In order to reduce the ecological footprint and costs in the production of photovoltaic and semiconductor materials, scientists at the Institute of Inorganic Chemistry are conducting research into improving the wet-chemical treatment of wafer surfaces. Wafers for solar cell production and chip manufacture in the semiconductor industry are sawn from large silicon columns and therefore have a damaged, rough and contaminated surface. Wet chemical treatment helps to minimise this damage. This involves removing entire layers of silicon material. In further steps, it is possible to remove metallic and organic impurities through the treatment.

The aim of the research is to develop new types of processes that meet the requirements of the photovoltaic and semiconductor industry. In addition to a modified process control, this includes adapting the chemical composition of the etching solutions required for the treatment. Structures can be produced on silicon wafers that lead to higher light absorption in solar cells. This is currently achieved with mixtures of hot potassium hydroxide solution and organic additives. In the semiconductor industry, extremely clean and nanometre-smooth surfaces are required for chip production. To date, mixtures of nitric acid and hydrofluoric acid have been used for this purpose.

The institute is researching the dissolution behaviour of silicon in alternative etching media such as mixtures of hydrofluoric acid and chlorine for both applications. These work best at room temperature and do not generate any waste heat themselves, eliminating the need for cooling and heating. This reduces the energy requirement. And since hydrofluoric acid/chlorine mixtures already remove organic and metallic contaminants very well, the cleaning requirements for subsequent process steps are significantly lower. For application-ready tests, there are co-operations with German manufacturers of wet-chemical plants. Pilot plants are being constructed in joint projects. Even though initial results are available, basic research is still being conducted in this field to clarify chemical processes.