Surface Texturing Behavior of Nano-Copper Particles under Copper-Assisted Chemical Etching with Various Copper Salts System

In this work, the effects of different copper salts on the etching behavior of n-type monocrystalline silicon wafers were detailedly studied. Firstly, the inverted pyramid, inverted pyramid-like and oval pit texturing structures were obtained by HF/H2O2/Cu(NO3)2, HF/H2O2/CuSO4 and HF/H2O2/CuCl2 etching systems. Then, the evolution process of copper nano-particles (Cu-NPs) deposition was studied to reveal the influencing mechanism of different anion species during the copper-assisted chemical etching (Cu-ACE) process. The textured wafer surfaces were characterized by scanning electron microscopy (SEM) and ultraviolet-visible (UVis) spectrophotometer, the etching rate, silicon wafer thinning and the deposition amount of Cu-NPs were systematically analyzed. The binding force between anion and cation species, the oxidation of anions and the formation of complex groups [CuCl2]− can greatly affect the deposition process of Cu-NPs, and resulting in different etching morphology and etching behavior. The moderate size and dispersive Cu-NPs in HF/H2O2/Cu(NO3)2 system leads to that the etching process is mild and the anisotropic etching ability can fully demonstrated. The regular inverted pyramid structures can be formed under low thinning of silicon wafers.