J. Phys. IV France 05 (1995) C5-105-C5-112
Kinetic Processes in the CVD of SiC from CH3SiCl3-H2 in a Vertical Hot-Wall ReactorF. Langlais1, F. Loumagne1, D. Lespiaux1, S. Schamm2 and R. Naslain1
1 Laboratoire des Composites Thermostructuraux, UMR 47, CNRS-SEP-UBI, Domaine Universitaire, 3 Allée de La Boëtie, 33600 Pessac, France
2 Centre d'Elaboration de Matériaux et d'Etudes Structurales, Laboratoire d'optique Electronique, UPR 8011 du CNRS, BP. 4347, 31055 Toulouse cedex, France
The chemical vapour deposition of SiC-based ceramics from the CH3SiCl3-H2 precursor is investigated on the basis of large scale experimental and theoretical approaches. The use of a vetirtical cylindrical hot-wall LPCVD reactor permits to get a wide isothemal reaction zone with a creeping laminar flow around the substrate and a largely chemical control of the kinetics, which favours a high supersaturation and a nucleation regime. A calculation of the coverage of C (111) or Si(111) planes of SiC points out the importance of the chemisorption of SiCl3 and H radicals on C atoms and of CH3 and Cl radicals on Si atoms. On the basis of kinetic experiments and of chemical and structural investigations of the deposits, several domains of conditions are defined with different rnechanisms for the formation of SiC-based ceramics. For low temperatures and low pressures, a regime of growth of stoichiometric SiC microcrystals occurs from reaction of CH3 and SiCl3 intermediates. Higher pressures in the chemical control knetic domain, favour a regime of nucleation of nanocrystals with an excess of silicon resulting from SiCl3/SiCl2 silicon precursor.
© EDP Sciences 1995