Showing papers on "Hydrofluoric acid published in 2005"

Hydrogen passivation of germanium (100) surface using wet chemical preparation

Abstract: A wet chemical preparation involving de-ionized water, hydrogen peroxide, and hydrofluoric acid is used to passivate germanium (Ge) (100) surfaces. Infrared absorption spectroscopy and x-ray photoemission spectroscopy studies show that oxide free and hydrogen-terminated Ge (100) surfaces can be obtained. As in the case for silicon (100) surfaces etched in hydrofluoric acid, hydrogen-terminated Ge (100) surfaces are atomically rough, with primarily mono- and dihydride terminations.

Ionic Liquid and Solid HF Equivalent Amine-Poly(Hydrogen Fluoride) Complexes Effecting Efficient Environmentally Friendly Isobutane−Isobutylene Alkylation

Abstract: Isoparaffin−olefin alkylation was investigated using liquid as well as solid onium poly(hydrogen fluoride) catalysts. These new immobilized anhydrous HF catalysts contain varied amines and nitrogen-containing polymers as complexing agents. The liquid poly(hydrogen fluoride) complexes of amines are typical ionic liquids, which are convenient media and serve as HF equivalent catalysts with decreased volatility for isoparaffin−olefin alkylation. Polymeric solid amine:poly(hydrogen fluoride) complexes are excellent solid HF equivalents for similar alkylation acid catalysis. Isobutane−isobutylene or 2-butene alkylation gave excellent yields of high octane alkylates (up to RON = 94). Apart from their excellent catalytic performance, the new catalyst systems significantly reduce environmental hazards due to the low volatility of complexed HF. They represent a new, “green” class of catalyst systems for alkylation reactions, maintaining activity of HF while minimizing its environmental hazards.

Stress control in masking layers for deep wet micromachining of Pyrex glass

Abstract: In this paper, we report three etching masking technologies of Cr/Au, Cr/Cu and PECVD amorphous silicon developed for Pyrex glass micromachining in hydrofluoric acid solution. Our study reveals that the residual stress, especially the tensile stress, in the mask layers is responsible for the pinholes on the glass surface and notch defects on the edge formed at the etch edges of glass due to the breakage of highly stressed mask layers during the etching process. The Cr/Au metal mask can achieve a glass etch depth up to 100 μm, along with a number of pinholes and notch defects on the edge due to the high tensile residual stress in the Cr/Au layer. The Cr/Cu metal masking layer improves the glass etch quality by the reduced residual stress. Detailed studies have been done using the amorphous silicon film as a glass etch mask. The PECVD process and the subsequent annealing process have been optimized to reduce the compressive residual stress in the amorphous silicon layer. The maximum etch depth in the glass can be as high as 200 μm and almost without pinholes and notch defects on the edge. To our knowledge, this is the best result reported in the literature so far.

Why is hydrofluoric acid a weak acid

Abstract: The infrared vibrational spectra of amorphous solid water thin films doped with HF at 40K reveal a strong continuous absorbance in the 1000–3275cm−1 range. This so-called Zundel continuum is the spectroscopic hallmark for aqueous protons. The extensive ionic dissociation of HF at such low temperature suggests that the reaction enthalpy remains negative down to 40K. These observations support the interpretation that dilute HF aqueous solutions behave as weak acids largely due to the large positive reaction entropy resulting from the structure making character of the hydrated fluoride ion.

Rapid, Micro-Methods to Estimate Plant Silicon Content by Dilute Hydrofluoric Acid Extraction and Spectrometric Molybdenum Method

Abstract: By treating 0.5 g DW of a plant sample directly with 10 ml of a dilute hydrofluoric acid solution (HF solution, 1.5 M HF—0.6 M HCl), all the silica in plant (as much as 150 mg SiO2) was dissolved within 1 h. After dilution of the extract with 40 mL of distilled water, the silica in the extract was measured by the spectrometric molybdenum yellow method. The molybdenum yellow method, in which silica in 0.1 mL of the diluted extract can be determined in 8 min, is well suited to rapid, micro-estimations of the silica content in plants. In the micro-modification, the size of the plant sample was reduced to 100 mg DW. The analytical procedure was simple, and the analytical time was less than 2 h. The method can save much labor and time, compared with the gravimetric analysis. The dissolution with HF solution and the molybdenum yellow method were also applied to the measurement of the content of silica separated by acid digestion of rice plants. Excellent agreement in the silica measurement of rice plants was co...

METHOD FOR PREPARING FLUORINE BY ELECTROLYZING HYDROFLUORIC ACID USING NICKEL CONTAINING 0.01 wt.% OR LESS OF CARBON AND HAVING PURITY OF 99.8% OR MORE AS ANODE MATERIAL

Abstract: PURPOSE: To prepare fluorine gas containing 10 ppm or less of carbon tetrafluoride(CF4) as an impurity industrially inexpensively by changing a conventional carbon electrode into a nickel electrode containing 001 wt% or less of carbon and having purity of 998% or more CONSTITUTION: In a method for preparing fluorine by electrolyzing hydrofluoric acid(HF), a preparation method of high purity fluorine is characterized in that nickel containing 001 wt% or less of carbon and having purity of 998% or more is used as an anode material, wherein electrolysis is performed by impressing electric current to the electrolyte after putting the nickel anode and a nickel or stainless steel cathode into an electrolyte containing hydrofluoric acid and alkali metal salt thereof in a mole ratio range of 15 to 3:1, wherein prepared fluorine has a purity of 99999% or more, and content of carbon tetrafluoride is 10 ppm or less, and wherein the prepared fluorine is reacted with ammonia(NH3) or ammonium fluoride to prepare nitrogen trifluoride(NF3)

First Structural Characterization of a Protactinium(V) Single Oxo Bond in Aqueous Media

Abstract: The present work describes the first structural studies of protactinium(V) in sulfuric and hydrofluoric acid media using X-ray absorption spectroscopy. The results show unambiguously the absence of the trans-dioxo bond that characterizes the other early actinide elements such as U and Np. In concentrated sulfuric acid (13 M), Pa(V) is proved to exhibit a single oxo bond as postulated in the literature for species in more dilute media. In a 0.5 M HF medium, XANES and EXAFS spectra indicate the absence of any oxo bond: Pa(V) exists in the form of a pure fluoro complex.

Synthesis of luminescent silicon nanopowders redispersible to various solvents.

Abstract: Silicon nanopowder with a narrow size distribution was synthesized by a simple method, in which amorphous SiOx (x < 2) powder as starting material was annealed at high temperature and then etched by hydrofluoric acid (HF). Si nanoparticles thus obtained exhibited emission in the ultraviolet and visible regions under excitation at an energy corresponding to the direct band-gap transition. At the same time, they could be redispersed in various organic solvents such as octanol, toluene, etc., without surfactants or capping molecules on particle surfaces. X-ray diffraction and Fourier transform infrared spectroscopy were used to follow the change of components in the sample during annealing and HF etching processes, and the size distribution and dispersion morphology of the nanoparticles in different solvents were revealed by transmission electron microscopy analysis.

3-Hydroxybenzoic acid as AISI 316L stainless steel corrosion inhibitor in a H2SO4-HF-H2O2 pickling solution

Abstract: 3-Hydroxybenzoic acid (3-HBA) was studied for possible use as a AISI 316L stainless steel (SS) corrosion inhibitor in an environmental-friendly aqueous pickling solution of 75 g l−1 sulphuric acid (H2SO4), 25 g l−1 hydrofluoric acid (HF) and 30 g l−1 hydrogen peroxide (H2O2). 3-HBA was tested in concentrations from 5 × 10−5 to 5 × 10−1M at 298 and 313 K temperature. Inhibition efficiency increased with the 3-HBA concentration. The inhibitor mechanism is discussed in terms of the properties of the isotherm equations of Frumkin, Hill-de Boer and Kastening–Holleck mainly. The shape, the trend of the slopes along the curve and the existence of inflection points, were analysed as the characteristics that differentiate one adsorption equation from another. The best fit was obtained using the Frumkin isotherm model. The projected molecular area of 3-HBA was calculated as a structural parameter to elucidate its optimal inhibition mechanism.

Methods of forming semiconductor constructions and capacitors

Abstract: The invention includes methods in which silicon is removed from titanium-containing container structures with an etching composition having a phosphorus-and-oxygen-containing compound therein. The etching composition can, for example, include one or both of ammonium hydroxide and tetra-methyl ammonium hydroxide. The invention also includes methods in which titanium-containing whiskers are removed from between titanium-containing capacitor electrodes. Such removal can be, for example, accomplished with an etch utilizing one or more of hydrofluoric acid, ammonium fluoride, nitric acid and hydrogen peroxide.

Synthesis of LaMeO3 (Me = Cr, Mn, Fe, Co) Perovskite Oxides from Aqueous Solutions

Abstract: LaMeO{sub 3} (Me = Cr, Mn, Fe, Co) perovskite oxides have many functional uses, and methods for forming films from aqueous solutions are advantageous compared with CVD, sputtering, sol-gel methods, etc., because of lower cost, no requirement for a vacuum or high temperature, and applicability to films with wide areas and/or complicated shapes. A novel method for synthesizing LaMeO{sub 3} from aqueous solutions at ordinary temperature and pressure has been discovered. LaMeO{sub 3} powder produced by solid-state reaction was dissolved in hydrofluoric acid. Boric acid was added to shift the chemical equilibrium, then LaMeO{sub 3} was synthesized. This method promises to lead to applications for preparing perovskite films for various uses.

Manufacturing method of semiconductor device

Abstract: PROBLEM TO BE SOLVED: To prevent voids (cavities) from being generated in the sidewalls of a trench and contact hole formed in a porous insulating film, in the manufacturing method of a semiconductor device having the porous insulating film. SOLUTION: When so etching an interlayer insulating film 5 including a porous low dielectric-constant film 3a as to form a contact hole 7a, fluorine A remains in the inside of the porous low dielectric-constant film 3a which is present near a sidewall 3b of the contact hole 7a, because of the use of a fluorine-based gas. When the fluorine remains therein, the fluorine is so dissolved in a water by the rinsing of a cleaning process performed thereafter, etc., and is so changed into a hydrofluoric acid as to generate voids in after-processes by etching the porous low dielectric-constant film 3a. Therefore, in order to remove the residual fluorine A, a semiconductor substrate 1 is irradiated from above it by a hydrogen radical B after forming the contact hole 7a. Then, the fluorine A is so substituted by a gaseous hydrofluoric acid C as to be able to remove the fluorine A without etching the porous low dielectric-constant film 3a. COPYRIGHT: (C)2005,JPO&NCIPI

Method for preparing polycrystalline silicon suede

Abstract: The pile fabrics of polycrystalline silicon wafer are made by using acid corrosion solution. The acid corrosion solution is a mixed liquor of oxidant and hydrofluoric acid. The concentration range of oxidant is 0.01-0.5 mole/ liter. The concentration range of hydrofluoric solution is 1-15 mole/liter. The temperature range is 5-50deg.C. The range of acid corrosion time is 5-60 min.

Fabrication of porous membrane filter from p-type silicon

Abstract: Macropore formation and applications of low-doped p-type silicon have been studied. Traditional hydrofluoric acid/ethanol/water electrolyte and organic electrolytes containing dimethyl sulfoxide and hydrofluoric acid were used, and different anodization current densities were applied in order to optimize the pore formation and prevent cracking of the layer. Thin crystalline membranes were prepared by anisotropic wet etching from the backside, using a silicon nitride layer as a mask. A similar silicon nitride layer was used to define the area of the membrane to be porosified. Macroporous silicon membranes have been fabricated and tested as a filter for biomedical samples. Fluorescently labeled polystyrene beads, 1 μm in diameter, were succesfully used to demonstrate filter action.

Fabrication of porous membrane filter from p-type silicon

Abstract: Macropore formation and applications of low-doped p-type silicon have been studied. Traditional hydrofluoric acid/ethanol/water electrolyte and organic electrolytes containing dimethyl sulfoxide and hydrofluoric acid were used, and different anodization current densities were applied in order to optimize the pore formation and prevent cracking of the layer. Thin crystalline membranes were prepared by anisotropic wet etching from the backside, using a silicon nitride layer as a mask. A similar silicon nitride layer was used to define the area of the membrane to be porosified. Macroporous silicon membranes have been fabricated and tested as a filter for biomedical samples. Fluorescently labeled polystyrene beads, 1 μm in diameter, were succesfully used to demonstrate filter action.

Sb(III) fluoride complexes with DL-valine. Crystal structure of molecular complex SbF 3 {(CH 3 ) 2 CHCH( + NH 3 )COO − }

Abstract: Preparative method in combination with X-ray diffraction and IR spectroscopy is used to study reaction of Sb(III) fluoride with α-aminoisovaleric acid (DL-valine) in an aqueous solution in the range of the molar ratios of components (0.25–2) : 1 in the presence of hydrofluoric acid. The molecular complex of Sb(III) fluoride with valine (1 : 1) of the composition SbF3{(CH3)2CHCH(+NH3)COO−}(I) and valinium tetrafluoro-antimonate(III) monohydrate {(CH3)2CHCH(+NH3)COOH}SbF4· H2O (II) are synthesized for the first time. Crystal structure was determined for the molecular complex I consisting of SbF3 groups and valine molecules united into polymer chains through bidentate bridging carboxylate groups of amino acid molecules.

System and method for pre-gate cleaning of substrates

Abstract: A system and method for cleaning semiconductor wafers wherein the use of SCI and SC2 is eliminated and replaced by the use DIO3 and dilute chemistries. In one aspect, the invention is a method comprising: (a) supporting in a process chamber at least one semiconductor wafer having a silicon foundation with a silicon-dioxide layer in at least one pre-gate structure; (b) applying an aqueous solution of hydrofluoric acid in deionized (DI) water to the semiconductor wafer to remove the silicon dioxide layer and form a gate; (c) applying ozonated deionized water (DIO3) to the semiconductor wafer to remove particles from the gate and passivate the silicon foundation; (d) applying a dilute solution of hydrofluoric acid and hydrochloric acid in DI water to the semiconductor wafer to remove any silicon dioxide layer that may have formed in the gate from the application of the DIO3 and to remove any metal contaminants; and (e) applying DIO3 to the semiconductor wafer to grow a new layer of silicon dioxide on the silicon foundation in the gate.

Etching solution for removal of oxide film, method for preparing the same, and method of fabricating semiconductor device

Abstract: Provided are an anionic surfactant-containing etching solution for removal of an oxide film, preparation methods thereof, and methods of fabricating a semiconductor device using the etching solution. The etching solution includes a hydrofluoric acid (HF), deionized water, and an anionic surfactant. The anionic surfactant is a compound in which an anime salt is added as a counter ion, as represented by R 1 —OSO 3 − HA + , R 1 —CO 2 − HA + , R 1 —PO 4 2− (HA + ) 2 , (R 1 ) 2 —PO 4 − HA + , or R 1 —SO 3 − HA + where R 1 is a straight or branched hydrocarbon group of C 4 to C 22 and A is ammonia or amine. The etching solution provides a high etching selectivity ratio of an oxide film to a nitride film or a polysilicon film. Therefore, in a semiconductor device fabrication process such as a STI device isolation process or a capacitor formation process, when an oxide film is exposed together with a nitride film or a polysilicon film, the etching solution can be efficiently used in selectively removing only the oxide film.

Method of preparing nano-silicon carbide fiber

Abstract: The invention discloses a method of preparing nano-silicon carbide fiber consisting of dissolving phenolic resin into absolute ethyl alcohol, charging rare-earth metal nitrate, acetate or chloridate to make it dissolved, dropping tetra ethyl ortho silicate into the solution, charging oxalate and hydrochloric acid, hydrolyzing at room temperature to obtain the carbon-silicon dyadic colloidal sols, charging hexamethylenetetramine, drying to obtain xerogel, elevating the temperature of the xerogel to 1200-1400 deg. C in argon gas protective atmosphere, cooling down to room temperature, subjecting the reaction product to air oxidation, expelling the non-reacted rare earth metallic oxide and silicon dioxide with nitric acid and hydrofluoric acid, finally washing, filtering, and drying to obtain the silicon carbide nano fiber.

Method for evaluating crystal defects of silicon wafer

Abstract: A method for evaluating crystal defects of a silicon wafer comprising: etching a surface of the silicon wafer by immersing the wafer in an etching solution; and observing etch pits formed on the etched surface of the wafer, wherein the silicon wafer of which crystal defects are evaluated has low electrical resistivity of 1 Ω·cm or less, and the etching solution is a mixture of hydrofluoric acid, nitric acid, acetic acid and water further including iodine or iodide, in which a volume ratio of nitric acid in the etching solution is the largest among volume ratios of hydrofluoric acid, nitric acid, acetic acid and water, and the etching solution is adjusted to have an etching rate of 100 nm/min or less for the silicon wafer. Thereby, there is provided a method for evaluating crystal defects of a silicon wafer with low electrical resistivity by using a chromium-free etching solution without toxic chromium with high capability of detecting defects.

Measurement of inorganic acidic gases and particles from the stack of semiconductor and optoelectronic industries

Abstract: A method for sampling inorganic acids in the exhaust gas of semiconductor and optoelectronic industries was developed by using a porous metal denuder and an ion chromatograph analysis. The sampler consists of a Teflon filter to collect inorganic acidic aerosols followed by two coated porous metal discs for sampling inorganic acidic gases. The second disc was used to check if the gas broke through the first disc. The method detection limit of the sampler is appropriate for sampling the exhausted gas at semiconductor or photoelectric industries. Test results indicated that the calibration curves had good coefficients of correlation, and the concentrations of the laboratory and field blanks were found to be lower than the method detection limit. For the semiconductor and optoelectronic industries, the total concentration of acidic gases and particles for hydrofluoric acid, hydrochloric acid, nitric acid, phosphoric acid, and sulfuric acid was found to be 85–999, 40–820, 21–223, ND (not detectable)–4...

Optimization and performance analysis of copper immersion coating on AZ91 magnesium alloy

Abstract: An orthogonal experimental methodology was used to study a copper immersion coating on AZ91 magnesium-alloy from a hydrofluoric acid-containing bath. Factors such as hydrofluoric acid concentration, sonication time, chemical etching, and activation process were considered in the design. The analysis of variance on the orthogonal experimental results was performed, resulting in an optimal condition for achieving a uniform copper coating with high coverage. Hydrofluoric acid was found to be an essential component in the copper immersion coating bath and a possible mechanism was suggested to explain its significance in terms of magnesium film destruction and magnesium dissolution.

Polishing and deburring composition for workpieces of carbon steel and method of chemical polishing and deburring

Abstract: Polishing and deburring agent (A) for work pieces of carbon steel comprises hydrogen peroxide, hydrofluoric acid and at least a stabilizer for hydrogen peroxide, where the: amount of the hydrofluoric acid is 0.1-10 wt.%, molar ratio of the hydrofluoric acid to hydrogen peroxide is 0.1-1.4 and agent is free of ammonium. An independent claim is included for a method for chemical polishing and deburring of workpiece of carbon steel comprising immersing the workpiece of carbon steel (with a carbon content of up to 1.5 wt.%) in (A) and maintaining at a predetermined impact time.

Process for preparing titanium silicon carbon ceramic powder

Abstract: The invention provides a process for preparing titanium silicon carbon ceramic powder which comprises the steps of, (1) mixing titanium (Ti), silicon (Si), graphite powder (C) by the mol ratio of 3 : (1-2) : (15-2), ball grinding to synthesize ceramic powder with Ti, Si and C as the principal phase, (2) acid-washing the synthesized fines 05-2 hours through hydrofluoric acid solution to remove the silicides, (3) subjecting the powder to distilled water rinsing and drying, oxidation treating 1-4 hours at 400-500 deg C to remove titanium carbide, removing the oxides by using the mixed solution of ammonia sulfate and sulfuric acid, water scrubbing and drying to obtain the Ti-Si-C ceramic powder