Test structure of different surface textures for reflection reduction in the scanning electron microscope
In many photometric applications, it is necessary to suppress stray light in the system as best as possible in order not to falsify the measurement results. Reflections on the surfaces of the detector elements used also influence the measurement results. For transmission or stray light measurements, directional back reflections of the detector in the direction of the target are especially critical, since the alignment of the detector can already cause errors in the interpretation of the measurement. For transmission measurements, the detector can be tilted so that the back reflection of the detector is not directed back to the sample. Directional back reflections are also problematic for scattered light measurements, since they can create scattered light paths and depend on the measurement setup. Repeated characteristic curve acquisitions and correction calculations are time-consuming and cost-intensive and also cannot eliminate all error influences.
The just started project “Photodiodes without back reflection” (PoRr) aims at the development of a largely reflection-free photodetector. To suppress directional reflection and thus enable more accurate photometric measurements, the CiS Research Institute is pursuing several approaches based on silicon 3D patterning methods. The aim is to explore the potential for manufacturability and operability, and in particular ways to overcome the limitations of existing photodiodes. The focus here is on miniaturized light traps and photosensitive coated surface structures.
The research and development work in the project “Photodiodes without back reflection” (PoRr) was funded by the German Federal Ministry for Economic Affairs and Energy.