Optimum Etching Conditions Research Articles

Fracture of silicon-rich particles during sliding contact of Al–Si alloys

Fracture of silicon-rich particles (SRP) in a eutectic Al-12% Si alloy during sliding contact by a pyramid indenter was analyzed. The surface of the alloy was subjected to a chemical etching treatment (10% NaOH solution for 420 s) that maximized its wear resistance. SRP were observed to fracture from their roots – the point where the particle's protruded part met the etched aluminum matrix – when the ratio of SRP thickness ( t) to the contact width of the indenter ( W) was less than 1/8 under a normal load of 0.1 N. For large t/ W ratios, particles were resistant to root fracture and exhibited evidence for plastic deformation on their contact surface. The critical particle thickness – below which particle fracture occurred – was shown to depend on the coefficient of friction of the alloy, its matrix hardness and particle fracture toughness. A model for estimating the optimum etching conditions for different SRP morphologies has been developed.

Nanowhiskers formation by radio frequency Ar/O 2 plasma etching of aluminum coated diamond films

Diamond nanowhiskers were fabricated by etching as-grown and aluminum coated diamond films in radio frequency (RF) Ar/O 2 plasma. It was found that diamond nanowhiskers could be obtained by anisotropic etching of both kinds of films. For the as-grown diamond film, the whiskers randomly formed on the diamond surface with higher etching rate. However, for the Al-coated diamond film, an energy dispersive X-ray spectroscopy measurement revealed that the distribution of the whiskers was the same as that of the coated Al particles. During the etching process, Al particles served as masks contributing to restraining the etching of the film underneath. It was found that the distribution of the whiskers was significantly influenced by the Al coating. The whiskers (1 μm in height and 50 nm in diameter) could be obtained under the optimum etching condition. In addition, the dependence of the distribution of the whiskers on Al coating time was demonstrated.

Function of aluminum coating on fabrication of nanowhiskers by radio frequency plasma etching

Diamond nanowhiskers could be obtained by anisotropic etching of as-grown and aluminum coated diamond films in a radio frequency (RF) Ar/O 2 plasma. The distributions of diamond nanowhiskers were on the presence of Al coatings. For the Al-coated diamond film, the distribution of the whiskers was almost same as that of the coated Al particles. However, for the as-grown diamond film, the whiskers randomly formed on the diamond surface with higher etching rate. Comparing these two situations, we found that Al coating was a critical factor in the etching process which served as mask contributing to restraining etching the film underneath. The whiskers (1 μm in height and 50 nm in diameter) could be obtained under optimum etching conditions. In addition, the dependence of the distribution of the whiskers on Al coating time was demonstrated.

Analysis of Photoelectrochemical Processes in α-SiC Substrates with Atomically Flat Surfaces

The etching of α(4H,6H)–SiC{0001} substrates by a photoelectrochemical method using HF (0.015–4.5 wt %) and HF+HNO3 (0.006–1.2 wt %) electrolytes was studied. The dependences of etching rate on polytype, polarity, and pH were measured. In the case of the HF electrolyte, an etching rate of 15–27 nm/min was achieved over a pH range from 0.5 to 4.5 under a photocurrent density of 1 mA/cm2. By optimizing etching conditions, the surface roughness of the Si face could be improved to 0.9 nm (4H) and 0.4 nm (6H) compared with the initial surface roughnesses of 4H (8.9 nm) and 6H–SiC (6.5 nm). In the case of the HF+HNO3 electrolyte, a thin oxide film 2–3 µm thick was formed after 60 min. The oxidized layer was two orders of magnitude thicker than that obtained using the thermal method. The pH of the electrolyte decreased after the electrochemical process, indicating an increase in the concentration of H+ ions. Therefore, holes and H2O have a strong influence on the rate of oxidation reactions in electrochemical methods. Electrochemical etching proceeds by the competitive processes of formation and removal of oxide films.

High density plasma etching of amorphous CoZrNb films for thin film magnetic devices

Inductively coupled plasma reactive ion etching of CoZrNb magnetic thin films was studied using a TiN hard mask in a Cl 2/O 2/Ar gas mix. The etch rates of CoZrNb films and TiN hard mask gradually decreased with increasing Cl 2 or O 2 gas concentrations. When O 2 gas was added in the Cl 2/Ar gas mix, the etch rate of TiN hard mask was suppressed effectively so that the etch selectivity of CoZrNb film to TiN hard mask was enhanced. The addition of O 2 into the gas mix also led to the anisotropic etching of the CoZrNb films and it was confirmed by Auger electron spectroscopy that there were no redeposited materials on the sidewall of the etched films. Highly anisotropic etching of CoZrNb films was achieved at room temperature under the optimized etching conditions.

The Investigation of the Electrolytic Etching Parameters for a Gold Alloy

Abstract Goldsmith has been practiced since as early as 4000 BC but the microstructure examination of precious metals is still an enigma to many metallographers. The precious metal industry, historically secretive, was slow to share technology. In this study, the effects of the electrolytic etching reagents and etching parameters on microstructure for a gold alloy with composition of 91.60 Au – 7.44 Cu – 0.63 Ag – 0.21 Zn – 0.12 Ni (in wt. %) has been investigated. The determination of the optimum etching conditions has been performed using an etching reagent of 32 % HCl.

Optimized condition for etching fused-silica phase gratings with inductively coupled plasma technology

Polymer deposition is a serious problem associated with the etching of fused silica by use of inductively coupled plasma (ICP) technology, and it usually prevents further etching. We report an optimized etching condition under which no polymer deposition will occur for etching fused silica with ICP technology. Under the optimized etching condition, surfaces of the fabricated fused silica gratings are smooth and clean. Etch rate of fused silica is relatively high, and it demonstrates a linear relation between etched depth and working time. Results of the diffraction of gratings fabricated under the optimized etching condition match theoretical results well.

Quantitative control of etching reactions on various SiOCH materials

We have developed a model to predict the process-window length in SiOCH etching using fluorocarbon plasmas (C4F8∕Ar∕O2 and C4F8∕Ar∕N2). The amount of incident reactive particles such as CF2, O, and N radicals were estimated by calculating the partial pressure and dissociation degree of each parent molecule. We have evaluated the relationship between the incident flux and film properties and found that regardless of the film composition and density, the optimum etching condition (Pc) was determined based on the balance between the total C flux and the C removal ability by O and N. Lower concentration of O in SiOCH resulted in a narrow process window because a thick polymer layer formed on the etched surface even under lower CFx flux conditions. In the etching of porous SiOCH film, lower film density increased the etch rate. Because of the narrow process window in the SiOCH etching, the slight change in the incident flux (caused by the aspect ratio or nonuniformity and/or instability of the plasma reactor) induced a great change in the etching properties. In order to fabricate reliable interconnects for next-generation devices, a quantitatively controlled, uniform, and stable plasma system is needed.

Improved Etched Surface Morphology in Electron Cyclotron Resonance-Reactive Ion Etching of GaN by Cyclic Injection of CH4/H2/Ar and O2 with Constant Ar Flow

Electron cyclotron resonance reactive ion etching (ECR-RIE) conditions for GaN using CH4/H2/Ar are investigated. GaN can be etched even with continuous etching using CH4/H2/Ar when Ar gas of a higher flow rate is introduced, but only rough etched surfaces are obtained. A cyclic injection method using CH4/H2/Ar etching gas and O2 ashing with constant Ar flow is introduced for GaN etching for the first time, and a rather high etch rate and very smooth etched surfaces are successfully obtained. The cyclic injection of CH4/H2 and O2 prevents deposition of carbon polymers by oxygen plasma, and constant Ar flow removes the surface oxidized layer formed during the O2 ashing by Ar+ ion etching. Under the optimized etching condition, an etch rate of 34 nm/min and a good morphology of etched surfaces (rms of less than 1.0 nm) are obtained.

GaN-based light-emitting diodes with indium tin oxide texturing window layers using natural lithography

There is a significant gap between the internal and external efficiencies of conventional GaN light-emitting diodes (LEDs). The reason for this shortfall is the narrow escape cone for light in high refractive index semiconductors. In this letter, the p-side-up GaN∕sapphire LEDs with surface textured indium tin oxide (ITO) widow layers were investigated using natural lithography with polystyrene spheres as the etching mask. Under optimum etching conditions, the surface roughness of the ITO film can reach 140 nm while the polystyrene sphere on the textured ITO surface is maintained at about 250–300 nm in diameter. The output power of the ITO∕GaN LED with and without surface texturing is 10.9, and 8.5 mW at 20 mA, respectively. The LEDs fabricated using the surface-textured ITO produced an output power that exceeded that of the planar-surface LED by about 28% at 20 mA.

Thick macroporous membranes made of p‐type silicon

AbstractIn the last decade, very thick macro porous silicon (PS) has been enjoying a growing popularity in a wide range of applications. There is also an increasing demand for thick macroporous membranes with through pores. In this work, we studied the optimal etch conditions with respect to stable pore growth and high etch rate for macro PS in p‐type silicon. A single‐step etching process has been developed to tackle the problem of uniform membrane formation. Very thick (>500 µm) through‐wafer macroporous membranes on p‐type silicon with variable pore sizes and growth rates up to 0.95 µm/min have been successfully demonstrated. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Ridge structure etching of LiNbO3 crystal for optical waveguide applications

A plasma dry etching technique has been applied to the fabrication of LiNbO 3 optical waveguide with a ridge structure for broadband operation. The etching characteristics of a LiNbO 3 single crystal have been investigated according to various ratios of Ar/C 3 F 8 gas mixture. A Ni metal was used as a dry etching mask. The effects of a gas mixture ratio on etching profile angle, sidewall roughness and etching rate were also studied. The etching surface roughness was evaluated by atomic force microscopy (AFM). The etch rate and profile was observed by scanning electron microscopy (SEM). The optimum etching conditions, considering etch rate, profile and surface roughness, were obtained at the 20 sccm C 3 F 8 gas flow.

Fabrication of keyhole-free ultra-deep high-aspect-ratio isolation trench and its applications

An ultra-deep (40–120 µm) keyhole-free electrical isolation trench with an aspect ratio of more than 20:1 has been fabricated. The process combines DRIE (deep reactive ion etch), LPCVD insulating materials refilling and TMAH or KOH backside etching technologies. Employing multi-step DRIE with optimized etching conditions and a sacrificial polysilicon layer, the keyholes in trenches are prevented; as a result the mechanical strength and reliability of isolation trenches are improved. Electrical tests show that such an isolation trench can electrically isolate the MEMS structures effectively from each other and from on-chip detection circuits. The average resistance in the range of 0–100 V is more than 1012 Ω, and the breakdown voltage is above 205 V. This technology has been successfully employed in the fabrication of the monolithic integrated bulk micromachining MEMS gyroscope.

純マグネシウム多結晶体の化学研磨法によるＳＥＭ／ＥＢＳＰ解析試料作製法とその双晶境界の解析

In order to establish a preparation method of pure magnesium samples for OM and SEM/EBSP method, the surfaces of magnesium polycrystal were chemically polished by various solutions. For OM observation and twin observation for SEM/EBSP method, the optimum etching condition was chemical polishing with 20% hydrochloric acid ethanol and 5% nitric acid ethanol. For SEM/EBSP analysis, the optimum etching condition was chemical polishing with a mixture of, nitric acid, hydrochloric acid and dehydrated ethanol of 1 : 2 : 7 in volume ratio. Furthermore, in this study, the crystal orientations of pure magnesium polycrystal treated with above solution were analyzed by SEM/EBSP method. It was found that there are many twins in the samples and all the twins are (1012) type twin. In addition, it was clarified that the orientation relationships between a twin and a neighbor grain and between twins have specific features. When the tip of twin was on boundary, the misorientation of twin and neighbor grain was about 40 degree. When a twin pierced through a grain boundary, the misorientation between twin and neighbor grain was about 75 degree. When twins were crossed each other and the tip of twin touched the other twin, the misorientation of twins was about 60 degree.

Shape Change of Self-Organized NbOx Nanopillar Arrays by High Density Plasma Etching

The fabrication of nanostructures using self-organized niobium oxide nanopillars was investigated by high-density plasma reactive ion etching in a Cl2/Ar gas. Etch rates and etch profiles of niobium oxide pillars were examined by varying etch parameters. We confirmed that several nanostructures, such as nanotip and nanodot arrays, could be fabricated over large areas using optimal anodizing and etching conditions. The mechanism of forming different nanostructures were classified into two groups, isotropic and anisotropic etch mechanisms. It is expected that a novel technique proposed in this study offers a simple and cost-effective method for fabricating nanostructures from various material systems. © 2005 The Electrochemical Society. DOI: 10.1149/1.1990027 All rights reserved.

Chemical synthesis of polypyrrole nano/microstructures using track etch membranes

Among the different strategies to synthesize nanoscopic materials reported in the literature, template synthesis is an elegant approach [1–3]. This technique consists of including metallic or organic constituents inside the void spaces of nanoporous host materials. Though there now exists a huge range of hosts, track-etched membranes present a significant advantage because they lead to the production of different kinds of nanotubules and nanowires with monodisperse diameters and lengths. Martin and Hulteen [4–6] have used these membranes as templates to prepare nanofibrils composed of metals, semiconductors, and conducting polymers, most of their work has focused on the chemical synthesis of polypyrrole, polyaniline, and polymethylthiophene. In the present work, the chemical growth of polypyrrole nanofibrils obtained from polycarbonate nanoporous particle track-etched membranes is studied. The morphologies of the obtained microstructures have been carefully analyzed using a scanning electron microscope. A two-probe method has been used to measure the electrical conductivity of template-synthesized polypyrrole microstructures. The nuclear track filter used here as a template was of Makrofol KG foil (polycarbonate from Bayer AG), 60 μm thick, having average pore diameter ∼ 6 μm with pore density 1 × 106 m−2. This was prepared by irradiating the foil with 238U, energy ca. 13.64 MeV/n at 90 ◦C at the UNILAC facility available at GSI, Darmstadt, Germany, followed by chemical amplification of the damage trails by etching in 6N NaOH, at 60 ± 2 ◦ C for 35 min. In order to produce see-through pores, optimum etch time and etch conditions were preset. As shown in Fig. 1, the polycarbonate membrane was used as a dividing wall in a two-compartment cell. In the first compartment, an aqueous pyrrole solution (0.5 M) was added and allowed to diffuse through the membrane for 10 min prior to the introduction of the oxidant reagent ferric chloride (0.4 M) in the second compartment. The monomer and the oxidant reagent diffuse toward each other through the pores of the membrane and react to yield the polymer. The polymerization process was continued for 1 hr 30 min. For the morphological characterization of the polypyrrole microstructures by means of scanning electron microscopy (SEM), specimens were observed by dissolving the polycarbonate matrix in dicholoromethane. The cleaned and dried samples were mounted on the specially designed aluminum stubs with the help of double sided adhesive tape and viewed under a “Jeol, JSM 6100 Scanning Microscope” at an accelerating voltage of 20 KV. Images were recorded on the photographic film in the form of negatives at different magnifications. Fig. 2 shows scanning electron micrographs of polypyrrole microstructures. Fig. 3 shows a scanning electron micrograph of a single polypyrrole microtube. The electrical conductivity of the polypyrrole microstructures established inside the pores was obtained by measuring the bulk resistance across the filled membrane by a two-probe method. Since the polypyrrole surface layers on the membrane can contribute to the resistance measurement but cannot be completely removed because they ensure the contact between the polypyrrole nanostructures and electrical wires [7], we tried to limit the thickness of these surface layers. Cai et al. [7] indicated that such thin layers did not contribute to the membrane resistance. One side of the membrane was held on the copper electrode and two copper wires contacted the other side of the membrane. Silver paste ensured a good contact and allowed specification of a well-defined crosssection for calculating the conductivity. The conductivity along a single fiber can be calculated from the resistance measurement that provides the bulk resistance of the composite membrane. Assistance R can be written as

The effect of SiCl4 additive gas on the Cl-based Al plasma etch procedure

The influences of both SiCl4 additive gas and the magnitude of bias voltage on the anisotropic etch profile of aluminum pattern and the deterioration of photoresist (PR) mask layer have been studied by varying etching conditions. Using Cl2 gas as a primary etchant, the ratio of SiCl4 flow rate to Cl2 and the ion energy bombarded onto the surface were changed systematically. When a small amount of additive gas was added, undercut profile in Al layer was not observed even in the lowest bias voltage measured in this experiment. With the optimized etching condition, the PR deterioration usually reported during metal etching was not observed at all, which allows the complete PR strip without any additional process.

Reducing Photocurable Polymer Pattern Shrinkage and Roughness during Dry Etching in Photo-Nanoimprint Lithography

When we apply a photocurable polymer to photo-nanoimprint lithography, dry etching is necessary to remove the remaining photocurable polymer after imprinting. During dry etching, it is necessary to achieve pattern profiles with small pattern shrinkage, smooth surface, and low edge roughness. Room-temperature etching resulted in serious pattern shrinkage, but this was markedly reduced by substrate cooling (temperature -120°C). We obtained pattern shrinkage ranging from a maximum of 23 nm to a minimum of 4 nm under optimum etching conditions. We found that the surface of the photocurable polymer became rough and a large amount of polymer residue still remained after removing the remaining photocurable polymer. We obtained a smooth substrate surface by increasing both the RF power and total flow rate of the SF6/O2 gas mixture. Under optimum etching conditions, we obtained fine etch profiles of the photocurable polymer with a surface roughness of 2.5 nm, reduced pattern shrinkage, and a 3 nm line edge roughness.

Effect of environmental conditions on radon concentration-track density calibration factor of solid-state nuclear track detectors

In this work, the effect of environmental conditions viz., temperature (T) and relative humidity (RH) on the track density-radon concentrations calibration factor (K) has been studied for CR-39 and LR-115 track detectors. The factorK was determined using a reference radon chamber in the National Institute for Standards (NIS) in Egypt. Track detectors were etched at the recommended optimum etching conditions.

圧電薄膜を利用する浮上量制御型アクティブスライダに関する研究(情報機器コンピュータメカニクス2 -機構・制御,IIP2004 情報・知能・精密機器部門講演会)

This paper describes a novel active head slider equipped with micro-actuator using PZT thin films for flying height control. The active head slider is a breakthrough technology for achieving ultra-low spacing of less than 10nm. The position of a read/write magnetic head is gone above and below because an unimorph cantilever build in the slider bends by PZT thin film, and flying height is controlled. The multi-step silicone etching process by ICP-RIE or RIE is important to fabricate active head sliders. Therefore, the fabrication process of a silicone slider structure was completed by optimizing etching conditions.