Pre-cleaning Step Research Articles

Serum protein profiling using surfactant-aided matrix-assisted laser desorption/ionization mass spectrometry

It has been shown previously that sodium dodecyl sulfate (SDS) can be used at its critical micellar concentration to increase the number of peptides detected in a peptide mixture by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Here we demonstrate that, in a similar fashion, preparation of peptides and low molecular weight proteins from serum using SDS micelles improves the information content in MALDI-MS. In particular, the addition of SDS yielded a 30% increase in the number and a 50% increase in the abundance of low molecular weight (<6000 Da) analytes. C 18 ziptips and C 18 magnetic beads were used as pre-cleaning steps for comparative analysis and it was found that magnetic beads were more suitable for pre-cleaning prior to combining the eluent with SDS. The non-ionic surfactant n-octyl-β- d-glucopyrinoside yielded improved ion abundances of peptides with masses above 6000 Da, although these increases are less dramatic than those found with SDS. These results demonstrate that surfactant-aided MALDI-MS can lead to an increase in the amount of information obtained from complex mixtures of peptides/proteins. Such improvements may prove advantageous for applications such as those focused on protein profiling.

Study on the transmission of deoxynivalenol and de-epoxy-deoxynivalenol into eggs of laying hens using a high-performance liquid chromatography-ultraviolet method with clean-up by immunoaffinity columns

The transmission of deoxynivalenol (DON) and of its metabolite de-epoxy-DON into eggs has not been sufficiently elucidated until now. This question was addressed within the scope of a 16-week experiment with laying hens which were fed a maize-based diet with a DON concentration of 11.9 mg x kg(-1 )dry matter. Eggs were collected during weeks 2, 4, 8, and 16 of the experiment, and DON and its metabolite de-epoxy-DON were analyzed in freeze-dried yolk and albumen. In order to cover possible conjugates, all samples were incubated with beta-glucuronidase prior to extraction. Yolk and albumen were extracted with acetonitrile-water, and the extracts were purified with immunoaffinity columns (IACs) after a precleaning step. The toxins were determined by high-performance liquid chromatography (HPLC) with UV detection. The detection limits of both toxins were 5 and 8 microg x kg(-1) in freeze-dried yolk and albumen, respectively, corresponding to approximately 2.5 and 1 microg x kg(-1) in fresh samples. The recovery of DON and de-epoxy-DON in yolk was 80% and 78%, respectively, and in albumen 77 and 72%. Neither DON nor de-epoxy-DON or glucuronide conjugates of both substances could be detected in any of the samples. These results indicate that eggs do not contribute significantly to the dietary DON intake of humans.

Copper interconnect electromigration behaviors in various structures and lifetime improvement by cap/dielectric interface treatment

Copper interconnect electromigration performance was examined in various structures and three low- k materials ( k = 2.65–3.6) using advanced BEOL technology. Strong current dependence effect on electromigration lifetime in three levels via terminated metal lines structure was shown. Moreover, different process approach will lead to different EM behavior and related failure mode. Multi-modality electromigration behavior of Cu dual damascene interconnects were studied. Both Superposition and Weak-Link models were used for statistical determination of lifetimes of each failure models (Statistical method). Results were correlated to the lifetimes of respective failure models physically identified according to resistance time evolution behaviors (Physical method). Good agreement was achieved. Various testing structures are designed to identify the EM failure modes. Extensive failure analysis was carried out to understand the failure phenomena of various test structures. The activation energies of failure modes were calculated. The weak links of interconnect system were also identified. A significant improvement of electromigration (EM) lifetime is achieved by modification of the pre-clean step before cap-layer deposition and by changing Cu cap/dielectric materials. A possible mechanism for EM lifetime enhancement was proposed. Cu-silicide formation before cap-layer deposition and adhesion of Cu/cap interface were found to be critical factors in controlling Cu electromigration reliability. The adhesion of the Cu/cap interface can be directly correlated to electromigration MTF and activation energy. Results of present study suggest that interface of Cu interconnects is the key factor for EM performance for advanced BEOL technology design rules.

Prevention method of a notching caused by surface charging in silicon reactive ion etching

This paper proposes a method to prevent silicon from a notching in a reactive ion etching (RIE) process by introducing a self-aligned metal interlayer to a silicon/glass bonded fixture. A metal interlayer prevents a charge buildup at the bottom of a silicon trench, therefore silicon structures do not suffer from charge-induced local damage. A self-aligning process of Ti/Au interlayer is accomplished by a lift-off process using a photoresist etch mask as a sacrificial layer. Titanium is a diffusion barrier of gold to silicon and gold is preferred due to its chemical stability in a pre-cleaning step. The effectiveness of the proposed method is verified by applying it to the fabrication of a simple trench and comb electrode. The applicability of the proposed methodology is examined by fabricating an optical knife edge device.

Determination of 4-amino- m-cresol and 5-amino- o-cresol and metabolites in human keratinocytes (HaCaT) by high-performance liquid chromatography with DAD and MS detection

A multi-step gradient HPLC system combined with DAD and MS detection has been developed for the determination of the oxidation hair dyes 4-amino- m-cresol (4-AC) and 5-amino- o-cresol (5-AC) and their metabolites in the alternative testing system human keratinocytes (HaCaT) cell culture. The culture medium induced by 3-methylcholanthrene (3-MC) was fortified with 4-AC or 5-AC and incubated for 24 h at 37 °C in order to produce metabolites. After several pre-cleaning steps, further cleaning was done by solid-phase extraction using C18 phenyl cartridges. Optimizing chromatographic conditions, a hybrid-based RP8 column was most suitable for the separation of the metabolites formed in HaCaT. Only one conjugation product, the N-acetylated derivative, could be identified for both 4-AC and 5-AC by LC/DAD/MS. The ionisation technique used for MS analysis was Atmospheric Pressure Ionization (API).

The Effects of Residual RTOs on Formation of CoSi2 and Its Properties for 0.18 μm CMOS

The effects of residual oxides formed on polycrystalline Si and active Si on the formation of and its sheet resistance for 0.18 μm complementary metal oxide semiconductors (CMOS) have been investigated considering its formation regions and process parameters such as polycrystalline structure and grain size, kinds of dopant, and integration schemes. Having a columnar-type polycrystalline Si, strong linewidth dependence of the sheet resistance was observed in the p+ polycrystalline regions but not in the n+ polycrystalline regions or the n+/p+ diffusion regions. The same results were also observed when a granular-type polycrystalline Si was deposited as a gate material. The sheet resistance of in the p+ polycrystalline regions having a granular-type polycrystalline Si is higher than that of a columnar-type polycrystalline Si at all gate lengths. These results were found to be due to oxide that resided on the surface of polycrystalline Si in the p+ polycrystalline regions and due to the larger area of grain boundary. An alternative integration has no linewidth dependence in any silicided regions down to 0.15 μm gate length through removing the rapid thermal oxide (RTO) completely, which was used to block the dopants’ out-diffusion from the source/drain and gate during the source/drain annealing that was processed before the cobalt deposition. Confirmation of these results was processed through lengthening the time of the diluted HF precleaning step to remove the RTO completely. © 2004 The Electrochemical Society. All rights reserved.

Nutrient removal efficiency and resource economics of vertical flow and horizontal flow constructed wetlands

In order to reduce the very high costs of sewage disposal in the new federal states of Germany, more decentralized purification systems need to be established. To attain higher surface water quality, and thereby the acceptance of such systems by governmental authorities, good removal rates for organic substances and also for nutrients (N, P) are necessary. Constructed wetlands for wastewater treatment (reed-bed systems) in Germany and in the USA have been used successfully. This study compares the purification performances of constructed horizontal flow wetlands (HFW) and vertical flow wetlands (VFW), including: (1) a small horizontal flow wetland (HFW); (2) a sloped HFW; (3) a larger HFW; (4) a stratified vertical flow wetland (VFW); and (5) an unstratified VFW. It is shown that both the horizontal flow and vertical flow systems can remove more than 90% of organic load and of total N and P, if there is an effective precleaning step, and if the specific treatment area is great enough (>50 m 2/m 3 per d). HFWs have an advantage in long-term removal of P because it is bound to organic substances to a high degree. Decentral and semicentral natural treatment systems also save material (76%) and energy (83%) for their function compared with central technical systems.

Oxide degradation during selective epitaxial growth of silicon

A derivative of selective epitaxial growth and epitaxial lateral overgrowth, has been devised to create single-crystal silicon on insulator structures. The effect of conditions present in selective epitaxial growth and epitaxial lateral overgrowth on the electrical characteristics of the insulating masking oxides has been studied. It was determined that thin (&amp;lt;150 nm) oxides were attacked by the ambient employed in selective epitaxy. The rate of degradation increased with decreasing oxide thickness and with the addition of silicon-containing species to the gas phase. The observed defect formation may be related to the oxide decomposition during annealing in oxygen-free ambients and the undercutting of masking oxide at the Si-SiO2 interface during the in situ preclean step used in epitaxial processes.

Relationship between beam and junction parameters in ion beam processed Josephson devices

Planar and edge-defined niobium-lead alloy Josephson junctions were fabricated using an ion beam tunnel barrier process consisting of Ar cleaning and Ar/O2 oxidation, with ion energies as low as 50 eV in the oxidation step, during which the ion energy and flux, oxygen fraction, and process time control junction critical current density. The effect of these process parameters on junction properties was studied using a 30-mm ion source and 57-mm wafers. Both run-run and on-wafer spatial variations were measured. Comparison of ion flux profiles with distributions of junction critical current densities revealed that the Ar preclean step, as well as the oxidation step, is important in controlling process uniformity. The results indicate that uniformity adequate for large scale integrated circuit applications should be attainable.

Substrate Cleaning for Integrated Optical Waveguides

Losses in integrated optical waveguides depend upon the homogeneity of the guiding layer. Successful production of acceptable guides by sputtering or solution deposition depends critically on the methods used to clean the substrate. Cleaning methods that produce films adequate for ordinary coatings have proved inadequate for integrated optical films. The extreme cleanliness required to produce low-loss waveguides can be achieved by a process described in this paper, which utilizes a precleaning step in an ultrasonically agitated detergent bath followed by careful rinsing in an ultrasonically agitated bath of heated, deionized, and filtered water. In addition to the cleaning method, we discuss the design of a cleaning station that combines the necessary apparatus in a portable unit.