Architectural glass has to meet increasingly strict requirements in modern building construction, and not only because the area is often very large. Speciality glass must have an excellent appearance in addition to providing thermal and sound insulation. How good the characteristics are depends primarily on the surface coating.
The Fraunhofer Institute for Surface Engineering and Thin Films IST in Braunschweig has developed a new module for a sputtering system, the Megatron®, which is able to significantly improve the efficiency of this coating method. With suitable material combinations such as titanium oxide as a tubular target and wolfram as a planar target, the sputtering rate is increased by 100 percent compared to the conventional sputtering process. The new module is ready for series production and can be retrofitted.
An additional planar (flat) target made of a heavy element is arranged behind each target tube in the new coating module. Ionised inert gas releases atoms from the flat solid and gradually “implants” them in the tubular target, so that more coating material can be released from the solid due to the implantation of a heavy element (wolfram). This results in a higher coating rate and a more homogeneous surface layer.
Furthermore, using two separate targets makes it possible to mix a wide variety of elements and to precisely configure the doping concentration, which can be changed across the layer thickness as desired. Entirely new material combinations can also be produced with sputtering.
Simulation to reach the goal faster
Process simulation was indispensable in the development of the new Megatron® coating module. A parallel Particle-in-Cell Monte-Carlo (PIC-MC) simulation software was used for this purpose at Fraunhofer IST, supporting the modelling of gas flows and gas discharges in all system geometries with spatial and time resolution. In the course of developing the Megatron®, this for example made it possible to optimize the geometry and position of the apertures so that the two vacuum chambers for the different targets are separated as effectively as possible in terms of gas flow.
Advantage of the Megatron®
- Cost-effective process by increasing the coating rate
- Precipitation of material combinations that could not be produced before
- The composition of the primary target can be changed quickly through the use of the secondary target
- Improved coating characteristics through targeted doping, for example more homogeneous films
- Configurable stoichiometry through variable target composition
- Straightforward generation of gradient layers
- Highly precise processes through sputtering in Ar with subsequent oxidation
- Reduced development times
Applications for the technology
- Architectural glass coating
- Automotive glass
- Fine and precision optics
- Photovoltaic cells with improved efficiency