Aluminum Etching Research Articles

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Aluminum was electrochemically etched in acid solution and the surface area was magnified by the formation of etch pits. Etched aluminum was covered with a compact and dense dielectric oxide film by anodization and applied to the aluminum electrolytic capacitor electrode. Capacitance of aluminum electrolytic capacitor is closely related with surface area, which depends on size and number of etch pits. Size of etch pits need to be controlled because inside of the pits can be buried by the formation of dielectric oxide film. In this work, the effect of ultrasound pretreatment on the aluminum etch pit formation and capacitance were investigated. Additionally, the relationship between the second etching effect on pit size and capacitance was studied.

Synthesis of Zeolite A from By-Product of Aluminum Etching Process: Effects of Reaction Temperature and Reaction Time on Pore Volume

Problem statement: Increasing of the carbon dioxide (CO2) concentration in the atmosphere creates a global warming. Zeolite is used as CO2 absorbent. Approach: By-products from aluminum etching process, which carry a large amount of Al2O3 content, are useable as raw materials for synthesis zeolites type A using hydrogel process. A pore volume of zeolites is the key to achieve high CO2 absorption capacity. In this study, two-factor factorial experiments with 3 replicates and α = 0.05 have been conducted to examine the influence of reaction temperature and reaction time on the pore volume and to determine the process conditions for containing the highest pore volume. Three levels of the reaction temperature of 75, 85 and 95°C and three levels of the reaction time of 1, 2 and 3 h (s), while the stirring speed is controlled at 300 rpm, are selected for the experiment. The mole ratios of the starting reactants are fixed at 2 of SiO2/Al2O3, 2 of Na2O/ Al2O3 and 85 of H2O/Na2O. Analysis of surface area is performed by the BJH method and the DR method for analysis of gas adsorption- desorption using nitrogen. Results: The results found that there was significant interaction between the reaction temperature and the reaction time and at 95°C of 3 hours gave the highest pore volume, resulting in 0.0205cc g −1 of the BJH method and 0.0065 cc g −1 in the DR method. Besides, the CO2 absorption test is also performed with the zeolite synthesized at 95°C. Conclusion: Zeolite syntheses of by product from alkaline etching of the aluminum industry have a major analysis agree well with those of reference zeolite A. Adsorption test with CO2, yield the best result with ZA31, with the capacity of 0.1023 ccg -1 .

Crown Defect Reduction and Cp Yield Improvement for High Voltage Power Management IC Product

In advanced BEOL process, metal defect reduction plays an important role for Cp yield improvement. "Crown defect" is one of the killer defects. It develops in Litho process, forms after Aluminum etching, and finally turns out to be ring-type Al2O3 residue. Aluminum grain size is strongly related with crown defect performance. Especially for thick Aluminum film (>3μm), which is widely applied on high voltage power management IC product, it is a big challenge to control grain size and keep a relatively uniform film surface. In this paper, a study of the relationship between Aluminum grain size and crown defect is presented. Also, a novel approach to control the grain size is shown to reduce the crown defect for Cp yield improvement.

Preparation and Corrosion Resistance of TiCN/Al Composite Foil for Capacitor

A new TiCN/Al composite foil for capacitor negative applications was prepared by multi-arc ion plating method.The effects of cooling process and flow ratio of C2H2 to N2 for deposition on specific capacitance were investigated.The polarization curves were measured for TiCN/Al composite foil and traditional etching aluminum foil and their corrosion resistance were compared and discussed.Specific capacitance of TiCN/Al composite foil obtained is as high as 1600μF/cm2 which is over two times higher than that of the aluminum foil prepared using the traditional etching process.The TiCN/Al composite foil shows a wide range of stable passivation zone in the capacitor electrolyte solution and its corrosion resistance is significantly higher than that of the aluminum foil fabricated by the traditional etching process.

Hydrogen Permeability and Membrane Durability of Novel Pd/.GAMMA.-Alumina Graded Membrane When a Sweep Gas is Used

In this study, Pd/γ-alumina graded membranes were fabricated by an electroless plating method on nanoporous γ-alumina formed by anodic oxidation of an etched aluminum support, and the H2 permeability of the membranes was determined. The Pd/γ-alumina graded membrane on the etched aluminum support was prepared by carrying out electroless plating for 30 min, and for 60 min. In the first case of electroless plating for 30 min, Pd/γ-alumina graded membrane with a thickness of 2.5 μm, H2 flux of 0.28 mol m−2 s−1, and H2/N2 permselectivity of 817 were obtained. In the second case of electroless plating for 60 min, Pd/γ-alumina graded membrane with a thickenss of 4.5 μm, H2 flux of 0.17 mol m−2 s−1, H2/N2 permselectivity of 5259 were obtained. In durability tests, it was observed that the H2 flux increased with time in the initial stage and then become approximately constant after 70 h. The graded membrane exhibited high durability. The membrane formed by 60 min of electroless plating was heated at 773 K for 12 h in a furnace (preheated Pd/γ-alumina graded membrane). The H2 flux of the preheated graded membrane remined approximately constant during the durability test. This result implies that the Pd/γ-alumina graded membrane for the optimum H2 permeation was not obtained by heating because the Pd crystals formed by electroless plating, and recrystallized to form larger grains; this happened because of heating, hybridization of γ-alumina and Pd, and influence of annealing. Finally, we successfully fabricated novel Pd/γ-alumina graded membranes that exhibited high H2/N2 permselectivity, H2 permeability, and durability.

Gas assisted focused electron beam induced etching of alumina

This study investigates focused electron beam induced etching for the removal of alumina particles on patterned extreme ultra violet (EUV) mask using nitrosyl chloride (NOCl) as assist gas. As potential contaminant, particles of aluminum oxide (alumina, Al2O3) have been successfully removed, leaving the underlying layers undamaged. Particles were applied onto an EUV mask, consisting of a multilayer Bragg mirror capped with a thin ruthenium layer and a structured tantalum nitride (TaN∕TaON) absorber/antireflective film. Alumina particles were selectively etched using the chlorine-based gas, NOCl. Neither the Ru nor the absorber was significantly etched during the process in spite of a square area scanned by the focused electron beam being larger than the particle. The process resolution is discussed based on Monte Carlo electron scattering simulations. Thermodynamic driving forces for the electron-induced reactions and its selectivity are discussed and a chemical rationale is proposed.

In-situ observation of nucleation on a rough chilling surface in NH4Cl-H2O solution

The nucleation behaviors of NH4Cl crystal on a rough chilling surface immerged in NH4Cl-H2O solution were investigated. A phenomenon was found that the nuclei are formed periodically on certain spots of the undercooled surface. The relationship between the surface roughness and the nucleation site selection was investigated on abrasive paper polished aluminum substrate, and it is discovered that the number of nucleation sites decreases significantly with the decreasing roughness of the polished substrate. Further nucleation experiments were carried out on chemical etched aluminum substrate with regular micro-patterns, the result shows that the selection of nucleation sites was more sensitive to the micro-patterns rather than the surface roughness of the interface, and the interfaces with sharp nanometer structures were feasible for the nucleation on the interface.

Surface studies of 2,4-pentanedione on γ-Al 2O 3/NiAl (1 0 0) and NiAl (1 0 0)

The chemical compound 2,4-pentanedione (Hacac) has been shown to etch the oxidized metal surfaces metals such as copper and nickel, but not their unoxidized surfaces. Here it is shown that on the γ-Al 2O 3/NiAl (1 0 0) surface (oxidized NiAl (1 0 0)) etching of aluminum occurs at 170 K and 750 K. Reflection–absorption infrared spectroscopy (RAIRS) is used to show that Hacac binds to both the clean, metallic and oxidized surfaces, but decomposition and combustion products dominate on the metallic surface and no etching occurs. The binding process that involves a deprotonation reaction of the enol species was identified by redshift in the carbonyl peaks and the appearance of an Al–H peak observed in the IR spectrum. The implication of these results is that there is both an unusual low temperature and high temperature etching of the alumina by bound acac.

Pattern transfer on a vertical cavity sidewall using SU8

In this paper, a process to realize metal lines on the sidewall of high aspect ratio cavities is developed. As an alternative to conventional photoresist, SU8 is used to define patterns on vertical sidewalls of deep cavities while maintaining compatibility with conventional IC processes. When transferring a pattern onto a 3D structure, especially the coating process, cavity filling and step coverage become important issues and require specific attention. A highly uniform SU8 coating is obtained and 20 µm wide aluminium lines across 60 µm deep cavities are realized. Problems related to overexposure and to aluminium etching are presented as well. The resistance of the aluminium structures on top, bottom and sidewall of the cavities is measured and discussed.

Single-bead-based consecutive biochemical assays using a dielectrophoretic microfluidic platform

In this paper, we describe a method for performing single-bead-based, consecutive biochemical assays on a dielectrophoretic microfluidic chip using the interaction of FITC-labeled streptavidin with biotin-coated 2-μm polystyrene (PS) beads as a model system. A microfluidic device with four sets of electrodes on a glass slide was used to trap a single bead at the center of each set of electrodes through negative dielectrophoresis. Each set of electrodes was composed of four electrodes arranged in a cross-like manner. The electrodes were prepared using a simple process consisting of UV lithography and aluminum etching. A laser-induced fluorescence system detected the fluorescence emission from the FITC-labeled streptavidin conjugated with the biotin-coated PS beads. We investigated the effects of (i) the magnification/numerical aperture of the objective used for collecting fluorescence signals and (ii) the cut-off frequency of the low-pass digital filter, which filtered out high-frequency noise, on the signal-to-noise ratio. The average measured fluorescence maximum, determined from 10 consecutive fluorescence signals, increased with increasing concentrations of streptavidin (up to 0.3μg/mL); it leveled off when the concentration of streptavidin was greater than 0.3μg/mL. The limit of detection (signal-to-noise ratio=3.0) was 8.3ng/mL.

Applicability of Metallic Nanoparticle Inks in RFID Applications

Radio frequency identification (RFID) antennas for HF and UHF frequencies are ink-jet printed using commercially available silver nanoparticle ink. Quality factors of 5.3 and 9.4 are obtained for coil antennas targeted for 13.56 MHz when the printing and sintering process is repeated two and three times, respectively. The measured maximum effective aperture of the printed UHF antenna is only some decibels lower than that of an equivalent etched copper antenna and the maximum reading distance with 0.5 W (ERP) transmitted power is 3 m for continuous reading. These results suggest that obtaining a low enough series resistance for printed coils is challenging while printed RFID antennas for UHF do not set as strict requirements on conductivity. With a perfectly optimized structure, a UHF tag antenna printed in just one layer of ink can be practically equal in performance with the traditional etched copper and aluminum tags.

Optical Transmission Spectra of Anodic Aluminum Oxide Membranes with a Dual Layer-by-Layer Structure

By adjusting the anodization voltage periodically in the process of electrochemical oxidation of aluminum and subsequent chemical etching, anodic aluminum oxide membranes with a dual periodic layer-by-layer structure are prepared. Optical transmission spectra analyses prove that the dip position is dependent on the thickness of the layer and can be easily adjusted by the anodization voltage according to the Bragg–Snell formula. This result implies that the position and width of the stop band and the pass band in the visible and near infrared wavelength region can be designed and prepared arbitrarily. It is expected that these kinds of anodic aluminum oxide membranes may find applications in the fabrication of various optical devices.

Preparation of Porous Anodic Alumina with Periodically Perforated Pores

Anodization of aluminum is an excellent nonlithographic alternative to conventional fabrication approaches for low-cost and large-scale synthesis of a variety of nanostructured materials. In this work, the preparation of anodic alumina oxide (AAO) with unique three-dimensional (3D) porous structures that consist of periodically perforated nanopores is reported. The fabrication method combines electrochemical anodization of aluminum and chemical etching. The key feature of this process is cyclic anodization where an oscillatory current signal was applied to create AAO with periodically shaped pore structures. Spatially specific dissolution of the pore walls was directed by modulated pore structures during chemical etching to generate hexagonally ordered arrays of holes with periodic distribution across the pore length.

Characterization of Post Etch Residues Depending on Resist Removal Processes after Aluminum Etch

The subject of this report is the characterization of plasma etch residues after a metal etch process with Cl2/BCl3 etch gases. One of the interactive factors in the removability of the residues is the photo-mask removal process (DSQ). Depending on the DSQ process the molecular structure of the residues will differ. For our findings, we used laser spectroscopy and Fourier-transformed infrared spectroscopy to obtain information about the degree of the cross-linking of the molecular structure of residues in a post-metal etch cleaning process. The post-etch cleaning is important for removing residues remaining after the metal structuring process. The main goal is to use emission spectroscopy for studying the compounds of the dry-etch related residues. Finally, it was shown that small variations in wafer treatment directly after dry-etching results in different solubilities of residues in HDA (hydroxylamine) based solutions. [1]

Nanoporous oxides of refractory metals: fabrication and properties

AbstractA new approach to fabrication of nanoporous oxides of refractory metals is presented. It is based on the magnetron co‐sputtering of aluminum and refractory metal (titanium, niobium or tungsten) followed by porous electrochemical anodization of the composite film and selective etching of alumina. The nanoporous oxide films with a thickness up to 5 µm were fabricated and studied. The porosity of the oxide films characterized by the surface area of 230 – 460 m2/cm3 can betuned by the aluminum content in the as‐deposited composite films. The pore diameters are found to be varied in nanometer and subnanometer ranges. The parameters of porous titania within porous alumina matrix for different titanium concentrations are presented. The fabricated porous composite oxide films are characterized by the refractive index in the range from 1.45 to 1.77. The dielectric permeability for these films is found to be varied from 6.7 to 24. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Modeling of plasma process data using a multi-parameterized generalized regression neural network

For characterization or optimization process, a computer prediction model is in demand. A new technique, to improve the prediction performance of conventional generalized regression neural network (GRNN) of plasma process data was presented. Genetic algorithm (GA) was applied to optimize multi-parameterized training factors of GRNN. To evaluate the technique, two data sets were collected from the etchings of silica and silicon carbide (SiC) thin films in inductively coupled plasmas. Both data sets called Data I and Data II were statistically characterized by means of 2 3 and 2 4 full factorial experiment plus one center point. The GRNN models trained with these data were tested with additional six and 16 experiments. A total of eight etch outputs were modeled and compared with conventional GRNN and statistical regression models. The five etch outputs comprising Data I include silica etch rate, aluminum (Al) etch rate, Al selectivity, profile angle, and DC bias. Data II consisted of three etch outputs, including SiC etch rate, surface roughness, and profile angle. Compared to GRNN models, GA-GRNN models yielded more than 40% and 15% improvements for all etch outputs comprising Data I and Data II, respectively. Similar improvements were also demonstrated with respect to statistical regression models. All these results reveal that a multi-parameterization of training factors and GA optimization is an effective technique to considerably improve the prediction performance of conventional GRNN model.

Pros and cons of alkaline vs. Acid etching of aluminum: Method chosen boils down to desired appearance and physical attributes of finished product

The chemical milling condition of 2219 aluminum alloy is investigated in the NaOH + Na2S + triethanolamine + Al3+ alkaline system by the assistance of electric currents. The purpose is to study the influences of electric current densities on both the milling rate and the surface roughness of 2219 alloy under different temperatures, NaOH concentrations and additions of inhibitors. The experiments are carried out under the given requirement that the milling rate is from 0.08 mm/min to 0.14 mm/min and the surface roughness is less than 0.65 μm. The reaction temperature of the chemical milling process can be reduced by 10 °C with the application of current densities in the range of 0–20 mA/cm2. The concentration of NaOH in the alkaline system can be reduced from 180 g/L to 120 g/L with the application of current densities in the range of 0–60 mA/cm2. With the addition of Na2SiO3, Na2CO3 and Na2SnO3 inhibitors in the alkaline system, both the milling rate and the surface roughness of 2219 alloy decrease. The region enclosed with the suitable NaOH concentration and current density expands and moves towards the high current density.

Micro-Electro-Mechanical-Systems-Based Infrared Spectrometer Composed of Multi-Slit Grating and Bolometer Array

A micro-electro-mechanical-systems (MEMS)-based IR spectrometer has been designed and fabricated. The proposed micro-spectrometer consists of multi-slit grating and bolometric IR detector array. The grating is used for dispersion of an incident optical radiation into different wavelength components. The grating structure is patterned by reactive ion etching (RIE) of aluminum deposited on dielectric membrane, which is fabricated over silicon wafer. The IR detector part adopts a resistive bolometer that changes its resistance due to the temperature increment. The presence of IR at the specific wavelength can be detected by noticing the resistance change when temperature increases due to an incident IR ray. Vanadium oxide is adopted for resistive bolometer of IR spectrometer in this work because of its higher temperature coefficient of resistance (TCR) which is needed for the better sensitivity. Two parts that composes the MEMS-based IR spectrometer, aluminum multi-slit grating and thermal-type vanadium oxide IR detector, are processed independently and bonded as a final step.

A statistical approach to optimization of alumina etching in a high density plasma

Inductively coupled plasma (ICP) reactive ion etching of Al2O3 with fluorine-based gas chemistry in a high density plasma reactor was carried out in an initial investigation aimed at data storage applications. A statistical design of experiments was implemented to optimize etch performance with respect to process variables such as ICP power, platen power, direct current (dc) bias, and pressure. Both soft photoresist masks and hard metal masks were investigated in terms of etch selectivity and surface properties. The reverse power dependence of dc bias on the ratio of ICP to platen power was elucidated. Etch mechanisms in terms of physical and ion enhanced chemical etchings were discussed. The F-based chemistry greatly enhances the etch rate of alumina compared to purely physical processes such as ion milling. Etch rates as high as 150 nm/min were achieved using this process. A practical process window was developed for high etch rates, with reasonable selectivity to hard masks, with the desired profile, and with low substrate bias for minimal damage.

Growth and passivation of aluminum etch tunnels at on-off controlling DC

In order to control the length of tunnels within Al foil etched in HCl-H2SO4 solutions, the influence of on-off control of the DC on growth and passivation of tunnels has been investigated. From SEM of oxide replicas of tunnels, it was found that, in a given etchant solution at a special temperature, the longest tunnel length depended only on the turn-on interval of DC, and the number of pits was determined by the total electricity of the DC. The corresponding mechanism is that the potential of Al foil changed rapidly at the point of the switch of DC by the result according to the anodic polarization curve and potential-time (E-t) response curves. The moment the DC was switched on, the potential increased immediately over pitting potential, leading to nucleation of pits at the surface and growth of tunnels at special lengths. When the DC was switched off, the potential rapidly decreased to a passive state, leading to the cessation of nucleation and the death of tunnels. Therefore, the longest tunnel length can be controlled and a non-piercing layer can be obtained. Furthermore, consequent etching of Al foil by the on-off control of the DC is beneficial for maintaining a good mechanical strength.