This article presents a study on Metal-Assisted Chemical Etching (MACE) of silicon in HF-H₂O₂ using silver nanoparticles as catalysts. Our aim is a better understanding of the process to elaborate new 3D submicrometric surface structures useful for light management. We investigated MACE over the whole range of silicon doping, i.e., p⁺⁺, p⁺, p, p⁻, n, n⁺, and n⁺⁺. We discovered that, instead of the well-defined and straight mesopores obtained in p and n-type silicon, in p⁺⁺ and n⁺⁺ silicon MACE leads to the formation of cone-shaped macropores filled with porous silicon. We account for the transition between these two pore-formation regimes (straight and cone-shaped pores) by modeling (at equilibrium and under polarization) the Ag/Si/electrolyte (HF) system. The model simulates the system as two nanodiodes in series. We show that delocalized MACE is explained by a large tunnel current contribution for the p-Si/Ag and n-Si/HF diodes under reverse polarization, which increases with the doping level and when the size of the nanocontacts (Ag, HF) decreases. By analogy with the results obtained on heavily doped silicon, we finally present a method to form size-controlled cone-shaped macropores in p silicon with silver nanoparticles. This shape, instead of the usual straight mesopores, is obtained by applying an external anodic polarization during MACE. Two methods are shown to be effective for the control of the macropore cone angle: one by adjusting the potential applied during MACE, the other by changing the H₂O₂ concentration. Under appropriate etching conditions, the obtained macropores exhibit optical properties (reflectivity ~3 %) similar to that of black silicon.

本文介绍了使用银纳米粒子作为催化剂对HF-H ₂ O _2中的硅进行金属辅助化学蚀刻（MACE）的研究。我们的目标是更好地理解制作可用于光管理的新3D亚微米表面结构的过程。我们调查MACE的整个范围硅掺杂，即，将P ⁺⁺，P ⁺，P，P ^-，N，N- ⁺和n ⁺⁺。我们发现，在p ⁺⁺和n ⁺⁺中，不是在p型和n型硅中获得了定义明确的直孔，硅MACE导致形成充满多孔硅的锥形大孔。我们通过对Ag / Si /电解质（HF）系统进行建模（在平衡和极化状态下）来说明这两个孔隙形成机制（直形和圆锥形孔隙）之间的过渡。该模型将系统模拟为两个串联的纳米二极管。我们表明，偏极化下p-Si / Ag和n-Si / HF二极管的隧道电流贡献很大，可以解释离域MACE，随着掺杂水平的提高以及纳米触点（Ag，HF）的减小，隧道电流的贡献增加。通过与在重掺杂硅上获得的结果进行类比，我们最终提出了一种使用银纳米颗粒在p硅中形成尺寸受控的锥形大孔的方法。这种形状，而不是通常的直中孔，通过在MACE期间施加外部阳极极化获得。已显示出两种方法可有效控制大孔锥角：一种是通过调节MACE期间施加的电势，另一种是通过改变H₂ O ₂浓度。在适当的蚀刻条件下，获得的大孔表现出与黑硅相似的光学性质（反射率〜3％）。