Modified Si Oxidation Behavior by Ultrathin Ni Catalyst Enabling Oxidant‐Less Metal‐Assisted Chemical Etching

Abstract Metal‐assisted chemical etching (MACE), a wet‐based anisotropic etching process for semiconductors, has emerged as an alternative to plasma‐based etching. However, using noble metal catalysts in MACE limits the implementation of complementary metal‐oxide‐semiconductor (CMOS) processes. This study explores Si etching using an ultrathin Ni catalyst as a novel approach for MACE. The thickness of the Ni catalyst emerges as a critical parameter, with 1 nm of Ni proving to be the optimal thickness to achieve smooth and deep etching. Unlike conventional MACE methods, the ultrathin Ni catalyst enables Si etching without strong oxidants. Wafer‐scale Si etching demonstrates the versatility of the ultrathin Ni catalyst in producing various microstructures. It is found that the ultrathin Ni/Si interfacial state plays a crucial role in influencing the Si reactivity, lowering the barrier for Si oxidation. CMOS‐compatible and cost‐efficient ultrathin Ni makes MACE a promising alternative for semiconductor nanofabrication. This study pioneers MACE using an ultrathin non‐noble metal catalyst, offering valuable insights for researchers in this field.