Spin-on silicon oxide (SOX) III: Light scattering of the sol.

This paper describes an analysis of the physical properties of a sol/gel of silicic acid in propanol solution using several complementary light scattering techniques. We followed polymerization and aggregation processes through time-dependent changes in the size, shape, and density of the sol particles. In addition, the index of refraction and pH of the sols were monitored. We identified three different particle-growth regimes in which the particle density increases, decreases, or remains constant. We were able to correlate the sol experimental data with wet- etching rates of the cured films. High-density cured oxide films (etching rates 1500angstrom/min) were spin-coated from sols with three common characteristics: an average particle diameter >450angstrom, a relatively high polydispersity, and a low particle density.