Etching Temperature Research Articles

An Evaluation of Corrosion Inhibitors for Use in Acid Decapsulation of Samples with Silver Bond Wires

Abstract Silver bond wires can be protected from damage during acid decapsulation by injecting a corrosion inhibitor into the acid stream. Recent experiments show that the injection of an iodic acid solution is effective over a wide range of process parameters, including etch time, etch temperature, and the amount of inhibitor injected. The results presented in the article are based on the use of a 0.3 M iodic acid solution and the decapsulation of parts containing silver alloy wire. However, similar results have been achieved on test samples with pure silver wire using a higher concentration inhibitor solution. Both solutions have very long shelf life and are relatively safe to handle.

Fabrication of through-silicon via arrays by photo-assisted electrochemical etching and supercritical electroplating

This paper aims to fabricate high aspect ratio through silicon via (TSV) by photo-assisted electrochemical etching (PAECE) and supercritical CO2 copper electroplating. A blind-holed silicon array was first fabricated by PAECE. By studying the etching parameters, including hydrofluoric acid concentration, etchant temperature, stirring speed, tetrabutylammonium perchlorate (TBAP) content, and Ohmic contact thickness, an array of pores with a 1∶45 aspect ratio (height=250 μm and diameter=5.5 μm) was obtained successfully. Moreover, TBAP and Kodak Photo-Flo (PF) solution were added into the etchant to acquire smooth sidewalls for the first time. TBAP was added for the first time to serve as an antistatic agent in deionized water-based etchant to prevent side-branch etching, and PF was used to degasify hydrogen bubbles in the etchant. The effect of gold thickness over Ohmic contact was investigated. Randomized etching was observed with an Au thickness of 200 Å, but it can be improved by increasing the etching voltage. The silicon mold of through-holes was filled with metal using supercritical CO2 copper electroplating, which features high diffusivity, permeability, and density. The TSV structure (aspect ratio=1∶35) was obtained at a supercritical pressure of 2000 psi, temperature of 50°C, and current density of 30 mA/cm2 in 2.5 h.

Surface roughness and morphology evolution of optical glass with micro-cracks during chemical etching.

Chemical etching is usually utilized to measure, reduce, and remove the subsurface micro-cracks in optical components, which makes it significant to study the surface evolution of optical components during the etching process. Etching experiments were carried out for glass with artificial cracks and micro-cracks under different etching conditions. The etching rate was obtained, which is linear with the hydrofluoric acid (HF) concentration and greatly affected by etching temperature. By measuring the surface roughness (SR) and morphology of glasses after etching, it is found that the crack width always increases with etching time, while the crack depth remains unchanged after the crack is completely exposed. Meanwhile, the SR increases sharply at first, then increases slowly, and finally decreases with the increase of etching time. Considering the influence of HF concentration, etching temperature, and the diffusion coefficient on the etching rate, simulation models were established for etching trailing indent cracks (TICs) to further analyze the evolution of SR and morphology. The simulation results were compared with the experimental ones, also indicating that the maximum SR (Ra) increases greatly with the crack's aspect ratio and the model for analyzing the crack's morphology evolution is more reasonable.

Fabrication of ZnO nanowire-silicon pyramid hierarchical structure, and its self-cleaning

The transmittance diminishment of solar cells, caused by dust accumulation is higher than 52.54% every year (2006 Energ. Convers. Manage. 47 3192), which greatly reduces their overall efficiencies of power conversion. Any other strategy for improving the photovoltaic device cannot compensate for this loss caused by the dust. However, this critical issue has not received much attention. In this work, a kind of self-cleaning coating consisting of ZnO nanowire-silicon pyramid hierarchical structures is proposed to overcome the dust accumulation on the photovoltaic device. The principle of designing this self-cleaning is based on the Cassie-Baxter theory. Both the micron size effect for superhydrophobicity and the performance of anti-reflection of light of the substrate should be retained, which are the requirements of application of solar cell. The pyramid-like silicon (named silicon pyramid, hereafter) is fabricated by simple chemical etching. The effects of isopropanol, KOH, etching time, and etching temperature on the morphology of the silicon pyramid are investigated by using systematic statistical design and analysis method, to obtain the best distribution and size of the silicon pyramid. In the systematic statistical design and analysis method, the pick-the-winner rule is adopted. Eventually, we find that the optimized conditions for etching silicon pyramid (according the requirements of self-clean) are as follows: etching time is 60 min, etching temperature is 95℃, and mixture is 80 mL DI water, 2.9598 g KOH and 20 mL isopropanol. Moreover, ZnO nanowire-silicon pyramid hierarchical structures for the application of photovoltaic device are successfully hydrothermally grown on the substrate of silicon pyramid for the first time. The obtained self-cleaning coating consists of ZnO nanowire (with a diameter of 136 nm) and silicon pyramid (with a size of 8-11 m). The surface of this coating possesses superhydrophobic properties, i.e., a water contact angle of 154 and a contact angle hysteresis of less than 10, after being modified by heptadecafluorodecyltrimethoxysilane. Also, our obtained ZnO nanowire-silicon pyramid hierarchical structures have quite a good performance of anti-reflection, which appear gray in the normal environment. And the mechanism for it is postulated. Importantly, some new phenomena, such as high temperature improving the growth of silicon pyramid, are also revealed. Besides, the physical mechanism for high temperature improving the growth of silicon pyramid and anisotropic etching of silicon substrate is discussed. It is indicated that the anisotropic behavior is attributed to small difference in energy level (being a function of the crystal orientation) between the back-bond surface states. The method we proposed to achieve self-cleaning coating is versatile, reliable and low-cost, which is also compatible with contemporary micro-and nano-fabrication processes.

GRA and ANN Integrated Approach for Photochemical Machining of Al/SiC Composite

Metal Matrix Composites (MMCs) have evoked a keen interest in recent times for potential applications in aerospace and automotive industries owing to their superior strength to weight ratio and high temperature resistance. Stir casting technology along with additives is used to achieve uniform distribution of reinforcement within the matrix that affects the properties of composite material. The attempt has been made to develop aluminium based silicon carbide particulate AMCs and optimize the process parameters in photochemical machining of composites. In the present study, the effect of various control parameters such as time of etching, temperature of etchant and concentration of etchant on Material Removal Rate, Undercut and Etch factor in PCM of Al/Sic has been investigated by using integrated DoE and Gray relational analysis. Mathematical models relating to the performance of machining parameters have been formulated. The optimal machining parameter was observed at etching temperature of 60°C, etching concentration of 700 gm/lit. and etching time of 12 minutes. The result obtained after the confirmatory test prove that improvement in the machining quality will take place if the setting of the machining parameters done at optimum level.

Investigation on Surface Roughness of Inconel 718 in Photochemical Machining

The present work is focused on estimating the optimal machining parameters required for photochemical machining (PCM) of an Inconel 718 and effects of these parameters on surface topology. An experimental analysis was carried out to identify optimal values of parameters using ferric chloride (FeCl3) as an etchant. The parameters considered in this analysis are concentration of etchant, etching time, and etchant temperature. The experimental analysis shows that etching performance as well as surface topology improved by appropriate selection of etching process parameters. Temperature of the etchant found to be dominant parameter in the PCM of Inconel 718 for surface roughness. At optimal etching conditions, surface roughness was found to be 0.201 μm.

On-axis Si-face 4H-SiC epitaxial growth with enhanced polytype stability by controlling micro-steps during the H2 etching process

In situ H2 etching and homoepitaxial growth of 4H-SiC were performed on on-axis Si-face substrates using low-pressure chemical vapor deposition. We investigated the effect of various etching temperatures and durations on the surface of the on-axis substrates and used optimized etching characteristics to enhance the polytype stability of the epitaxial layer. It was found that the micro-steps at the etched surface of the on-axis substrates play a vital role in enhancing the stability of the 4H-SiC polytype. Homoepitaxial 4H-SiC with up to 99% stability was successfully grown with spread-out micro-steps without step-bunching during the etching process.

Effects of etching conditions on surface morphology of periodic inverted trapezoidal patterned Si(100) substrate

In this paper, the anisotropic etching process of Si(100) wafers in tetramethyl ammonium hydroxide (TMAH) solution with isopropyl alcohol (IPA) is investigated in detail. An inverted trapezoidal pattern is developed. A series of experiments are performed by changing TMAH concentration, IPA concentration, etching temperature and etching time. The structure of inverted trapezoidal patterns and roughness of the bottom surface are characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results show that with TMAH concentration increases, the roughness of bottom surface will decrease. The addition of IPA into TMAH solution improves the morphology of the bottom surface significantly. Low temperature is beneficial to get a smooth bottom surface. Furthermore, etching time can change the bottom surface roughness. A model is proposed to explain the etching processes. The hillock area ratio of the bottom surface has the same tendency as the etching area ratio. Finally, smooth silicon inverted trapezoidal patterns are obtained for epitaxial growth of GaN-based light emitting diode (LED) devices.

AFM and SEM Study on Crystallographic and Topographical Evolutions of Wet-Etched Patterned Sapphire Substrate (PSS): Part III. Cone-Shaped PSS Etched in H2SO4 and H3PO4 Mixture at Various Temperatures

The effect of etching temperature (473–543 K) on the crystallographic and topographical evolutions as well as the etching rate of crystallographic planes of cone-shaped patterned sapphire substrate (PSS) etched in both H2SO4-based (H2SO4:H3PO4 = 5:1 at volume ratio) and H3PO4 etchants was systematically studied. For H2SO4-based etchant, higher temperature favors larger etching rate ratio of slant planes (S1 {1 0 5}, S3 {4 1 38}, S4 {1 0 12}, and S5 { 1 0 37} planes) to c-plane, thus leading to smaller filling factor (FF) of patterns; the Arrhenius activation energy (Ea) of etching reactions for various crystallographic planes follows the order: Ea (c) < Ea (S1) < Ea (S3) < Ea (S4). For H3PO4, higher temperature favors smaller etching rate ratio of slant planes (S1 {1 0 5} and S6 {1 0 8} planes) to c-plane and larger FF of patterns; the Ea follows the order: Ea (S1) < Ea (S6) < Ea (c). This work will contribute to elucidating the etching mechanism and fabricating optimized PSS for enhanced performance of light emitting diodes.

Basis for the alkaline removal process design of the alumina-based ceramic core

The basic physico-chemical behaviors and laws of etching an alumina-based ceramic core out of investment castings still puzzle the process designer. To investigate the basis, ceramic removal experiments were performed at normal pressure by varying several main factors. The de-coring rate increased as the etching temperature increased. A higher alkali concentration was beneficial to the removal efficiency but had an upper limit because of the metal alkaline corrosion. The de-coring rate underwent a convex-curve variation as the etching time increased since the deposition of a validated insoluble product gradually hinders the etching reaction. The solute additive KCl and solvent additive ethanol have the positive effects of improving the reactivity of the base solution and increasing the permeability of the etching liquid, respectively. The de-coring rate was up to 10.46 wt %·h−1 in a steady process with etching in a 70 wt % KOH solution supplemented with 10 wt % KCl and ethanol.

Synthesis and characterization of aluminum carbide-derived carbon with residual aluminum-based nanoparticles

An in-depth study on the etching process for producing carbide-derived carbons from Al4C3 has been performed. These materials were investigated at a range of etching temperatures from 300 to 900 °C and a range of times from 15 min to 6 h. By altering the etching time and temperature, the surface area, residual aluminum content, and pore size distribution can be tuned. A maximum surface area of 1126 m2 g−1 was observed for materials etched at 500 °C for 1 h. The pore size has shown to be tunable from ≤0.7 to 8 nm. Interestingly, aluminum-based nanoparticles were observed via TEM and SEM for partially etched samples, with evidence of tunable metal species on the surface of the Al4C3-CDC samples at different etching temperatures between 300 and 700 °C. Characterization of the aluminum species present over this temperature range took place using solid-state 27Al NMR. The formation of crystalline α-Al2O3 was observed at etching temperatures of 700 °C. The results of this work provide detailed synthesis strategies for controlling not only the porosity and surface area of a carbide-derived carbon, but also the extent and type of residual metal nanoparticles embedded in the final structure.

Synthesis of two-dimensional Ti3C2Tx MXene using HCl+LiF etchant: Enhanced exfoliation and delamination

Herein, enhanced exfoliation and large-scale delamination of two-dimensional (2D) Ti3C2Tx MXene using etchant of HCl + LiF, instead of HF, in which both etching and intercalation were achieved in exfoliation process, were thoroughly investigated with the focus on the effects of two critical factors, reaction temperature and washing solution. Increasing etching temperature promotes the exfoliation process, i.e., the transformation from Ti3AlC2 to multilayer Ti3C2Tx MXene, whereas simultaneously results in an aggravated surface oxidation of MXene layers formed after the extraction of Al. As a result, delamination ratio increases firstly and then decreases, and the samples etched at 35 °C show the highest delamination ratio. Compared with the distilled water, washing the exfoliation products using ethanol significantly improves the delamination ratio of Ti3C2Tx MXene by co-intercalation of larger alcohol molecule and more impurity ions and a large scale delamination of Ti3C2Tx MXene with a delamination ratio as high as 29.2% was obtained by simple sonication for 1 h, without additional intercalation step required, after washing using ethanol. The possible exfoliation reactions by HCl + LiF solution were proposed. Using the as-fabricated stable suspensions of delaminated Ti3C2Tx flakes, flexible, free-standing Ti3C2Tx papers with tailored thickness, hydrophilic surface and excellent conductivity, typically 2 × 105 S/m at 5 μm in thickness, were prepared. As anode for lithium ion batteries, the delaminated Ti3C2Tx MXene obtained reversible capacities of 226.3 mAh g−1, 137.9 mAh g−1,102.0 mAh g−1 and 47.9 mAh g−1 respectively at the current density of 100, 300, 1000 and 3000 mA g−1, which are superior to those of the Ti3C2 MXene prepared by conventional HF process.

Effect of process parameters and optimization for photochemical machining of brass and german silver

ABSTRACTThis article focuses on parametric optimization for photochemical machining (PCM) of brass and german silver. The aim of the study is to analyze the effect of control parameters on response measures, that is, surface roughness, material removal rate, and edge deviation and optimization of parameters considering different weight percentage for each performance measure. The control parameters have been selected as etchant concentration, etching temperature, and etching time. Using full factorial method of design of experiments, PCM has been carried out using ferric chloride as etchant. Surface roughness and edge deviation should be less, while material removal rate is desired high. For satisfying this multi-objective condition, overall evaluation criteria (OEC) have been formulated by assigning different and equal weight percentage to response measures. The optimized condition for particular OEC is obtained, and analysis of variance (ANOVA) has been performed for observing effect of control parameters on response measures. Surface topography study has been performed using scanning electron microscopy, and material composition analysis has been carried out using energy dispersive spectroscopy. The surface roughness is observed lower for brass, while the edge deviation is found lesser for german silver. The material removal rate is observed higher for brass compared to german silver.

Low temperature dry etching of chromium towards control at sub-5 nm dimensions

Patterned chromium and its compounds are crucial materials for nanoscale patterning and chromium based devices. Here we investigate how temperature can be used to control chromium etching using chlorine/oxygen gas mixtures. Oxygen/chlorine ratios between 0% and 100% and temperatures between −100 °C and +40 °C are studied. Spectroscopic ellipsometry is used to precisely measure rates, chlorination, and the thickness dependence of n and k. Working in the extremes of oxygen content (very high or very low) and lower temperatures, we find rates can be controlled to nanometers per minute. Activation energies are measured and show that etch mechanisms are both temperature and oxygen level dependent. Furthermore, we find that etching temperature can manipulate the surface chemistry. One surprising consequence is that at low oxygen levels, Etching rates increase with decreasing temperature. Preliminary feature-profile studies show the extremes of temperature and oxygen provide advantages over commonly used room temperature processing conditions. One example is with higher ion energies at −100 °C, where etching products deposit.

Effects of the surface morphologies of ZnO nanotube arrays on the performance of amperometric glucose sensors

Amperometric glucose sensors have been fabricated with glucose oxidase (GOx) immobilized on ZnO nanotubes (ZnONTs) by physical adsorption. The ZnONTs were formed through selective dissolution of ZnO nanorods (ZnONRs) which were hydrothermally synthesized on Au cylindrical spiral (AuCS) electrodes. With the etching temperature regulated, the surface morphologies of the ZnONT arrays were tailored and their effects on the performance of the corresponding glucose sensors were investigated. It is found that at 65°C the as-prepared ZnONT arrays show a Gaussian rough surface with larger surface area and better hydrophilicity, and have an effective solid–liquid interface with GOx solution, which further results in desirable GOx immobilization. Therefore favorable performance of the ZnONT-based glucose sensor was obtained, such as the sensitivity 2.63 μA/(mMcm2), linear range 0–6.5mM, low detection limit 8μM (S/N=3) and Michaelis-Menten constant 5.24mM, which are superior to that of the ZnONR-based one. Moreover, the ZnONT-based glucose sensor exhibits good long-term stability, and excellent anti-interference ability to uric acid and ascorbic acid. The results can also be used for the performance optimization and the process standardization of other ZnONT-based amperometric biosensors.

Etch Mechanism and Temperature Regimes of an Atmospheric Pressure Chlorine-Based Plasma Jet Process

Etch Mechanism and Temperature Regimes of an Atmospheric Pressure Chlorine-Based Plasma Jet Process

SIMULATION STUDY OF CONVEX CORNER UNDERCUTTING IN KOH AND TMAH FOR A MEMS PIEZORESISTIVE ACCELEROMETER

Undercutting is a common problem in wet anisotropic etching. This problem in turn, influences the performance and sensitivity of MEMS devices. This paper investigates the use of corner compensation to prevent convex corner undercutting in a MEMS piezoresistive accelerometer. The Intellisuite CAD simulation software was used for designing the mask with corner compensation and for analysing wet anisotropic etching profiles in potassium hydroxide (KOH) and tetra-methyl-ammonium-hydroxide (TMAH) solutions at different concentrations and temperatures. Perfect 90 degrees corners on the proof mass was successfully etched using a corner compensation design at etching temperature of 63 °C for KOH and 67.7 °C for TMAH with 25 wt% and 10.3 wt% concentration levels, respectively. Etching in TMAH required lower concentration level, thus making the etching process safer. However, TMAH required longer time to etch perfect convex corners compared to KOH. Nevertheless, both KOH and TMAH etchants have been successfully used to etch perfect convex corners by using the designed corner compensation mask.

&lt;i&gt;In Situ&lt;/i&gt; Cleaning Process of Silicon Carbide Epitaxial Reactor for Removing Film-Type Deposition Formed on Susceptor

The in situ cleaning process of a silicon carbide epitaxial reactor was developed using chlorine trifluoride gas for removing the film-type silicon carbide deposition formed on a susceptor. By adjusting the etching temperature to less than 330 °C, the formed silicon carbide films could be removed without significant damage to the susceptor.

Temperature-Dependent Nanofabrication on Silicon by Friction-Induced Selective Etching.

Friction-induced selective etching provides a convenient and practical way for fabricating protrusive nanostructures. A further understanding of this method is very important for establishing a controllable nanofabrication process. In this study, the effect of etching temperature on the formation of protrusive hillocks and surface properties of the etched silicon surface was investigated. It is found that the height of the hillock produced by selective etching increases with the etching temperature before the collapse of the hillock. The temperature-dependent selective etching rate can be fitted well by the Arrhenius equation. The etching at higher temperature can cause rougher silicon surface with a little lower elastic modulus and hardness. The contact angle of the etched silicon surface decreases with the etching temperature. It is also noted that no obvious contamination can be detected on silicon surface after etching at different temperatures. As a result, the optimized condition for the selective etching was addressed. The present study provides a new insight into the control and application of friction-induced selective nanofabrication.

Preparation of Large-Area Porous Silicon through Cu-Assisted Chemical Etching

Porous silicon (PS) was prepared with catalyst of Cu nanoparticles in HF/H2O2 solutions. The effects of the key fabrication parameters (amount of copper, etching temperature and concentration of H2O2) on the nanostructure of PS were systematically investigated and discussed. The experimental results indicated that the porosity of PS increased with the amount of copper, the reaction temperature and the concentration of H2O2, respectively. Copper can be used as catalyst to assist in etching silicon and the evolution process of copper nanoparticles was explored showing that the mass of copper experienced a drastic reduction in the first 60 seconds. A mechanism is proposed to explain the formation of PS by Cu-assisted chemical etching.