Create High-Aspect-Ratio Silicon Nanostructures Using Metal-Assisted Chemical Etching (MACE) Technique

Silicon nanostructures are one of the candidates for tomorrow technologies due to its novel physical properties. High-aspect-ratio silicon nanostructures have been proved as effective microstructures for enhance silicon solar cells efficiency. Silicon nanowires enhance solar cells efficiency by formation vertical well aligned nanowires on the top surfaces which give effects to the optical, electronic and physical properties of silicon solar cells. Silicon nanowires also can enhance the carrier collection of photovoltaic devices. There are two types of methods used to fabricate silicon nanowires such as top-down or bottom-up fabrication. One of the techniques to get high-aspect-ratio nanostructures is by using metal-assisted chemical etching (MACE). Metal-assisted chemical etching (MACE) technique has been adopted in many research experiments and technology due to its low cost fabrication of silicon nanowires but can form a high-aspect-ratio of silicon nanowires. MACE has demonstrates outstanding results of silicon nanowires in improving many microelectronics and photonic devices. Traditionally, MACE is operated by making a holes using metal catalyst in order to reduce of using the etchant. The mobility of the reactants impeded when the height of silicon nanowires increases which resulting insufficient holes. However, MACE also has advantages and drawbacks which appear such as long-vertical-well aligned silicon nanowires and some broken silicon nanowires due to very thin silicon nanowires which easily to break, respectively. In this paper, different solutions concentration is study using a two-step MACE process. The chemical solution contains HF/AgNO
3
and also H
2
O
2
. The experiment is conducted at room temperature. During the etching process, anisotropic growth different silver particles which used for the formation of the silicon nanowires on silicon wafer surfaces. As a results, the etch rate gives the effect on the silicon nanowires length. A comparative study of etch rate has been conducted in order to see clearly the differences.