Programmable vapor-phase metal-assisted chemical etching for versatile high-aspect ratio silicon nanomanufacturing

Abstract

Defying the isotropic nature of traditional chemical etch, metal-assisted chemical etching (MacEtch) has allowed spatially defined anisotropic etching by using patterned metal catalyst films to locally enhance the etch rate of various semiconductors. Significant progress has been made on achieving unprecedented aspect ratio nanostructures using this facile approach, mostly in solution. However, the path to manufacturing scalability remains challenging because of the difficulties in controlling etch morphology (e.g., porosity and aggregation) and etch rate uniformity over a large area. Here, we report the first programmable vapor-phase MacEtch (VP-MacEtch) approach, with independent control of the etchant flow rates, injection and pulse time, and chamber pressure. In addition, another degree of freedom, light irradiation is integrated to allow photo-enhanced VP-MacEtch. Various silicon nanostructures are demonstrated with each of these parameters systematically varied synchronously or asynchronously, positioning MacEtch as a manufacturing technique for versatile arrays of three-dimensional silicon nanostructures. This work represents a critical step or a major milestone in the development of silicon MacEtch technology and also establishes the foundation for VP-MacEtch of compound semiconductors and related heterojunctions, for lasting impact on damage-free 3D electronic, photonic, quantum, and biomedical devices.

Layer-by-layer thinning of two-dimensional materials

“…Research in this direction will be of great importance. Moreover, new thinning techniques such as crystallographic thinning, [208][209][210][211] or metal-assisted chemical thinning, [212][213][214][215] are also well worth waiting for in the fabrication of thinned materials. However, for the applications of 2D material thinning, they need more time to demonstrate the exactness, and stability in the future and if successful, it could open routines for new thinning strategies with low cost and high quality.…”

Plasma‐Damage Free Efficiency Scaling of Micro‐LEDs by Metal‐Assisted Chemical Etching

“…In contrast, metal-assisted chemical etching (MacEtch) is a plasma-free, open-circuit anisotropic etching method that has been proven to produce high aspect ratio micro-and nanostructures in a variety of inorganic semiconductors, including Si, [18][19][20][21][22][23] Ge, [24] III-As, [25,26] III-P, [27,28] SiC, [29] 𝛽-Ga 2 O 3 , [30,31] and GaN. [32] MacEtch of III-N semiconductor materials involve three key components: illumination for photogeneration of carriers, metal catalyst for localized electronic charge separation, and etching solution typically consisting of an oxidant and an acid or base for chemical removal of the oxidized material.…”

Metal-Assisted Etching of n-Type and p-Type Silicon Using Patterned Platinum Films: Spatial Distribution of Mesoporous Layer and Open Circuit Potential of Silicon

“…11,12 Recently, metal-assisted etching in the HF vapor has also been reported. 13,14 The etching mechanism is commonly explained as follows. 1 The oxidizing agent is reduced on the metal catalysts and positive holes are injected into the valence band of Si.…”