Etching Silicon with HF–HNO ₃ –H ₂ SO ₄ /H ₂ O Mixtures – Unprecedented Formation of Trifluorosilane, Hexafluorodisiloxane, and Si–F Surface Groups

The etching behaviour of sulfuric‐acid‐containing HF–HNO 3 solutions towards crystalline silicon surfaces has been studied over a wide range of H 2 SO 4 concentrations. For mixtures with low sulfuric acid concentration, NO 2 /N 2 O 4 , N 2 O 3 , NO and N 2 O have been detected by means of FTIR spectroscopy. Increasing concentrations of nitric acid lead to high etching rates and to an enhanced formation of NO 2 /N 2 O 4 . Different products were...