Formation of Inverted Pyramid-Like Submicron Structures on Multicrystalline Silicon Using Nitric Acid as Oxidant in Metal Assisted Chemical Etching Process

H2O2 is predominantly used as an oxidizer in traditional metal assisted chemical etching (MACE), showing a high consumption rate due to its instability at room temperature. In this work, low concentration HNO3 instead of H2O2 is investigated in Ag-assisted chemical etching process for multicrystalline silicon (mc-Si) wafer. In comparative experiments, black silicon wafers with a surface reflection of 6.46% are obtained using HNO3 with only 5% molar concentration quantity of H2O2. After a post nanostructure rebuilding treatment, nano-scale inverted pyramid-like structures are obtained. SEM images reveal that increase in HNO3 concentration lead to an increase in surface roughness with enlarged structure size. Furthermore, a linear increase in etching rate is observed when AgNO3 concentration raised from 0 to 0.8 x 10(-3)m. The activation energy of 95.4 eV for the HNO3/HF-Si reaction catalyzed by Ag is obtained by Arrhenius equation. The outcomes demonstrate HNO3 as a potential alternative to conventional oxidizer H2O2 in traditional MACE process.