CHEMICAL-VAPOR-DEPOSITION OF THICK TUNGSTEN COATINGS - RAMAN MEASUREMENTS AND MASS-TRANSPORT MODELING

Thick tungsten coatings have been produced by chemical vapour depositi on (CVD) from H-2-WF6 at a temperature in the range 773-1073 K under a reduced pressure. The experimental set-up is designed for in situ Ram an analysis of the gas phase (temperature and WF6 concentration) durin g the growth of tungsten coatings. A two dimensional mass transport mo del was proposed. It assumes a simple chemical pathway. Only the H-2 r eduction of WF6 has been taken into account. The major objective of th e paper is to report on the comparison between (i) the experimental de position rate and the deposition rate predicted by the model, (ii) the values of temperature and gas phase composition deduced from Raman sp ectroscopy measurements and the values of these quantities obtained by numerical calculations. These comparisons have shown the predictive c apabilities of the numerical modelling and that the temperature and WF 6 partial pressures can be recorded by a Raman equipment during the de position process.