Ab initio Molecular Orbital Study of Water Absorption and Hydrolysis of Chemical Vapor Deposited SiOF Films I

概要

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We investigated the mechanism of water absorption and hydrolysis of F-doped SiO_2 (SiOF) films using the ab initio molecular orbital (MO) method with small SiF_n(OH)_<4-n> (n = 0-3) tetrahedral model clusters. We focused on the dependence of the reactivity of these clusters with both OH^- and H_2O on the number of F atoms bonded with a Si atom. The reactivity of defect sites such as non bridging oxygens (NBOs) and free volumes around Si-F bonding were also investigated. The calculations revealed the following. SiOF films are more reactive with OH^- than with H_2O. Si atoms linked with multiple F atoms become more reactive with H_2O by reducing the activation barrier of the -OH coordination to Si, and with OH^- by increasing the stabilization energy of the pentacoordinated-Si formation. Multiple H_2O attacks at sparse, i.e., sparsely packed, network sites increase the adsorption energy and reduce the activation barrier. NBO defects also promote successive H_2O adsorption.
社団法人応用物理学会の論文
1997-04-30