CVD IN HOT-WALL REACTORS - THE INTERACTION BETWEEN HOMOGENEOUS GAS-PHASE AND HETEROGENEOUS SURFACE-REACTIONS

The paper is concerned with chemical vapor deposition in hot wall reac tors and in particular with the interaction of homogeneous gas-phase a nd heterogeneous surface reactions. Based on model considerations it i s shown that this interaction has a tremendous influence on the deposi tion chemistry and kinetics in all cases in which the precursor gas un dergoes complex gasphase reactions. The decisive parameter determining the interaction is given by the ratio of free volume of the depositio n space and size of the surface area of the substrate; it is termed th e ''third parameter'' of chemical vapor deposition. Predictions from t he model are experimentally confirmed using results on chemical vapor deposition of pyrolytic carbon from methane. The importance of this '' third parameter'' of chemical vapor deposition in investigations of ki netics and for technical processes of chemical vapor deposition and in filtration is discussed in the conclusion.