Type Of Etchant Research Articles

Level set implementation for the simulation of anisotropic etching: application to complex MEMS micromachining

The use of atomistic methods, such as the continuous cellular automaton (CCA), is currently regarded as an accurate and efficient approach for the simulation of anisotropic etching in the development of micro-electro-mechanical systems (MEMS). However, whenever the targeted etching condition is modified (e.g. by changing the substrate material, etchant type, concentration and/or temperature) this approach requires performing a time-consuming recalibration of the full set of internal atomistic rates defined within the method. Based on the level set (LS) approach as an alternative and using the experimental data directly as input, we present a fully operational simulator that exhibits similar accuracy to the latest CCA models. The proposed simulator is tested by describing a wide range of silicon and quartz MEMS structures obtained in different etchants through complex processes, including double-sided etching as well as different mask patterns during different etching steps and/or simultaneous masking materials on different regions of the substrate. The results demonstrate that the LS method is able to simulate anisotropic etching for complex MEMS processes with similar computational times and accuracy as the atomistic models.

The Influence of Various Etchants on the Quantitative Analysis of Microstructure of Mg-Nd Alloy

The paper presents the results of the influence of various etchants on the quantitative analysis of microstructure of Mg-Nd master alloy. The methodology of quantitative analysis of these alloys’ microstructure were also presented. Qualitative analysis were done using light and scanning electron microscopes, chemical composition was investigated using EDS method. Seven types of etchants were used. Having chosen suitable images, quantitative analysis were done using Met-Ilo program. Comparison of results showed that chosen etchants didn’t make the significant influence on the quantitative analysis results of the microstructure, despite visible dissimilarities.

Surface Preparation of 4° Off-Axis 4H-SiC Substrate for Epitaxial Growth

Results of surface preparation on Si-face 4° off-cut 4H-SiC substrates are presented in this paper. The influences of two types of etchants, i.e. hydrogen chloride (HCl) and only hydrogen (H2), were investigated by Nomarski microscopy and AFM. The experiments were performed in a hot wall CVD reactor using a TaC coated susceptor. Four etching temperatures, including 1580 °C, 1600 °C, 1620 °C and 1640 °C, were studied. In-situ etching with only H2 as ambient atmosphere is found to be the optimal way for the SiC surface preparation. Using HCl at temperature higher than 1620 °C could degrade the substrates surface quality.

Influence of Etchants on Quantitative/Qualitative Evaluations of the γ′ Precipitates in a Nickel-Base Superalloy

To evaluate the microstructural characteristics of nickel-base superalloys, the size, number density, volume fraction, and morphology of the γ′ precipitates are frequently analyzed. For accurate microstructural analysis, a proper etching treatment should be applied evenly over the sample. Lack of care in choosing either the etchant or the etching technique can result in significant errors, not only in qualitative observations but also in quantitative analysis of the γ′ precipitates. This research examined the effects of etching technique as well as etchant type on the microstructural characterization of the γ′ precipitates in IN738LC nickel-base superalloy. The heat-treated samples with the same morphology of the γ′ precipitates were independently etched either in matrix phase (γ) or in γ′ precipitate etchants. After quantitative analysis by scanning electron microscopy, the results were compared with electrolytically extracted γ′ precipitates for the same samples. The results show clearly that for qualitative and morphological observations of the γ′ precipitates, the matrix phase γ etchants are desirable, while for quantitative analysis, the γ′ etchants can provide appropriate results.

Crystalline Te nanotube and Te nanorods-on-CdTe nanotube arrays on ITO via a ZnO nanorod templating-reaction

Vertically aligned Te nanotube and CdTe nanotube arrays branched with Te nanorods were demonstrated on an indium tin oxide (ITO) substrate via a ZnO nanorods templating-reaction method. By simply changing the etchant type and etching temperature of the ZnO–CdTe core–shell nanocables, the ZnO cores can be selectively etched off and the chemical reaction from CdTe to Te can be well controlled to form pure CdTe or Te nanotubes, or Te nanorods-on-CdTe nanotube nanocomposite arrays. Both the well-crystallized Te nanotubes and the Te nanorods are of hexagonal phase, of which the former have respective wall thickness, diameter and length of ∼60 nm, ∼150 nm and ∼8 μm, and the latter have diameter and length of ∼17 nm and ∼80 nm. Dynamic studies on the structural and morphological evolution from ZnO–CdTe nanocables to the Te-related nanostructures were performed. The formation mechanism of the Te nanorods-on-CdTe nanotube arrays and pure Te and/or CdTe nanotube arrays are discussed.

Morphological classification and quantitative analysis of etch pits

Etch pits created by hydrochloric and phosphoric acid on cleaved CaF2(111) are investigated by scanning force microscopy (SFM). A geometric and dimensional analysis of the etch pits reveals two distinctly different types. Type-I etch pits evolve at dislocation defects, are pointed and their size and eccentricity is related to the angle between the dislocation and the surface. Type-II etch pits result from defects below the surface, are flat-bottomed for longer etching times and exhibit a characteristic ratio of depth and edge length depending on the type of etchant. An analysis of etch pit morphology allows an identification of the origin of an etch pit and a characterization of the associated defect structure.

Effects of blood and saliva contamination on shear bond strength of metal orthodontic brackets and evaluating certain methods for reversing the effect of contamination

The background and purposeContaminations may reduce shear bond strength (SBS) of orthodontic brackets. For reversing such effects, certain surface treatments are suggested. This study was conducted to evaluate (1) effects of saliva and blood contamination on SBS of metal brackets, (2) the efficacy of three surface treatments, while (3) using two adhesives (37% phosphoric acid etchant (Ivoclar/Vivadent)+RMGIC (Fuji Ortho LC), and self-etchant primer (iBonD GI)+composite resin (No-Mix, Dentaurum)). MethodsThe sample was categorized into 12 experimental subgroups (2 contaminations×3 treatments×2 adhesives, n=12×10) and 2 control subgroups (n=2×10). Experimental specimens underwent different treatments according to their group. They were incubated (37°C, 96h) and thermocycled (3000 cycles, 5–55°C, dwell time=30s). SBS was tested at 1mm/min crosshead speed. ResultsSEP–composite produced significantly lower SBS rates (P<0.05) according to Mann–Whitney. ANOVA indicated a significant difference between blood contamination and both control and saliva contamination. According to Wilcoxon signed rank test, comparing with SBS=7, drying failed to achieve appropriate SBS rates (except drying saliva when using RMGIC). On RMGIC, re-etching and rinsing–drying methods might provide sufficient SBS levels. All treatments (except rinsing–drying saliva contamination) did not produce appropriate SBS levels when using SEP–composite. ConclusionsBlood contamination reduced the SBS much greater than saliva. Using etchant–RMGIC is strongly recommended. Drying may only suffice when RMGIC is used over saliva contamination. The efficacy of re-etching depends on the etchant type. Rinsing–drying may produce appropriate SBS levels.

The effect of acid etchant type and dentin location on tubular density and dimension

Coronal and radicular dentin may react differently to the type of acid treatment used when bonding to these substrates. The purpose of this study was to characterize and compare dentin morphology, tubular density, and cross-sectional area in deep coronal (around an exposed pulp horn) and root canal dentin at the cervical third in the intact state and after acid etching with phosphoric acid or self-etching dentin primer. Extracted, human, caries-free premolars were fixed. Smear layer-free sections (control) were obtained and divided into 3 groups: left intact, etched with phosphoric acid, or etched with a self-etching primer from a dentin bonding system. Specimens were examined using scanning electron microscopy. Tubular density and cross-sectional area were determined from the images using software. Values were submitted to multifactorial ANOVA (alpha=.05). Tubular density was not significantly affected by acid type or by dentin location. Acid type significantly (P<.001) affected tubular cross-sectional area: phosphoric acid > self-etching resin > intact dentin, irrespective of dentin location. All acid-treated specimens showed demineralization, and irregular surface morphology was not affected by either acid treatment. Tubular density was not significantly different between deep coronal and root canal dentin nor affected by acid treatment type. Tubular cross-sectional area did not differ between deep coronal or root canal dentin, regardless of acid treatment. Both acid types significantly increased tubular cross-sectional area at both dentin locations, phosphoric acid to a greater degree than the self-etching primer. Root canal dentin did not display peritubular dentin.

Some features of a microdefect revealing in single-crystal silicon by the preferential etching technique

Abstract Poorly known features of a microdefect (MD) delineation in dislocation-free single-crystal silicon by the defect-contrast (DC) etching technique were studied experimentally using DC-solutions of the HF–CrO 3 –H 2 O and HF–K 2 Cr 2 O 7 –H 2 O systems. The dependences of shape and size of an individual MD-trace on the etchant type, etch time (etch depth), and microdefect type have been demonstrated. Taking into account of these dependences allows one to improve selectivity and sensitivity of the technique. Compositions of the most effective DC-etchants were noted.

Various shapes of silicon freestanding microfluidic channels and microstructures in one-step lithography

In this research, we have developed and demonstrated a fabrication method for the formation of various shapes of silicon freestanding microfluidic channels and microstructures in one-step photolithography. The fabrication process utilizes the silicon direct wafer bonding with silicon nitride as an intermediate layer, local oxidation of the silicon (LOCOS) process and wet anisotropic etching. Two different types of etchants (non-ionic surfactant (Triton-X-100) added and pure 25 wt% TMAH solutions) are used in series to perform silicon anisotropic etching. Surfactant-added tetramethyl ammonium hydroxide (TMAH) is employed to define the shapes of the structures, while pure TMAH is used to get high undercutting for their fast releasing. The non-ionic surfactant is preferred considering the complementary metal-oxide semiconductor (CMOS) post process issue of wet anisotropic etching. The undercutting at sharp and rounded concave corners, edges aligned along ⟨1 0 0⟩ directions, is measured and analyzed in both pure and surfactant-added TMAH solutions. Mask design issues that must be taken into consideration for the fabrication of desired shape and size structures are also presented.

Local Laser Oxidation of Thin Metal Films: Ultra-resolution in Theory and in Practice

Laser–induced oxidation on thin metallic films with following selective etching is a powerful method for micropatterning of different structures like photomasks, diffractive optical elements etc.Nowadays the most interesting question is how small could be structures produced by this tech-nology, what are theoretical limitations and where is a practical limit for that? Under this research will be shown that Arrhenius dependence of oxidation speed from temperature raises this limit on some orders of magnitude higher then the resolution of thermal image. Corresponding calculation will be done and will be verified experimentally. From the other hand regimes of laser irradiation (power density, time of irradiation etc) as well as regimes of selective etching (type of etchant and its concentration), material of thin film and its thickness have also big influence on the final results. Experimental and practical results for fabrication of many specific components and devices as dif-ferent diffraction lenses, diffraction attenuators, synthesized holograms will be demonstrated.

Relation Between Morphology, Etch Rate, Surface Wetting, and Electrochemical Characteristics for Micromachined Silicon Subject to Galvanic Corrosion

Immersion of silicon in HF-based solutions is utilized in microsystems fabrication to render freestanding mechanical structures. Such etching, however, creates a galvanic couple between silicon and a metallic layer (e.g., gold), resulting in corrosion damage. Morphology, resistive probe, surface wetting, and electrochemical characterization (vs ) of single- and polycrystalline silicon subjected to galvanic corrosion in three HF-based solutions (undiluted 48% HF, , and UDHF:Triton X-100) are used here to formally substantiate the results of a previous mechanical (microtensile) study. Porosity estimated from the morphology of corroded samples allows the corrosion current density to be determined from etch-rate measurements, according to Faraday’s law. Resistive probe structures are used to simulate the microtensile specimens, thereby characterizing corrosion current as a function of time, etchant type, illumination, and the amount of metal utilized. The measured current density of micromachined silicon is compared against (100) wafer specimens using polarization characterization, identifying the porous Si formation regime. Using sessile drop measurements, the three etchants are further distinguished based on their surface-wetting characteristics. The chronopotentiometry, resistive probe, and microtensile characterizations all identify the behavior regimes of rapid initiation, subsequent steady-state corrosion, and the final catastrophic failure of the microtensile specimens.

Selective wet-etching and characterization of chalcogenide thin films in inorganic alkaline solutions

This paper deals with sensitivity of chalcogenide based photoresists in inorganic alkaline solutions. The thin films of As33S67, As33S50Se17, As33S33.5Se33.5, As33S17Se50, and As33Se67 were studied. The selective wet-etching was carried out using NaOH, Na2S and (NH4)2S alkaline solutions. The different sensitivity according to sample composition and used etching solution were found. Chalcogenide films as a potential photoresists could be classified either as ‘high-contrast’ or ‘low-contrast’ depending on the sample compositions, type of etchant and its concentration or on incident light energy.

⟨1 0 0⟩ bar corner compensation for CMOS compatible anisotropic TMAH etching

For a long time wet bulk-micromachining has been an easy and cost-effective method for fabricating silicon micro-sensors. Anisotropic wet etching is the key processing step for the fabrication of microstructures. Among different silicon etchants, TMAH based etchants are becoming popular because of their low toxicity and CMOS compatibility. The etch rate of wet anisotropic etching of silicon depends on the crystal plane orientation, type of etchant and their concentrations. In anisotropic etching, convex corners are attacked; therefore, a proper compensating structure design is often required when fabricating microstructures with sharp corners (convex corners). In the present work, two ⟨1 0 0⟩ bar compensation structures have been used for convex corner compensation with 25% wt TMAH–water solution at 90 ± 1 °C temperature. Generalized empirical formulae are also presented for these compensation structures for TMAH–water solution. Both the ⟨1 0 0⟩ bar structures provide perfect convex corners but the ⟨1 0 0⟩ wide bar (structure 2) is more space efficient than the ⟨1 0 0⟩ thin bar (structure 1) and it requires nearly 30% less groove width.

Selective wet-etching of undoped and silver photodoped amorphous thin films of chalcogenide glasses in inorganic alkaline solutions

The unexposed/exposed, Ag-rich (exposed)/Ag-poor (unexposed) and amorphous (unexposed)/crystallized (exposed) parts of vacuum evaporated amorphous chalcogenide films of composition As33S67, As33S50Se17, As33S33.5Se33.5, As33S17Se50, As33Se67, Agx(As33S67)100−x and Agx(As33S33.5Se33.5)100−x were selectively etched in water solutions of inorganic alkaline substances (NaOH, Na2S, (NH4)2S, Na2CO3 and NaCN). Different etching rates for exposed and unexposed parts were found depending upon the sample composition, type of etchant and its concentration. A resolution coefficient, γ, was confirmed by selectively etched films after their exposure through a gray-scale photomask with microlenses array motives.

Anisotropic wet etching on birefringent calcite crystal

In this paper, a mechanism for wet etching on birefringent calcite crystal is discussed. By altering the etchant type, its concentration and the stirring speed, the etching mechanism can be confined within the surface reaction regime, resulting in anisotropic etching. Acetic acid can be used to form V shapes defined by the {1011} planes with an intersecting angle of 51 degree. V-groove and blazed grating, with a grating period as small as 2 μm, were successfully fabricated. Such gratings can be used as transmission and reflection devices in the visible and infrared ranges. In addition, a transmission polarization dependent device can also be made by covering the calcite with index matching material.

The effect of selective chemical etching on the directivity pattern for radiation of a semiconductor laser

The effect of the selective wet chemical etching of the emitting surface on the directivity pattern of radiation in the plane normal to the p-n junction is studied for InGaP/GaAs lasers with InGaAs quantum wells. It is found by atomic-force microscopy that the cylindrical lens (converging or diverging, depending on the type of etchant) is self-formed on the emitting surface due to the different etching rate of wide-gap layers (InGaP) and active layers (GaAs, InGaAs) of the lasers. By adjusting the corresponding etching time, the aperture angle of the laser radiation pattern in the plane normal to the p-n junction can be changed in the range of 57°–82° at the initial aperture angle at the half maximum level of 6°.

Etched Single-Ion-Track Templates for Single Nanowire Synthesis

Polycarbonate membranes with one pore only are created by the track-etching technique. The shape and size of the pore are determined by the type of etchant as well as by the temperature and etching time. The dynamics of single-pore formation during etching is investigated to determine the breakthrough time and the track-etching rate. The pore is characterized by electrical conductivity measurements and scanning electron microscopy. This kind of template is employed for the electrochemical deposition of a single bismuth wire that is left in the polymer for further measurements of its electrical properties.

Reactivity at Line Defects in Antimony in Etchants with Dextro‐ and Levo Tartaric Acid

AbstractThe (111) cleavage faces of antimony single crystals were etched in aqueous mixtures of fuming nitric acid plus dextro tartaric acid and fuming nitric acid plus levo tartaric acid. Triangular, crystallographically oriented etch pits were observed at sites of dislocations. The activation energies for lateral motion of ledges and the frequency factors were calculated for both types of etchants which were found to be higher in levo tartaric acid containing etchants than in dextro tartaric acid containing etchants. The results are explained in terms of antimony complexes and the difference in the shape of dextro tartaric acid and levo tartaric acid molecular structures.

The Electrochemical Nature of GaAs in Acids: A Comparison with InP

The chemical composition of surface oxides grown on was investigated using x‐ray diffraction techniques. Native oxides were prepared by exposing the to and etchants at concentrations ranging from pH 5 to the maximum acidities available. A mixture of crystalline stoichiometric phases were formed. The chemical oxides appear to be more complex than indicated by previous studies by x‐ray photoelectron spectroscopy, but were independent of the type of etchant or its acidity. Only constituent oxides, rather than mixed oxides, were found on the oxidized surface. The thermodynamics may play a key role in the reaction pathway. In the etch, GaI and GaI‐Ga III chloro compounds are not formed, and the dissolution of is severely inhibited even in the most acidic solutions under illumination. This complete absence of nucleophilic attack of the Ga‒As bond by a Cl− ion is reasonably well explained by the fact that the intermediate, , is not thermodynamically stable.