Direct Etching Research Articles

Nano-fabrication and Functionalization of Crosslinked PTFE Using Focused Ion Beam

It was demonstrated that the nano / microfabrication and functionalization for crosslinked Polytetrafluoroethylene (RX-PTFE) were carried out using focused ion beam (FIB). The fine pattern of the regularly nano-scale square array holes with 300 nm square size were fabricated by FIB direct etching. The fabricated samples were functionalized by post grafting reaction using trapped free radicals induced by FIB irradiation, and the samples were successively sulfonated. The obtained samples were treated by the mixture solution of KOH/KCl to make potassium form, and observed by FE-SEM with EDX spectroscopy. The signals correspond to potassium atom were detected at the holes in fabricated area of RX-PTFE. On the other hand, the signals of potassium formed sulfonic group were hardly detected at the distance of 10 μm from the hole's center in the fabricated area.

Direct etching of <inline-formula><math display="inline" overflow="scroll"><mrow><mi mathvariant="normal">Si</mi><msub><mi mathvariant="normal">O</mi><mn>2</mn></msub></mrow></math></inline-formula> and <inline-formula><math display="inline" overflow="scroll"><mrow><msub><mi mathvariant="normal">Al</mi><mn>2</mn></msub><msub><mi mathvariant="normal">O</mi><mn>3</mn></msub></mrow></math></inline-formula> by <inline-formula><math display="inline" overflow="scroll"><mrow><mn>900</mn><mtext>-</mtext><mi>keV</mi></mrow></math></inline-formula> gold ions

We report the direct etching of Al2O3 and SiO2 using 900-keV Au+ ions. 2000-mesh Cu grids were employed as masks using two different configurations: (1) the Cu mesh was placed on top of each insulator separately and independent irradiations were performed, and (2) the Al2O3 and SiO2 substrates were positioned in an edge-to-edge configuration with a single Cu grid providing a common mask to both insulators. Scanning electron microscopy (SEM) analysis revealed quite different patterns resulting from the two irradiation configurations. While the irradiation using individual masks resulted in mirror-image patterns of the Cu mask in the substrates, the use of a common mask led to single line structures approximately normal to the edges of the substrates. The role of charge buildup and sputtering in relation to relative dielectric properties of the substrates and close proximity of the samples during irradiation is discussed.

SR Direct Etching of PTFE and Its Application to Millimeter-Wave PTFE-Filled Waveguide

Microdevices have recently been developed by various micromachining technologies such as laser cutting, lithography, etc. PTFE is widely used as a microwave and millimeter-wave material. However, it is known that PTFE is too difficult to process with high precision by conventional machining, or even by laser cutting or electrical discharge machining. It has been reported that PTFE microstructures can be fabricated by direct exposure to synchrotron radiation. In this paper, the SR direct etching of PTFE is introduced and a trial fabrication of millimeter-wave PTFE-filled waveguide by sputter deposition of metal is attempted.

Fabrication of extreme-ultraviolet blazed gratings by use of direct argon-oxygen ion-beam etching through a rectangular photoresist mask

We present a simple method to fabricate blazed gratings used in the extreme-ultraviolet wavelength region. The method uses an argon and oxygen ion beam to etch directly the fused silica substrate through a rectangular profile photoresist grating mask. The blaze angle can be significantly reduced by using oxygen, and the profile evolution under ion-beam bombardment can be simplified when a rectangular mask is used. A simple geometric model is built to analyze the etching process. The etched grating groove profile is approximately triangular with a sharp apex angle provided the aspect ratio of the mask ridge is properly chosen; the blaze angle is directly proportional to the ion-beam grazing incident angle for a fixed oxygen partial pressure. Gratings of a 2400 line/mm groove density and 0.5-3 degrees blaze angles have been fabricated, which confirms the convenience of this method and the effectiveness of the etching model.

Numerical solving of the track wall equation in LR115 detectors etched in direct and reverse directions

Our equation of the track wall was solved numerically by using finite difference method and computer software MATHEMATICA. This method was applied for alpha particle tracks in LR115 detector, assuming both directions of etching, from the top and bottom of the sensitive layer. The equation of the track wall etched in reverse direction was derived, and has the same form as one for direct etching, with some difference in argument of V function. We will analyse the consequences of direct and reverse etching on the shape of alpha particles tracks with energies ranging from 2 to 4 MeV in thin LR115 NTDs.

Formation Mechanism of 100-nm-Scale Periodic Structures in Silicon Using Magnetic-Field-Assisted Anodization

We demonstrate highly directional etching in silicon 100 nm in diameter with an aspect ratio of 160 with no spiking on the pore walls using magnetic-field-assisted anodization. The relationship between the surface geometry of a silicon electrode and its highly directional etching properties have been investigated. Specifically, we show that the pore shape and pore wall orientation are not determined by the surface pattern but by the etching mechanisms specific to the magnetic-field-assisted anodization. These etching mechanisms enable highly directional and high aspect ratio etching at diameters below 100 nm in scale.

Patterning Properties of Indium–Tin Oxide Layer Depending on the Irradiation Conditions of Nd:YVO4 Laser Beam

A Q-switched Nd:YVO4 laser (λ= 1064 nm) with a galvanometric scanning system was used for the direct etching of an indium–tin oxide (ITO) film on a glass substrate. The etching properties of the ITO film depending on a pulse repetition rate were investigated. At a low pulse repetition rate of 10 kHz, the etching selectivity of ITO to soda-lime glass was poor, so that the glass substrate was also etched. In addition, the larger spot size formed at a lower repetition rate resulted in more severe ripples along the etched ITO line. In this experiment, it was shown that a pulse repetition rate higher than 40 kHz was adequate for the etching of an ITO film with a thickness of 1,200 Å on soda-lime glass. In particular, the larger spot size formed at the lower repetition rate resulted in more severe ripples along the etched ITO line. In our experiment, a 40 kHz repetition rate at a scanning speed of 500 mm/s was suitable for the formation of plasma display panel (PDP) bus electrodes.

Multi-level diffractive optical elements produced by excimer laser ablation of sol-gel

Material ablation by excimer laser micromachining is a promising approach for structuring sol-gel materials as we demonstrate in the present study. Using the well-known direct etching technique, the behaviour of different hybrid organic/inorganic self-made sol-gel materials is examined with a KrF* laser. Ablated depths ranging from 0.1 to 1.5 microm are obtained with a few laser pulses at low fluence (< 1 J/cm(2)). The aim is to rapidly transfer surface relief multi-level diffractive patterns in such a substrate, without intermediate steps. The combination with the 3D profilometry technique of coherence probe microscopy permits to analyse the etching process with the aim of producing multi-level Diffractive Optical Elements (DOE). Examples of four-level DOEs with 10 microm square elementary cells are presented, as well as their laser reconstructions in the infrared.

Glass Surface Analysis by an Optimized Sequential Chemical Etching Technique Using the Corrosive Agent HF/HNO&lt;sub&gt;3&lt;/sub&gt;

The characterization of the early reaction steps of the corrosion process in liquid media represents a tremendous challenge within the field of chemical analysis. In response to this, some known instrumental methods like AFM, SIMS and SNMS have proven themselves useful. Within the present work on the subject, we will introduce an optimized direct chemical etching technique which allows the quantification of the primary removed glass surface layers. It is based on the established etching procedure using hydrofluoric acid in combination with other mineral acids. The above mentioned method is modified and appropriately extended by enhancing the precision of the selected exposure time with the help of an automatic dipping device. Other improvements include the minimization of the dissolution rate by lowering the test temperature to – 10°C and also the decrease of the aqueous activity by adding alcohol instead of water into the acid solutions. Furthermore, by applying sequential etching with low concetrations of HF and HNO3, very small removal depths within the range below 10 nm per step are obtained. The equivalent components from the dissolved surface layers of the examined float glass are determined by subsequent chemical analysis of the etchants via AAS and ICP-OES. Their dissolution character can be well distinguished through a comparison between the gravimetric mass loss qgravim and the so-called normalized mass release per surface area qsol, calculated from the chemical composition of the corrosive solutions.

Fabrication and properties of Al 2O 3/Cu/InSnO 3 multilayer cathode electrodes in carbon nanotube field emission display

Multilayer cathode electrodes consisting of Al 2O 3 bufferlayer, Cu conductive layer and InSnO 3 current limiting layer, used in carbon nanotube (CNT) field emission display, were prepared by direct current magnetron sputtering and wet etching. Compared with conventional monolayer cathode electrodes, the multilayer electrodes possess higher current limiting resistance with lower inherent resistance variation. Profilometer measurement indicates the etched edges of the multilayer electrodes were abrupt and regular. Nano Indenter experiment shows that the multilayer electrodes remained intact after annealing treatment and were resistance to scratch damage at loads up to 12.6 mN. X-ray diffraction analysis reveals that no oxidized copper was formed during the annealing treatment. Atomic force microscope images show that the surface of the multilayer electrodes became smoother after plasma bombardment, and the maximum protrusion height decreased from 48.6 nm to 15.4 nm. With the multilayer cathode electrodes, the field emission properties of CNT film cathodes, such as uniformity, lifetime and stability are improved.

Fabrication of a PTFE-filled waveguide for millimeter-wave components using SR direct etching

PTFE is widely used as a microwave and millimeter-wave material. However, it is known that PTFE is a difficult material to cut at high precision by conventional machining, or even by laser cutting or electrical discharge machining. It has been reported that PTFE microstructures can be fabricated by direct exposure to synchrotron radiation. A metallic waveguide is one of effective media guiding a millimeter- and submillimeter-wave because of the advantage of low loss. In this paper, the SR direct etching of PTFE is introduced and a trial fabrication of millimeter-wave PTFE waveguide is attempted.

Design and fabrication of gold nanostructures with dispersed nanospheres for localized surface plasmon resonance applications

The design and fabrication of gold nanostructures through nanosphere lithography utilizing dispersed nanospheres, on glass substrate for the applications of localized surface plasmon resonance, were investigated in detail. The fabrication of the nanostructures was realized through the gold film deposition onto nanospheres dispersed on a substrate and the subsequent directional gold etching. Depending on the deposition and etching conditions of the gold, a variety of gold nanostructures can be fabricated. So far through this method, only 2D nanocrescents had been reported. However, either 2D or 3D non-conformal nanostructures are formed in this way, and the profiles of the obtainable nanostructures were simulated under various conditions. For nanostructures fabricated on glass, the simulated profiles coincided well with the fabricated ones. These results prove that our profile simulation program can realize the design of 2D and 3D nanostructures obtainable by dispersed nanospheres, and reduce the effort and cost for achieving desired nanostructures by experiments in the trial-and-error stage.

Catalysis of dispersed silver particles on directional etching of silicon

Silver particles are dispersed on silicon by magnetron sputtering and post-annealing to investigate the catalytic effects of individual silver particles on wet etching of silicon surface. According to scanning electron microscopy, dispersed deep holes are present and the major etching direction is vertical to the surface of a Si(1 0 0) wafer or inclined to that on a Si(1 1 1) wafer. Our experiments indicate that the effect of the anisotropy of Si on directional etching is fundamental and the wafer resistivity and experimental process have important influence on the etching results. In addition, aggregation of silver particles and random horizontal etching on the surface of the wafer are caused by the local imbalance between the oxidant and HF. Our results enable better understanding of the catalytic effects of metal particles on silicon and are helpful to the preparation new silicon nanostructures.

Micro-machinability of monocrystal silicon by direct etching using excimer laser

The high flexibility of laser direct writing and its potential capability of fabricating micro-mechanical structure are discussed. Aiming at providing knowledge for micro-engineering application, experiments on direct etching of monocrystal silicon with focusing KrF excimer laser beam (λ = 248 nm) were carried out. The validity of non-thermal excimer laser material processing was examined by SEM observation on the “heat-affected zone (HAZ)”. An empirical formula establishing the relationship of etching depth versus laser energy per pulse and the number of laser pulses has been derived from the experiments. Impact damage at the underside of silicon wafer has been observed. Its relevant causes are analyzed.

Texture Etching of Si with Atomic Hydrogen Generated by Hot Wire Method through SiO2 Masks for Solar Cell Applications

Texture etching of (100) and (111) single-crystal silicon using atomic hydrogen generated by the hot wire method was examined both by direct etching and etching through masks formed from SiO2 particles. Etching with SiO2 masks formed from colloidal silica solution produced a crater like texture on both oriented substrates. It was also found that the thickness of the mask region can be adjusted by changing the concentration of colloidal silica and by mixing different sizes of silica particles. The reflectivities of the substrates with textures generated by optimized mask formation were found to reach minima of about 13% for Si(100) and 19% for Si(111), which were lower than those of multicryastalline substrates with textures generated by alkali etching.

Effects of leakage current and Schottky-like ohmic contact on the characterization of Al 0.17Ga 0.83N/GaN HBTs

This work investigates the effect of non-ideal material and contact conditions on the characterization of Al 0.17Ga 0.83N/GaN heterojunction bipolar transistors (HBTs) by comparing numerical simulations with measured device characteristics. Al 0.17Ga 0.83N/GaN HBTs are grown by metalorganic chemical vapor deposition and fabricated by direct mesa dry etching. From measured Gummel plot, anomalously high current gain is observed at low current level and then decreases to 2459 at collector current of 1 mA. The common-emitter output characteristics demonstrate dc current gain of 1.22. The inclusion of base–collector and collector–emitter leakage currents with Schottky-like Ohmic contacts in simulation enables good agreement with measured Gummel plots and common-emitter output currents, and shows that leakage current at the base–collector junction is the major source of the non-ideality in device characteristics. Finally, the characteristic of the intrinsic Al 0.17Ga 0.83N/GaN HBT is presented.

Focused-Ion-Beam Fabrication of Slanted Grating Couplers in Silicon-on-Insulator Waveguides

We have designed and fabricated an efficient grating coupler for coupling light between optical fibers and silicon-on-insulator waveguides. The coupler consists of 88-nm-wide slits, etched at an angle of 58deg to the surface normal. They are defined by direct etching with a focused ion beam, using iodine gas and an alumina hard mask. The measured efficiency is 46%

Fabrication and surface functionalization of high aspect ratio plastic nanostructures

Soft UV nanoimprint lithography and reactive ion etch techniques have been used to pattern high density and high aspect ratio nanostructures on the surface of a plastic plate such as Plexiglas. A thin film of photo-curable resist is first spin coated on the plastic plate, with or without deposition of a 10 nm thick germanium intermediate layer. Then, a soft stamp made of poly-dimethylsiloxane (PDMS) is used to mold the photo-curable resist, followed by a UV light exposure. Finally, the imprinted pattern is used as mask for a sequential reactive ion etch of the residual resist layer, the intermediate layer if any, and the plastic plate. Such a soft nanoimprint and direct etch technique allowed us to obtain high density nanostructures with an aspect ratio up to 15. To demonstrate the applicability of such systems in biology, wetting behaviours and surface functionalization with fluorescent protein molecules have been studied. We believe that this low cost approach is high throughput and efficient for a number of applications.

New Design Concept and Fabrication Process for Three-Dimensional Silicon Photonic Crystal Structures

We propose a new design concept and a fabrication process for three-dimensional (3D) silicon photonic crystals on a 100 nm scale that does not require any alignment processes. The elemental technique used in this process is two directional electrochemical etching processes at a particular magnetic field. First, we have performed photonic band calculation and estimated device parameters to obtain the maximum photonic band gap in the visible range centered at around 800 nm. Next, we have experimentally observed the formation of a two-dimensional periodic pore with a diameter of 80 nm and an aspect ratio above 80 on an n+ (100) silicon substrate. Finally, we have fabricated 3D microstructures by two directional etching processes. A clear directionality for the pore formation was observed in two directions, showing the possibility of projecting the patterns formed on the slope to the side of the wafer. These fundamental etching processes can be applied to the fabrication of 3D photonic crystals in the visible range without any alignment processes.

Direct photonic etching of electrical materials

Multiwavelength Diode Pumped Solid State (DPSS) lasers allows operations such as micromachining in a variety of materials such as ceramics, metals and polymers. A series of experiments was performed to investigate how the protective gas environment and gas pressure affect the ability to cut and machine silicon steel. Results from this study reveal that traditional plasma-controlling gases have a detrimental effect on the surface morphology of machined electrical components. This paper discusses the theory behind direct photonic etching and explains how the machining of thin plates of silicon steel can benefit the rapid production of electrical components such as transformer cores and dynamo pole pieces.