Magnetron sputter-deposition on atom layer scale

For many applications there is an increasing request to control the deposition process on an atom layer scale. This offers a lot of advantages like in accuracy, layer homogeneity and tailoring of layer properties. On the other hand the speed and throughput of the process should not suffer from the control on an atom layer scale as it is the case for classical atom layer deposition (ALD). For optical applications especially high-end interference filter coatings we developed a plasma assisted reactive magnetron sputtering process in combination with a high speed drive for the substrates. This combination allows controlling the layer thicknesses and layer properties on an atom layer scale while maintaining a high deposition rate. The advantages of this process are demonstrated on single layer results of SiO2, HfO2, ZrO2, Ta2O5 and mixed oxides of SiO2-Nb2O5. Morphology, surface roughness, film stress, refractive index and losses are controlled by the oxygen partial pressure, the substrate temperature, the energy input by the sputtering - and assist process and by cosputtering. The outstanding performance of high-end interference filter coatings like a multi notch filter for fluorescence microscopy is achieved by the very stable and reproducible deposition process in combination with an advanced thickness control strategy based on in-situ optical thickness control and time control.