Wafer-level integration of self-aligned high aspect ratio silicon 3D structures using the MACE method with Au, Pd, Pt, Cu, and Ir

Abstract

The wafer-level integration of high aspect ratio silicon nanostructures is an essential part of the fabrication of nanodevices. Metal-assisted chemical etching (MACE) is a promising low-cost and high-volume technique for the generation of vertically aligned silicon nanowires. Noble metal nanoparticles were used to locally etch the silicon substrate. This work demonstrates a bottom-up self-assembly approach for noble metal nanoparticle formation and the subsequent silicon wet etching. The macroscopic wafer patterning has been done by using a poly(methyl methacrylate) masking layer. Different metals (Au, Pt, Pd, Cu, and Ir) were investigated to derive a set of technologies as platform for specific applications. Especially, the shape of the 3D structures and the resulting reflectance have been investigated. The Si nanostructures fabricated using Au nanoparticles show a perfect light absorption with a reflectance below 0.3%. The demonstrated technology can be integrated into common fabrication processes for microelectromechanical systems.

Silicon Nanostructures for Molecular Sensing: A Review

“…83−89 Figure 5 shows the scheme of SiNWs synthesis by MACE with a silver metal salt. 90 The morphology of SiNWs could be altered by tuning several etching parameters such as nature of the metal catalyst, etching time, etching temperature, concentration of oxidation (H 2 O 2 ), etching (HF) agents, and intrinsic properties of silicon (e.g., orientation, doping type, doping level). 91,92,46 In a pioneering work, the review by Toor et al 93 correlation of etching parameters on the resultant SiNWs.…”

“…Recently, a review by Leonardi et al has extensively discussed all the conventional techniques and investigated their possibilities in the commercial transfer of technology in microelectronics and optoelectronics in a single chip by counting the stability, cost, reproducibility, and complexity in the synthesis . The MACE mechanism involves a charge transfer process between a metal catalyst and silicon, which necessitates the oxidation and dissolution of Si. − Figure shows the scheme of SiNWs synthesis by MACE with a silver metal salt . The morphology of SiNWs could be altered by tuning several etching parameters such as nature of the metal catalyst, etching time, etching temperature, concentration of oxidation (H 2 O 2 ), etching (HF) agents, and intrinsic properties of silicon (e.g., orientation, doping type, doping level). ,, In a pioneering work, the review by Toor et al demonstrated a direct correlation of etching parameters on the resultant SiNWs.…”

CoO, Cu, and Ag Nanoparticles on Silicon Nanowires with Photocatalytic Activity for the Degradation of Dyes

“…Some etching mechanisms have been proposed to explain the MACE process. A reduction reaction for the cathodic process implies the decomposition of H 2 O 2 at the metallic surface in acidic conditions [46][47][48][49][50].…”

“…In this process, the silicon is oxidized to SiO 2 and SiF 2− 6 . The holes h + generated are consumed by the silicon substrate and the anodic process occurring under the metallic deposited silver could be described as follows [46,47,50,52]:…”

“…In addition, if n = 2, there is a ratio of 1:1 between the etched silicon and one molecule of H 2 formed. While the former mechanism is associated with the silicon/metal interface producing a straight etched profile, the latter can occur outside the interface and allows obtaining nanoporous silicon [47].…”