Toward Controllable Wet Etching of Monocrystalline Silicon: Roles of Mechanically Driven Defects

Abstract

Wet chemical etching is essential not only for processing silicon (Si) wafers but also for forming diverse structures, significantly promoting the development of the semiconductor industry. However, tight control of etched topography at the nanoscale and even atom-scale in a controllable and reproducible fashion can be hardly achieved in either laboratory research or industrial production, seriously hindering further enhancement of high-performance Si-based electronic devices. Herein, the roles of mechanically driven defects in wet etching were systematically investigated toward promoting controllable wet etching of monocrystalline Si. The role of antietching of mechanically driven amorphous Si (a-Si) and the role of promoting etching of distorted Si (including dislocations and stacking faults) were revealed in anisotropic or isotropic etchants. It was also found that the nucleation of nanocrystals in the a-Si area with increasing contact pressure can lead to deactivation of the antietching mask, and the required contact pressure for deactivation in KOH and tetramethyl ammonium hydroxide solutions was much higher than that in HF/HNO3 mixtures. The selective etching mechanisms for every defect including a-Si, distorted Si, and nanocrystals were further addressed down to the atom-scale based on the proposed dissolution model. This study provides insights into deeply understanding the role of defects in wet etching and pushes forward the idea of controllable wet chemical etching in the Si-based semiconductor industry.

Lateral Bending of Ag Nanowires toward Controllable Manipulation

“…Figure a shows a separated NW on a Si (100) substrate selected for subsequent observation. Before focused ion beam (FIB) cutting, protective layers of polymer and Pt were deposited in turn to prevent the NW and the Si surface from being destroyed. , As seen from Figure b, grain boundaries were detected inside Ag NWs, which may cause relative displacement between the grains in each region when a load was applied from the outside. It was hence expected that the presence of grain boundaries can cause the crack generation in Ag NWs during the AFM indentation test or lateral bending.…”

Microreactor-based micro/nanomaterials: fabrication, advances, and outlook

“…Anisotropic wet etching is an important process for fabricating nanostructures that are widely used in silicon-based devices. 97,98 Tetramethyl ammonium hydroxide (TMAH) and potassium hydroxide (KOH) solutions are considered the most commonly used anisotropic etchants in the semiconductor industry. Hydrofluoric (HF) acid/nitric acid (HNO 3 ) mixtures are the most common isotropic etchant for silicon wafers and have been widely used to eliminate saw-damage and create MEMS structures, including deep holes and channels.…”

“…Anisotropic wet etching is an important process for fabricating nanostructures that are widely used in silicon-based devices. 97,98 Tetramethyl ammonium hydroxide (TMAH) and potassium hydroxide (KOH) solutions are considered the most commonly used anisotropic etchants in the semiconductor industry. Hydrofluoric (HF) acid/nitric acid (HNO 3 ) Fig.…”

Controlling amorphous silicon in scratching for fabricating high-performance micromixers

“…30 It was found that amorphous silicon (a-Si) generated in scratching can resist etching in acid or alkaline etchants, while other crystal defects including dislocations and lattice distortions can facilitate etching. 31 The sequential atomic arrangement of the Si lattice can be destroyed by scratching, forming superficial a-Si atoms with dangling bonds. The a-Si layer can cause an increase in the required energy for removing a-Si atoms in alkaline solutions.…”

“…In comparison, lattice distortions, e.g., dislocations and stacking faults, can widen the Si atom spacing and have more dangling bonds in {111} equivalent planes, facilitating the diffusion of reactive species to the reaction interface and thereby initiating the rapid replacement reaction of H groups by OH groups. 31 Accordingly, effective control of the scratching process, that is, the control of crystal damage generation, can ensure that post etching-induced channels are formed in the designed way.…”