Uniform trench arrays with controllable tilted profiles using metal-assisted chemical etching

Silicon (Si) micro-trenches with large-area uniformity and tunable taped sidewalls were prepared using a metal-assisted chemical etching (MaCE) process. Systematical investigations on both dynamics and influences of HF/H ₂ O ₂ electrolytes for the etching of Si patterned with Au catalysts were performed. With the increased introduction of HF in catalytic etching, both the etched depths and profiles are dramatically altered, where the resulting trench angles, defined as the angles between the taped sidewalls and bottom regions of trenches, are explicitly modulated within the region of 45°-88°. These findings can be attributed to the unequal etching rates, which take place at edge and the rest of clustered Au catalysts and then break the continuity of Au catalysts at edge gradually as etching process proceeds, eventually leaving the taped profiles of Si trenches. By applying such unique angle-modulated characteristics revealed in this work, the innovative designs of multiple-taped trenches are further demonstrated, which may further pave ways for realizing the three-dimensional complex architectures.