The Chemistry of CVD

Before any CVD program is undertaken, it is essential to evaluate all the potential reactions and select the most appropriate. This is done by a thermodynamic analysis as described in Ch. 2 and, if necessary, by an experimental program. 

The CVD reactions can be classified in several major categories which are outlined below. These reactions and others are described in greater detail in Chs. 6-11 where the materials produced by CVD are reviewed. 

Metallo-organic CVD (MOCVD) is major area of CVD which is rapidly growing, particularly in semiconductor and optoelectronic applications. It is treated separately in Ch. 4. 

In thermal-decomposition reactions, a molecule is split into its elements and/or a more elementary molecule. Such reactions are the simplest since only one precursor gas is required. Typical examples are as follows  

This reaction is used extensively in the production of carbon, graphite and diamond. 

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This is by no means an exhaustive review of all ceramic materials deposited by CVD. The materials discussed were chosen to illustrate the chemistry of CVD, and articles and reviews that indicate the current direction of research are presented. 

Jain, A., etal., Recent Advances in Copper CVD, /w/co afemetallo-organic CVD of copper. 

Tetravalent silicon is the only structural feature in all silicon sources in nature, e.g. the silicates and silica even elemental silicon exhibits tetravalency. Tetravalent silicon is considered to be an ana-logon to its group 14 homologue carbon and in fact there are a lot of similarities in the chemistry of both elements. Furthermore, silicon is tetravalent in all industrially used compounds, e.g. silanes, polymers, ceramics, and fumed silica. Also the reactions of subvalent and / or low coordinated silicon compounds normally lead back to tetravalent silicon species. It is therefore not surprising that more than 90% of the relevant literature deals with tetravalent silicon. The following examples illustrate why "ordinary" tetravalent silicon is still an attractive field for research activities Simple and small tetravalent silicon compounds - sometimes very difficult to synthesize - are used by theoreticians and preparative chemists as model compounds for a deeper insight into structural features and the study of the reactivity influenced by different substituents on the silicon center. As an example for industrial applications, the chemical vapor decomposition (CVD) of appropriate silicon precursors to produce thin ceramic coatings on various substrates may be mentioned. 

Hampden-Smith MJ, Kodas TT (eds) (1994) In The chemistry of metal. CVD, Verlag Chemie, Weinheim... 

Kodas TT, Hamden-Smith MJ (1994) The chemistry of metal CVD. VCH, Weinheim, Germany... 

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