Detection of Photoelectrons Emitted from Wet-Processed Si Trench Bottoms

The goal of this study is to characterize the surface condition of Si trench bottoms using X-ray photoelectron spectroscopy (XPS). Si trenches were fabricated by metal-assisted chemical etching (MACE) with thin Au stripes embedded at the trench bottoms. After verifying the characteristic photoemission behavior of the embedded Au, the Au was selectively removed, and the Si 2p spectra were analyzed. A distinct spectral component appeared in the Au-removed samples, attributable to the exposed Si surface at the trench bottoms. This finding demonstrates that photoelectrons emitted vertically from the trench bottoms can be spectroscopically distinguished from those originating from other regions, such as the trench top surface. The underlying mechanism is associated with the MACE process and subsequent HF treatment, which preserve a crystalline Si surface at the trench bottoms while forming a thin porous layer elsewhere. These results open new opportunities for understanding local surface chemistry and electronic structure within three-dimensional Si architectures, providing new insights into solution/Si interfacial interactions.