Chemical Vapour Deposition Precursors and Their Classification

2 Chemical Vapour Deposition Precursors and Their Classification 

The precursors used in the CVD process can be divided into three categories as follows [7, 8]  

These precursors are very simple and generally consist of small molecules where the central species is bonded to other species such as a halide (F, Cl, less commonly Br or I). Some of the halides are solid at room temperature (e.g. A1C13, WCI5 and ZrCl4 etc.) and their sublimation is difficult to control. In such cases in situ halogenation is usually used to form the halide precursor, which is then conveyed to the reaction chamber by the carrier gas. 

Halides are often used for the deposition of high-temperature materials (such as refractory metals and advanced ceramics) with a high growth rate. They are also 

These compounds are used as the precursors for MOCVD processes. Compared with halides and hydrides, the metal-organic compounds have much more complex structures because they contain large functional groups (e.g. allyl, butyl, methyl etc) and ligands (such as carbonyl, acetylacetonate, hexafluoroacetyl acetonate and so forth). Some representative examples are listed below [19,22]  

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