Film Formation and Structure Zone Model

Thin-film formation is described as a sequential process which includes nucleation, coalescence and subsequent thickness growth, whereby all states can be influenced by deposition parameters, such as temperature, pressure, gas flow rate, etc. [3,4], For physical vapour deposition (PVD) processes, significant works have been published and progess made in understanding the microstructure evolution of the films. In the atomistics of growth processes, there exists much in common bewteen CVD and PVD. Theories from PVD processes can thus be used to analyse the microstructure evolution of CVD processes [5, 6], 

1 Three-dimensional Island Mode (Volmer-Weber Mode) 

This occurs when stable clusters small, form on the substrate surface and grow in three dimensions to form separate islands. This happens when the bonding between atoms in the clusters is much greater and stronger than that between the atom and the substrate. Many systems of metals on the insulators of micro-electronic devices display this mode of growth, such as silicon growth an Si02 substrate reported by Bloem [8], 

2 Layer-by-layer Mode (Frank- Van Der Merwe Mode) 

This is a kind of two-dimensional growth mode, and layers of the deposit grow on the surface of another layer. In this case, the atomic bonding between the substrate surface and the film is greater than that between atoms of adjacent film layers. The homoepitaxial growth of Si thin film Si substrate belongs to this mode. 

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