Texturisation of Multicrystalline DWS Wafers by HF/HNO3/H2SO4 at Elevated Temperature

The acidic texturization of multicrystalline silicon diamond wire sawn wafers (mc-Si DWS) with smooth surfaces has been a challenge for years. One possibility to texture smooth surfaces is a solution consisting of hydrofluoric acid, nitric acid and sulfuric acid (HF/HNO3/H2SO4). The favored texturing behavior of this solution instead of HF/HNO3 might be due to the high viscosity and an enhanced NOx+ generation due to the sulfuric acid. As the HF/HNO3/H2SO4 texturing process showed a decreasing reflection with increasing temperature, the temperature and time dependence of the etch depth and reflection has been evaluated. At temperatures above 45°C a texture with total reflection values of 22% at 600 nm was achieved at 15 µm total etch depth and a structure height of 2 µm in 60 s. The textured surface might be due to gas phase etching in the generated gas bubbles. This result poses a promising starting point for finding an adequate additive for the mc DWS texturing process.