LASER-INDUCED CONVERSION OF MOLECULAR PRECURSORS TO THIN-FILMS AND DEPOSITED LAYERS

A study has been conducted on silicon nitride deposits formed by dissociation of liquid-phase molecular precursors that were introduced directly into a laser-substrate interaction zone. An important feature of these new precursors, e.g., a silazane monomer (mol wt 220-320), is a high conversion yield from liquid to solid. Another feature is the strong absorption of 10.6-μm wavelength radiation. With use of newly designed precursors, several compounds including silicon nitride, have been formed on solid substrates and supporting grids by CO2 laser pyrolysis. Film thicknesses range from 500 Å to many microns, with growth rates as high as several microns per second. To accomplish this, a nitrogen jet is used to continuously spread the liquid precursors as a thin layer in the beam-substrate (or grid) interaction zone. In this process the precursor’s viscosity and evaporation rate are critical factors. These, together with the nature of the molecule-photon interaction and associated chemical reactions, are all factors in developing new molecular precursors. © 1990, American Chemical Society. All rights reserved.