SiM-TEC is a research center at the Fraunhofer Institute for Solar Energy Systems ISE that develops new technologies for the production of silicon wafers for photovoltaics and evaluates the materials used for this purpose. In the manufacturing of multicrystalline wafers, SiM-TEC’s work encompasses the evaluation of new feedstock materials, further development of the directional solidification of multicrystalline blocks, and the production of wafers based on sawing processes. In the kerfless wafering field, we investigate processes for the electrochemical porosification and deposition of silicon using atmospheric pressure epitaxy in a high-throughput process. We support all of these technology steps with numerous analytical options and simulation.
In order to minimize the entry of contaminants during multicrystalline wafer production, we are researching crucible systems and coatings of higher purity. Crystallization takes place as directional solidification using the vertical gradient freeze (VGF) process, with a focus on developing high quality wafers through processes with and without a seed crystal, as well as improving the material homogeneity and throughput by feeding silicon during crystallization.
Another technology focal point is developing the epitaxy of high-purity silicon material using CVD (chemical vapor disposition) in a continuous process. This is used for example for the growth of what is called an epitaxial wafer. We have an inline etching system for the electrochemical processing of Si wafers, which is able to carry out various full-surface (156x156 mm2) etching processes in multiple electrically isolated basins.