closed polyhedra and highly-branched structures. We demonstrate how such structures can be identified by mass spectrometry.
Polymer Preprints


dielectric, hydrolysis-condensation, mass spectrometry, siloxane, silsesquioxane


Wallace, W. , Flynn, K. and Antonucci, J. (2001), Mass Spectrometry of Spin-On-Glass Low-K Dielectric Precursors, Polymer Preprints, [online], (Accessed March 1, 2024)
Created April 1, 2001, Updated February 19, 2017