Surface Texturing Behavior of Nano-copper Particles under Various Copper Salts System during Copper-assisted Chemical Etching

Abstract

In this work, the effects of different copper salts on the etching behavior of n-type monocrystalline silicon wafers were detailedly studied by Cu-assisted chemical etching method. 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 of copper particles deposition behavior was studied to reveal the influencing mechanism of different anion species, the textured wafer surfaces were characterized by scanning electron microscopy (SEM) and ultraviolet-visible (UV) spectrophotometer, the etching rate, silicon wafer thinning and the deposition amount of copper particle was systematically analyzed. We conclude that the binding force between anion and cation, the oxidation of anions and the formation of complex groups [CuCl2]− lead to great difference in the deposition behavior of copper, resulting in different etching morphology and etching rate. The moderate size copper particles deposited from HF/H2O2/Cu(NO3)2 system make that the etching process is mild and the anisotropic etching ability can fully demonstrated, and the regular inverted pyramid structures can be formed under low thinning of silicon wafers. This work will provide guidance for controllable preparation of inverted pyramid structure and future application in high efficiency solar cells.