UNDERSTANDING GAS-PHASE REACTIONS IN THE THERMAL CVD OF HARD COATINGSUSING COMPUTATIONAL METHODS

This article provides a short summary of the theoretical approaches to understanding gas-phase reactions. In particular, the quantum-chemica l bond-additivity correction (BAC) method for predicting molecular the rmochemistry of gas-phase molecules is described. A brief discussion o f the use of RRKM methods for predicting the rates of unimolecular rea ctions and of ab initio methods for predicting the rates of bimolecula r reactions is also presented. Finally, the question of when gas-phase reactions are likely to be important in CVD is discussed. Criteria ar e proposed for performing a first-order evaluation of the extent of pr ecursor pyrolysis in the CVD of hard coatings. Examples from the CVD o f titanium-containing species, boron nitride, and silicon carbide will be used for illustration. (C) 1998 Elsevier Science S.A. All rights r eserved.