Etching SiC‐slurry and diamond wire‐sawn silicon wafers with HF‐HCl‐Cl₂ mixtures: Parameter influences on etch rates and surface structures

Abstract

Solutions for the wet chemical treatment of silicon wafer surfaces were investigated using mixtures which are based on hydrofluoric acid (HF), hydrochloric acid (HCl), and chlorine (Cl 2 ). We used a DoE-test plan (Design of Experiments) to evaluate the effects of five selected parameters: concentrations of HF and HCl, gas flow rate of Cl 2 , stirring, and saw type of the wafer material. High etch rates of up to 0.63 mm min À1 were observed at room temperature, which are comparable to the etch rates of KOH-IPA solutions. The silicon surface was investigated by reflectivity measurements and scanning electron microscopy (SEM), indicating pyramidal textured and polished surfaces for diamond wireand SiC-slurry-sawn wafers. Using an optimized parameter set, random inverted pyramidal surface structures are formed. These random inverted structures show a significant increase in light absorption compared to standard random upright pyramid textures, for example produced by KOH-IPA solutions.

On The Mechanism of the Anisotropic Dissolution of Silicon in Chlorine Containing Hydrofluoric Acid Solutions

“…As also shown in previous works, anisotropic pyramidal 14 and inverted pyramidal 18,20 structures are generated on monocrystalline silicon (100) surfaces, when treating silicon wafers in HF-HCl mixtures with an added oxidizing agent. Figure 9 shows a SEM image of a silicon wafer surface after etching in an HF-HCl-Cl 2 mixture.…”