Wet‐Chemical Etching of Silicon Wafer Surfaces Using Aqueous HF‐HBrO ₃ and HF‐HBrO ₃ ‐Br ₂ Solutions

Abstract Solutions containing hydrofluoric acid (HF) and bromic acid (HBrO 3 ) are investigated as nitrogen oxide (NO x )‐free mixtures for wet‐chemical etching of (100) silicon wafer surfaces. Isotropic etching behavior with high dissolution rates of up to 10 µm min −1 is observed at room temperature, leading to polished surfaces. Anisotropic etching is observed when bromine (Br 2 ) is added to HF‐HBrO 3 solutions. Therefore, monocrystalline (100) silicon wafer surfaces are covered with random upright pyramids with edge lengths of about 5 µm. The etch rate is strongly dependent on the concentration of HBrO 3 . Silicon surfaces are analyzed by scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The gas phase is analyzed using Raman and infra red (IR) spectroscopy. The oxidation of the silicon surface by bromic acid likely takes place via oxygen insertion into the rearward silicon bonds. During etching, multiple active Br‐species are formed which alter the etching behavior.