In applied thin film deposition, perfectly vertical deposition is a rarely observed case. The geometric relation between material source and the substrate, the topography of the substrate as well as its curvature, shape and roughness rather lead to an oblique deposition geometry. Thin films deposited at oblique angles can show significant morphological differences compared to vertically deposited films. Typically the formation of porous films consisting of a large number of tilted columns is observed under non-normal deposition conditions. Deposition at highly oblique angles can furthermore be utilized to create separated nanostructures on surfaces. Techniques as oblique angle deposition (OAD) and glancing angle deposition (GLAD) evolved from this observation. Although these techniques have been used for decades, a model that is able to adequately predict the properties of the obliquely grown films has not been found yet. Especially the dependence of the tilt angle from the vapor incidence angle is discussed for many years. The tangent rule and the cosine rule (also called Tait’s rule) are well known, but give rough estimations at best. One reason for this is that neither material properties (adatom mobility, crystallinity) nor deposition parameters (substrate temperature, beam divergence) are taken into account. In a recent approach the tilt angle is connected to overhang structures. By this it is capable to include many of the mentioned influences. However, for an accurate description of oblique deposition also the growth competition has to be considered, as it plays a crucial role for the evolving film morphology.
In this contribution, a model is proposed that allows us to predict the density, growth speed and columnar tilt angle of obliquely deposited thin films for different materials over the complete angle of incidence range. The model is verified for experiments with Si, Ge and Mo, as well as for literature data.