HCl Cleaning Research Articles

Evaluation of chemical cleaning of UF membranes fouled with whey protein isolates via analysis of residual protein components on membranes surface

Cleaning of membranes fouled with protein solutions is a common part of the normal operational procedure in membrane applications for the dairy and other food industries. Chemical cleaning with simple caustic and acid cleaners is still common practice although the response of different protein components in a foulant layer to cleaning agents is not well understood. This paper examines the efficiency of chemical cleaning of polyethersulfone (PES) membranes fouled during ultrafiltration of whey protein isolates solution and the protein residuals remaining on the membranes after cleaning. Using a combination of the Lowry assay and gel-electrophoresis for estimation of protein amount and composition on the membrane before and after cleaning, it was observed that the high molecular weight components in the foulant layer could more easily be removed than the smaller components, and the proteins trapped in the membrane pores were the most difficult to clean. In repeated cycles of filtration and cleaning with NaOH followed by HCl, the flux recovery due to NaOH cleaning remained constant after the 2nd cycle, while the flux recovery due to HCl cleaning increased with the repeated cycle, indicating the importance of HCl cleaning stage in the removal of residual protein components.

Native Oxidation Growth on Ge(111) and (100) Surfaces

We studied the native oxide growth on Ge(100) and (111) surfaces treated by HCl and HF cleaning in clean room air by high-resolution X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry (SE). The native oxidation of both HCl- and HF-last Ge(100) surfaces exhibited likely layer-by-layer fashion. The native oxide growth of the n-Ge(100) was significantly faster than the p-Ge(100) at the early stage of native oxidation. This can be explained by the formation of an O2- ion through free electron transfer from the Ge to the adsorbed O2 molecules, which induces the surface electric field that can initiate the oxidation. In the case of different crystallographic orientations, the oxide rate of the Ge(100) surface was faster than that of the Ge(111) surface. This might be attributed to larger open space of the Ge(100) surface than that of the Ge(111) surface.

Native Oxidation Growth on Ge(111) and (100) Surfaces

We studied the native oxide growth on Ge(100) and (111) surfaces treated by HCl and HF cleaning in clean room air by high-resolution X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry (SE). The native oxidation of both HCl- and HF-last Ge(100) surfaces exhibited likely layer-by-layer fashion. The native oxide growth of the n-Ge(100) was significantly faster than the p-Ge(100) at the early stage of native oxidation. This can be explained by the formation of an O2- ion through free electron transfer from the Ge to the adsorbed O2 molecules, which induces the surface electric field that can initiate the oxidation. In the case of different crystallographic orientations, the oxide rate of the Ge(100) surface was faster than that of the Ge(111) surface. This might be attributed to larger open space of the Ge(100) surface than that of the Ge(111) surface.

Study of the surface cleaning of GOI and SGOI substrates for Ge epitaxial growth

An effective wet cleaning process, optimized for low temperature Ge epitaxial growth on thin Ge or SiGe structures with reduced surface roughening, is proposed. It is found that HF + HCl cleaning is the most effective wet cleaning method that is applicable to the low temperature thermal cleaning. It is also found that temperature of the thermal cleaning appropriate to 25–30 nm thick germanium on insulator (GOI) or silicon–germanium on insulator (SGOI) substrates is approximately 450 °C. Moreover, it is also found that the temperatures of Ge epitaxial growth even in lattice-matched systems must be reduced to around 400 °C to prevent surface roughening and those in lattice-mismatched systems also must be reduced sufficiently (300 °C for strained Ge growth on SGOI ( X eff = 0.6)) to prevent lattice relaxation as well as surface roughening. Finally, the successful formation of the compressively strained GOI structures is demonstrated by applying these wet cleaning and low temperature thermal cleaning processes and low temperature Ge epitaxy to thin SGOI substrates.

Inversion-Mode Self-Aligned $\hbox{In}_{0.53}\hbox{Ga}_{0.47}\hbox{As}$ N-Channel Metal-Oxide-Semiconductor Field-Effect Transistor With HfAlO Gate Dielectric and TaN Metal Gate

A high-performance In0.53Ga0.47As n-channel MOSFET integrated with a HfAlO gate dielectric and a TaN gate electrode was fabricated using a self-aligned process. After HCl cleaning and (NH4)2S treatment, the chemical vapor deposition HfAlO growth on In0.53Ga0.47As exhibits a high-quality interface. The fabricated nMOSFET with a HfAlO gate oxide thickness of 11.7 nm shows a gate leakage current density as low as 2.5 times 10-7 A/cm2 at Vg of 1 V. Excellent inversion capacitance was illustrated. Silicon implantation was self-aligned to the gate, and low-temperature activation for source and drain was achieved by rapid thermal annealing at 600degC for 1 min. The source and drain junction exhibited an excellent rectifying characteristic and high forward current. The result of an In0.53Ga0.47As nMOSFET shows well-performed Id-Vd and Id-Vg characteristics. The record high peak electron mobility of 1560 cm2/Vs has been achieved without any correction methods considering interface charge and parasitic resistance.

The effectiveness of HCl and HF cleaning of Si0.85Ge0.15 surface

The cleaning of Si0.85Ge0.15 surfaces using HCl and HF solutions is studied using synchrotron radiation photoelectron spectroscopy. The HF solution is found to be effective in removing both the Si oxide and the Ge oxide while the HCl solution can only remove part of the Ge oxide. For samples treated with HF, four spectral components are needed to fit the Ge 3d photoemission spectra. One is the bulk component and the other three are attributed to the surface Ge atoms with monohydride, dihydride, and trihydride terminations, respectively.

Metamorphic In0.53Ga0.47As Metal–Oxide–Semiconductor Structure on a GaAs Substrate with ZrO2 High-k Dielectrics

The electrical properties of metamorphic In0.53Ga0.47As metal–oxide–semiconductor capacitors with a 100-Å-thick ZrO2 layer as high-k dielectrics were investigated. The In0.53Ga0.47As surface was pretreated by either sulfur passivation or HCl cleaning before the ZrO2 deposition. Owing to the lower interface-state density after sulfidation, the sulfur-passivated capacitor exhibited better accumulation capacitance and strong inversion at capacitance–voltage measurement than the HCl-cleaned capacitor after post deposition annealing at 350 °C. On the basis of material analyses, the capacitors that subjected to underwent sulfur treatment were found to acquire a thin sulfur layer on the interface, which protects their surface from air exposure and prevents performance degradation.

Hf O 2 gate dielectric on (NH4)2S passivated (100) GaAs grown by atomic layer deposition

The interface between hafnium oxide grown by atomic layer deposition and (100) GaAs treated with HCl cleaning and (NH4)2S passivation has been characterized. Synchrotron radiation photoemission core level spectra indicated successful removal of the native oxides and formation of passivating sulfides on the GaAs surface. Layer-by-layer removal of the hafnia film revealed a small amount of As2O3 formed at the interface during the dielectric deposition. Traces of arsenic and sulfur out diffusion into the hafnia film were observed after a 450°C postdeposition anneal and may be the origins for the electrically active defects. Transmission electron microscopy cross section images showed thicker HfO2 films for a given precursor exposure on sulfur treated GaAs versus the nontreated sample. In addition, the valence-band and the conduction-band offsets at the HfO2∕GaAs interface were deduced to be 3.18eV and a range of 0.87–1.36eV, respectively. It appears that HCl+(NH4)2S treatments provide a superior chemical passivation for GaAs and initial surface for atomic layer deposition.

Etching of GaAs substrates to create As-rich surface

Several different cleaning procedures for GaAs (100) substrates are compared using X-ray photoelectron spectroscopy and optical microscopy. This work emphasizes the effect of the last etching step: using either HCl, HF-ethanol (5%) or static deionized water after HCl cleaning. All the procedures except HCl solution (1:1) produce an As-rich surface. Also, none of the etchants except HF-ethanol solution produce Ga or As-rich (oxide free) surfaces. Optical microscopic study shows different etch pits produced due to etching in different solutions.

Characteristics of Membrane Fouling in an Anaerobic-(Anoxic/Oxic)n-MBR Process

Abstract The characteristics of membrane fouling and cleaning, in a hybrid MBR process, was investigated. Under the condition of sub-critical flux operation, a characteristic three-stage trans-membrane pressure (TMP) profile is observed as time passes. The initially extended period of slow pressure rise, followed by a somewhat faster rise, is then supplanted by a sudden transition to rapid pressure rise. Membrane cleaning experiments and SEM examination make it apparent that the rapid TMP rise is mainly caused by the accumulation of a surface cake layer, which is a reversible fouling that can be removed by tap water washing. Fouling caused by a gel layer, which is an irreversible fouling, can be removed efficiently by chemical cleaning. NaClO can oxidize the gel layer, which is formed mainly of macro-molecular organic substances. The HCl can remove inorganic particles formed by Ca 2+ , Mg 2+ ions etc. The sequence of chemicals used in membrane cleaning has an influence on the cleaning result. The effect of the NaClO+HCl cleaning procedure is superior to that of the HCl+NaClO one. Particle size distribution measurements (PSD) reveal that fine particles are inclined to deposit or attach on the membrane surface, or in the membrane pores, and caused rapid fouling.

Copper bonded layers analysis and effects of copper surface conditions on bonding quality for three-dimensional integration

In order to achieve copper wafer bonding with good quality, surface conditions of copper films are important factors. In this work, the effects of surface conditions, such as surface roughness and oxide formation on the bond strength, were investigated under different bonding conditions. Prior to bonding, copper film surfaces were kept in the atmosphere for less than 1 min, 3 days, and 7 days, respectively, to form different thicknesses of oxide on the surface. Some copper wafers were cleaned using HCl before bonding in order to remove the surface oxide. Surface roughness of copper films with and without HCl cleaning was examined. Since surface cleaning before bonding removes oxides but creates surface roughness, it is important to study the corresponding bond strength under different bonding conditions. These results offer the required information for the process design of copper wafer bonding in three-dimensional integration applications.

Sensitive, selective, and analytical improvements to a porous silicon gas sensor

Conductometric porous silicon gas sensors consisting of a sensitive surface layer which is conducive to the rapid and reversible transduction of sub-ppm levels of analyte gas have been developed. Several new fabrication and testing methods allow the detection of a number of analytes including CO (<5 ppm), NO x (<1 ppm), SO 2 (<1 ppm), and NH 3 (500 ppb). We outline a progression of fabrication techniques, including an HCl cleaning process, which allow the formation of much more efficient porous silicon sensors. Selectivity and enhanced sensitivity are developed using electroless metal deposition to form a gold or tin oxide nanostructured framework interacting with the nanopore-coated microporous surface. The ability to monitor sensor response in the presence of external noise sources is increased with the introduction of an FFT filtering technique. These studies present the first detection of CO with a porous silicon sensor as well as a considerable improvement in the sensitivity to NH 3. It is suggested that a diffusion-based model can be used to parameterize the response of the sensors. We demonstrate several applications of these sensors to the monitoring of gas mixtures as exemplified by the NH 3/NO x system. The potential for these sensors in arrayed configurations with integrated CMOS devices is considered.

錫含浸法によるリサイクルＷＣ微粒子を用いた再生超硬合金の物性

In this experiment, the development of recycling method at cemented carbide scraps was researched. First, brittle alloy was obtained by tin impregnation method and then WC fine powder was procured after the physical crushing. Thereafter, the sample followed by the processes of reduction treatment, molding and sintering works. Some properties of recycled cemented carbides were investigated. The results summarized as follows; Recycled WC fine powder suffered the surface oxidation. Therefore it was necessary to be done by reduction treatment at 1073 K-3.6 ks under hydrogen atmosphere. When sintering condition at 1673 K-3.6 ks was treated under vacuum condition, it gained the deflective strength of about 90%, and gained hardness and sintering density about same value compared with commercial alloys. As a result, it was able to recycle only by 7 processes, that is to say, tin impregnation, physical milling, stirring HCl cleaning, reduction, mixing, molding and sintering works.

Effect of GaAs surface treatments using HCl or (NH4)2Sx solutions on the interfacial bonding states induced by deposition of Au

The chemical bonding nature of the Au/GaAs interface has been investigated using monochromatic X-ray photoelectron spectroscopy (XPS), with an initially different GaAs surface obtained by HCl cleaning or S-passivation. The composition, chemical bonding state, and thickness of the interface were obviously dependent on the preparation of GaAs surface prior to Au-deposition. The interface region of Au/S-passivated GaAs was more uniform than Au/HCl-cleaned GaAs. In particular, surface bonding states such as AsO and AsS prior to Au-deposition were changed to GaO and GaS bonding due to the energy released from the deposition of Au, resulting in a combination of resultant As and Au. These bonding transitions were observed to occur at AsO/GaAs and AsS/GaAs interfaces. The bonding-layer distributions of the interfaces induced from non-destructive angle-resolved XPS measurements were Au/Au,AsO/AsAu/GaO/GaAs in the Au/HCl-cleaned GaAs, and Au/AsAu/AsS,GaS/GaAs in the Au/S-passivated GaAs.

XPS analysis of chemically etched II–VI semiconductor surfaces

X-ray photoelectron spectroscopy (XPS) was used to investigate the modification of the surfaces of ZnSe and ZnTe epitaxial films caused by HCl and NaOH cleaning. It was found that the HCl treatment successfully removed surface oxides but that the NaOH treatment did not. It was further found that the HCl treatment reduced the groupII/VI atomic ratios and promoted the formation of a group VI-rich surface.

Control of Etch Slope during Etching of Pt in Ar/Cl2/O2 Plasmas

Pt patterns of the 0.25 µ m design rule were etched at 20° C using a magnetically enhanced reactive ion etcher. The main problem of this device integration process is the redeposition of the etch products onto the pattern sidewall, making it difficult to reduce the pattern size. In both cases using a photoresist mask and an oxide mask, the redeposits of the etch products onto the sidewall were reduced by the addition of Cl2 to Ar, although the etch slope was lowered to 45°. Using the oxide mask, by adding O2 to the Cl-containing gas, the etch slope was increased up to 70°, and the redeposits were removed by an HCl cleaning process.