Anisotropic Wet Chemical Etching Research Articles

A Molecular Beam Epitaxy Approach to Quantum Dot Arrays

GaAs/AlAs quantum dot structures have been fabricated by atomic hydrogen-assisted molecular beam epitaxy (MBE). The substrates used were (111)B GaAs, on which tetrahedral-shaped pits surrounded by three equivalent triangular-shaped {111}A side facets have been produced by an anisotropic wet chemical etching. The deposition of GaAs on (111)A facets were decreased as a consequence of growth selectivity under atomic hydrogen irradiation. A high selectivity in the growth between on (111)B and (111)A has been uniquely utilized for the fabrication of quantum dot structures.

Fabrication of Novel Si Double-Barrier Structures and Their Characteristics

A novel Si (silicon)-based double-barrier structure (DBS) is newly proposed to study Si resonant tunneling devices. To form a thin Si single-crystal plate as a quantum well, anisotropic wet chemical etching and thermal oxidation are adopted. The DBS has a 43 nm-wide Si quantum well and 2.3 nm-thick SiO2 barriers. The electrical characteristic exhibits negative differential conductance (NDC).

Silicon micromachining for micro-replicationtechnologies

Silicon micromachining is applied to the fabrication of highly precise mould inserts to be used in the micro-replication of polymer waveguide components with integrated fibre alignment grooves. The waveguide structures with rectangular cross-section are realised by an anisotropic RIE process, whereas the integrated passive fibre alignment grooves are formed by anisotropic wet chemical etching. Two processes (a two-mask process and a selfaligned one-mask process) are described for the accurate alignment of waveguide structures and fibre alignment grooves.

Anisotropic Chemical Etching of Copper Foil: I . Electrochemical Studies in Acidic Solutions

Etching of thick copper foil masked except for a single rectangular opening having an aspect ratio (width:depth) of 5:1 or 1:1 was investigated in the presence of controlled laminar flow across the width of the pattern opening. In a solution of, copper was found to form a surface film spontaneously at the “corrosion potential,” to dissolve at a rate that depended upon convective mass‐transfer conditions, and also to exhibit anisotropic wet chemical etching. Based on thermodynamic calculations, it was estimated that the dominant cupric species were Cu+2, , , and , and that the dominant cuprous species was . Based on rotating disk measurements it was concluded that anisotropic chemical etching was related to the presence of a sparingly soluble surface film of . Under operating conditions for which anisotropic etching was observed, current transients were found to exhibit a characteristic “overshoot” response that may represent a useful diagnostic signal for process control.

Control of Si Solid Phase Nucleation by Surface Steps for High-Performance Thin-Film Transistors

The solid phase nucleation process of amorphous Si (a-Si) deposited by vacuum evaporation on thermally grown SiO2 layers on Si substrates having steps has been investigated. Steps were formed by either isotropic wet chemical etching of the SiO2 layer or anisotropic wet chemical etching of Si(100) followed by thermal oxidation. It has been found that solid phase nucleation is enhanced at the steps and that nucleation sites can be controlled by changing the step shape and a-Si thickness. Grain growth up to about 3 µm from the step edge has been observed. n-channel MOSFET's (metal-oxide-semiconductor field-effect-transistor's) which had steps at the source/drain edge were fabricated. They showed channel electron mobility of about 200 cm2/V·s, which is approximately one order higher than that obtained from MOSFET's fabricated in Si films formed by solid phase crystallization on flat SiO2/Si substrates.

Creation of 3D Patterns in Si by Focused Ga-Ion Beam and Anisotropic Wet Chemical Etching

ABSTRACTWe report the realization of free standing 3D structures as tall as ∼ 7μm with nano-scale thickness in Si using the technique of Ga focused ion beam implantation and sputtering followed by wet chemical etching. Some of the previously investigated subjects such as anisotropie etching behavior of crystalline Si and etch stop effect of Ga+implanted Si etched in certain anisotropie chemical etchants have been further explored with the emphasis on exploiting them in realizing free standing structures. The design and fabrication considerations in achieving such free standing structures are discussed and some typical structures fabricated by this technique are shown.

Fabrication of silicon field emission points for vacuum microelectronics by wet chemical etching

The fabrication of sharp silicon tips for field emission cathodes has been investigated using anisotropic and isotropic wet chemical etching techniques. Formulations of potassium hydroxide, water and alcohol are used as the anisotropic etchants. The effects of isopropyl, secondary butyl and tertiary butyl alcohols on tip formation are examined. An isotropic etchant using a mixture of hydrofluoric, nitro and acetic acids is also used to form similar cathode structures for comparison. The silicon needles formed are intended for use in vacuum microelectronic devices.

Thermal Activation of Crystalline Silicon Ions in Alkaline Solution

Anisotropic wet chemical etching of silicon in alkaline solutions (KOH) is one of the key techniques for the manufacture of microstructure. Fabrication of Micro-electro mechanical system (MEMS) part demand smooth surface finish and angular dependent etch rate. The absolute values of orientation dependent etch rate is found to vary with thermal agitation. In this work, experimental results of etch rate is found with their unusual values of activation energy along different planes. The various sites that an atom can occupy are not equivalent of their energy; some are more favorable to removal than others. In this paper attention is being given to demonstrate thermal activation is the prime factor that influences the behavior of etching mechanism as well as surface morphology. Atomic force microscopy (AFM) has been employed to analyze the morphology of the etched silicon surface at relevant elevated temperature. A systematic variation in morphological growth leads to stabilized surface structure under the influence of associated activation energy. Keywords: Activation energy; Etching; Anisotropy; Etch rate; MEMS; LPCVD; SOI. DOI: 10.3126/sw.v7i7.3817 Scientific World Vol.7(7) 2009 pp.15-18