Sample CVD and ALD processes

We turn finally to several examples of CVD and ALD processes that illustrate the issues described above. Many CVD processes take advantage of temperature 

At lower temperatures the exothermic deposition reaction dominates. The temperature gradient in the sealed reactor tube leads to net transport of Si from a source to the substrate. 

A relatively simple but technologically interesting material that can be conveniently deposited by CVD is SiC. SiC is typically produced by reaction of a small organic molecule such as propane (CsHg) with silane (SiH4) in a hydrogen ambient. This reaction has been studied in some detail. For a detailed discussion see, for example. Reference [14]. The reaction runs both forward and in reverse depending upon temperature and H2 partial pressure. 

This can only occur where Si is available as a reactant. An Si02 layer does not react with WFg as it is too stable. Therefore, it makes a good mask. This means that W 

The reaction is strongly catalyzed by the presence of W, thus it proceeds most rapidly where a pre-existing W layer is present. Because it does not require Si reactant from the substrate it proceeds without further consumption of the substrate. 

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