Texturing of SiC-slurry and diamond wire sawn silicon wafers by HF–HNO3–H2SO4 mixtures

• The etching behavior of SiC-slurry and diamond-wire sawn silicon wafers is studied.
• H2SO4-rich HF–HNO3–H2SO4 mixtures generate surface textures on both wafer types.
• Texturing in H2SO4-rich mixtures raises the roughness of silicon wafers.
• Texturing in H2SO4-rich mixtures reduces the reflectivity of silicon wafers.
• Solar cells textured by H2SO4-rich mixtures exhibit increased cell efficiencies.

The reactivity of HF(40 wt%)–HNO3(100 wt%)–H2SO4(97 wt%) etching mixtures towards conventional SiC-slurry and diamond-wire sawn silicon wafers has been studied. Sulfuric acid-rich mixtures exhibit adequate etching rates (r<5 µm min−1) and generate homogenously distributed, small etching pits on both types of silicon wafers. Textured wafer surfaces were characterized by means of scanning electron microscopy (SEM), laser scanning microscopy (LSM), surface roughness analyses and reflectivity studies. The surface roughness is influenced by the etch depth and the type of saw damage. Etching in sulfuric acid-rich mixtures significantly reduces the reflection of SiC-slurry sawn wafers and, in particular, of diamond-wire sawn wafers. The reflection of etched silicon surfaces is discussed in terms of etch depth and surface roughness. Compared to the conventional HF–HNO3–H2O etching process, multicrystalline silicon (SiC-slurry and diamond-wire sawn) based solar cells texturized by sulfuric acid-rich mixtures exhibit increased efficiencies.