Chemical Vapour Deposition of Thick Tungsten Coatings : Raman Measurements and Mass Transport Modelling

Abstract

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