A practical model to enable the prediction of coating thickness variations across a flat surface

The presented model enables lateral coating thickness uniformity across a flat surface to be predicted from only a limited amount of actually measured thickness data. It is based on an inverse power law relationship for the reduction of coating thickness with increasing source to substrate distance, and is essentially a variation of the well known cosine law. The value of the power in the expression determines the coating thickness profile. The model is shown to work successfully for coatings produced by techniques based on electron beam evaporation, including vacuum evaporation, gas evaporation and PAPVD, and is compared with other available thickness models. It is also shown to have some applicability in the case of magnetron sputtering systems, both balanced and unbalanced.