Dennis Barton, Philipp Henning, Chris Britze, Thomas Melzig, Michael Vergöhl, Fraunhofer Institute for Surface Engineering and Thin Films IST, Braunschweig, Germany
These days, the digital twin has become more and more an usual partner to his real brother. The in silico execution of coating runs has already shown the great potential to accelerate development processes in all terms of technology, economics, and ecology.
But still, the real twin gets born much earlier than his digital counterpart. In the history of research and engineering, the a posteriori approach, i.e., build first-tweak later, this was the only way of doing things due to the lack of computational power and specialized software. However, most of the great invention of mankind has been invented this way.
Being just of bits and bytes, the simulated model can be adapted fast and cheap. Therefore, processes and coater designs can be tested before implementation. Once, the implementation is done, design faults – plasma leaks, gas separation issues, inhomogeneous coatings, etc. – are much costlier to improve.
At the IST, the in house code PICMC is applied to simulate and optimize CVD and PVD processes. Based on a digital representation of the coater in question, we simulate the plasma and gas fluxes. On this basis, further properties are derived, e.g., target erosion layer thickness profile, etc.
An example for the full benefit of this simulation framework is the EOSS^© platform. Here, we are able to apply a manifold of optical filter designs on lenses of different shapes, e.g., a bandpass on a spherical lens, anti-reflex on an aspheres, etc.
To account for the large variety of possible settings, shaper masks are used. To adapt new designs, a trail-and-error approach to the shaper form is just not feasible. Therefore, we apply a chain of plasma simulations, gas flux/sputter particle modeling, ray-tracing based layer thickness prediction and – in the end – fitting algorithms. This yields an optimal shaper geometry in a few minutes, which can directly be build and implemented in the coater.