Dissociation energetics of SiF systems of relevance to etching reactions.

Abstract

The bond energies of the 2Π and 4Σ− states of SiF, the 1Σ+ state of SiF+, the 3Σ− state of SiF−, the 1A1, 3B1, and 1B1 states of SiF2, the 2A1 state of SiF+2, and the ground states of SiH3–F, SiF3–F, SiH3–SiH3, and SiH3–SiF3 have been calculated using generalized valence bond and dissociation-consistent configuration interaction methods. Excellent bond energies are determined using only a relatively small number of configurations in the calculations. For example, the bond energy of the 2Π state of SiF is calculated to be 5.45 eV, in excellent agreement with the experimental value of 5.62 eV. For the inversion bend of SiF3 we predict that the transition state is a T-shaped configuration rather than one of D3h symmetry. Of note for the etching of solid silicon by reaction with F atoms is that unsaturated Si species react readily with F atoms to form strong bonds and that the bonding of a F atom to a lone pair of electrons on a Si atom is an activated process.

Group Members

William A. Goddard III

Charles and Mary Ferkel Professor