Optimized Hole Injection, Diffusion, and Consumption for Efficient Metal-Assisted Chemical Etching Depending on the Silicon Doping Type and Metal Catalyst Area

Even though metal-assisted chemical etching (MACE) has been widely used for silicon (Si) nano/micromachining due to its low cost and high applicability, it is still difficult to fabricate elaborate Si nano/microstructures for high-value applications. In particular, further studies about effective factors in the MACE process with systematic approaches are highly required to obtain explicitly controlled MACE products. In this study, how the Si doping type and gold (Au) catalyst area influence MACE products in terms of the hole behavior during MACE is investigated. The type-dependent etching rate of MACE, amount of reaction products, and lateral etching/porosity of the MACE product are characterized with hole injection, diffusion, and consumption scenarios, respectively. Moreover, it is demonstrated that the dependence of the etching rate of MACE and stability/porosity of the MACE product on the Au catalyst area can be understood from the point of view of hole injection per interfacial contact plane area of the Au catalysts. As a result, elaborately controlled Si nano/microstructures can be obtained through an effective and accurate MACE process due to the optimized hole behavior. These findings could increase the accessibility and commercial availability of MACE products in many fields.