Stepwise dual-Cu-salt etching for high-uniformity inverted pyramid texturization: Anion-mediated regulation

Abstract

In this work, we proposed a stepwise dual-Cu-salt etching system for metal-assisted chemical etching (MACE) to achieve highly uniform inverted pyramid textures on silicon surfaces. Through comparative analysis of Cu(NO₃)₂-assisted chemical etching (ACE) and CuSO₄-ACE systems, we identified a critical trade-off: Cu(NO₃)₂-ACE produced non-uniform morphologies due to hindered copper nanoparticle deposition, while CuSO₄-ACE produced homogeneous yet shallow inverted pyramid structures. Based on mechanistic analysis of the underlying chemical reactions, we resolved this conflict through a stepwise method including initial uniform nucleation points with subsequent deep vertical etching. Consequently, the texturing structures obtained via stepwise dual-Cu-salt etching exhibited superior uniformity, enhanced light-trapping capability, and reduced surface reflectance.