Film growth, impingement rate

Figure 1. Schematic plot of impingement rate vs. reciprocal absolute temperature showing conditions for film growth in conventional physical vapor deposition.

According to this formalism, the details of film growth (see Section 5.1.3) are described by the relative rates of processes such as the impingement and sticking rate of the adsorbate onto the substrate, desorption, surface diffusion, nucleation, attachment to an island, and coalescence. These individual rates are dependent on the deposition conditions such as the substrate temperature and the pressure of the adsorbate in the vapor phase relative to its equilibrium value, p. The dependence of the morphology on these parameters will be discussed in Section 5.1.3.2. 

Fig. 1.20. A schematic representation of several stages in the formation of a thick polycrystalline film on a substrate. Cluster formation and growth leads to impingement of cluster to form grain boundaries. The development of grain structure and subsequent film growth is determined largely by surface mobility of adatoms relative to the deposition rate and by the substrate temperature relative to the melting temperature of the film material. Adapted from Thompson (2000).

Ideally, the film thickness i.e., growth rate) will be uniform across the entire substrate surface. The flux of gas molecules that impinge on a substrate surface may be expressed as Eq. 17 ... 

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