Papers by Keyword: Plasma Processing

Abstract: In relation to solid-rolled wagon wheels the advantages of differentiated quenching of all wheel elements are shown in comparison with quenching of only wheel rim rolling surface. It should be noted that larger possibilities to enhance performance characteristics of heavy duty details and products can be fulfilled using the technology of overall hardening including the differentiated quenching and surface plasma processing. It is established that along with the improvement of mechanical properties plasma processing after volume quenching allows for a considerable increase of crack resistance of surveyed grades in comparison with volume quenching without plasma processing. The martensite structure of the strengthened layer during such overall processing in comparison with the martensite structure of volume and strengthened base is characterized by high level of particle size that is specified by reduction of the original austenite grain due to very high heating and cooling speeds as well as small time of steel stay at high temperatures. In order to increase hardness and resistance against cracks generation plasma processing and preliminary volume quenching are recommended. A composite working layer with high wear and crack growth resistance and relatively soft and plastic core are developed in details and products volume quenched when surface plasma strengthening.

Abstract: The process of carbon dioxide reforming of hydrocarbon feedstock (like natural gas, coal, petroleum coke, residual oil, glycerine, etc) for hydrogen production has attracted great attention from both environmental and industrial perspectives. The plasma chemical reactor for study the CO₂ reforming of hydrocarbon gaseous feedstock is presented. The reactor consists of a DC plasma torch coupled to a compact quenching chamber. The linear plasma torch operates with a reverse vortex flow and hollow blind-end cathode for enhancing the thermal efficiency and enthalpy of the plasma jet. The quenching chamber consists of a set of refrigerated discs equipped with flow turbulent flow generator. Estimated quenching rates are up to 10⁷-10⁸ K/s. Electrical and thermal characteristics of the plasma-chemical reactor torch as well as the energy efficiency of the process are presented.

Abstract: The equipment for plasma processing with specific area of application – production of building materials – is proposed. For the proposed equipment the examination of possibilities is carried out. It was shown that plasma processing significantly affects the components of concrete – portland cement, fine filler (silica) and water. The treatment of portland cement leads to crystalline hydrate shell destruction and removal of chemically bound water. This, in turn, leads to the increase of strength by 15-20%. Plasma processing significantly changes the state of the fine filler. The total surface area of such a filler decreases due to flash-off effects. In Raman spectra all strong peaks of crystalline quartz disappear, and amorphization of quartz takes place after processing. If both cement and fine filler are processed than strength can be increased by 30%. By means of plasma processing of water it is possible not only to enlarge the strength of mortar, but also to increase the rate of curing. The improvement of properties is probably due to changes of hydration completeness in case of activated water.

Abstract: For the 45 nm interconnect technology node, porous dielectric materials (p-SiOCH) have been introduced, leading to complex integration issues due to their high sensitivity upon FC etching and ashing plasma exposure [1, 2]. Thanks to Metallic hard mask (MHM) integration high selectivities towards dielectric materials (>100:1) can be reached and minimizes exposure of p-SiOCH films to ashing plasmas. However MHM such as TiN generates other issues such as i) metal contamination in the patterned structures and ii) growth of metal based residues on the top of the hard mask [3, 4, 5]. The residues growth, which is air exposure time dependent, directly impacts the yield performance with the generation of via and line opens [.

Abstract: A layer of hardened material (crust) forms on the surface of photo resist (PR) during the implantation. This crust can be described as highly cross-linked polymer [1, 2]. Its thickness and composition depends on the type of PR, implant species, energy, dose, temperature during implantation and other factors. The crust is very resistant against chemical attack. Its chemical resistance tends to increase with the continuous shrink of technology nodes as implant doses increase. Moreover, even small residues of PR, left after cleaning, become more critical with shrinking device geometry. The usual process sequence for stripping a PR after high dose implantation (HDI) is a plasma strip (PS) followed by a wet clean. The drawback of plasma ashing is increased substrate loss and dopant bleach [3]. Plasma strip or plasma ash stand in this paper for the approach of complete PR consumption in the plasma process. Wet stripping alone often is not sufficient for stripping PR after implant doses of ≥ 1x1015 ions/cm2.

Abstract: A PADS (Plasma Assisted Debinding and Sintering) reactor developed by Lupatech S.A. has been employed to MIM process two Ni-based superalloys under Argon, at temperatures in the 1280 -1310 °C range, and for 2 to 3 hours. Both materials have chemical compositions similar to that of standard Nimonic® 90 but differ considerably in their powder characteristics. One type of powder was gas-atomized whereas the other was water-atomized. Samples of both materials in as-sintered states as well as subject to different HIP and heat treating conditions have been characterized mechanically in tensile tests and by HV measurements. The best overall results are attained by the water-atomized material sintered at lower temperatures. The PADS processing of these superalloys shows marked advantages over more conventional PM processing technologies. These results are particularly relevant to the development of turbine components for the automotive and aerospace industries.

Abstract: In this initial phase of work, two methods of backside wafer thinning using ICP plasma etching of two-inch SiC substrates have been considered. Plasma processes were optimized for nonbonded and bonded wafers. The non-bonded process was used to etch 250μm thick substrates to a final thickness of 100μm. The bonded process was used to etch glass bonded SiC substrates mechanically ground to 130μm thick and plasma etched to a final thickness of 100μm. Etch rate measurements and surface analysis were performed using a profilometer and white light interferometry. Etch rates of 3.4μm/min were achieved for the bonded process and 2.0μm/min for the non-bonded process. The surface morphology for the non-bonded process was three to four times lower than the bonded process. The part mechanically ground samples showed evidence of surface damage from the grinding process after plasma etching.

Abstract: Nitriding of metals and reactive spraying for nitride ceramics are planned using a 10-kW-class direct-current nitrogen or H2/N2-mixture arc plasma jet generator with a supersonic expansion nozzle in a low pressure environment. The H-atom electronic excitation temperature and the N2 molecule-rotational excitation temperature intensively decreased downstream in the nozzle although the NH molecule-rotational excitation temperature did not show an axial decrease. As approaching the titanium plate for nitriding, the thermodynamical nonequilibrium plasma came to be a temperature-equilibrium one. Both the electron number density near the plate and the heat flux into the plate increased with H2 mole fraction for mixtures gases. In cases with H2/N2-mixtures, a radical of NH with a radially wide distribution is considered to contribute to the better nitriding as a chemically active and non heating process. Numerical simulation was carried out to examine interactions between injected ceramic particles and the nitrogen plasma flow. When plasma was accelerated to supersonic flow through the nozzle, ceramic particles were smoothly accelerated by the aerodynamic drag force and heated in the highly-reactive plasma flow. The calculated results showed that the supersonic plasma jet in thermodynamical and chemical nonequilibrium state might have some potentials for material processing, even for spraying, because of its high reactivity.

Abstract: The influence of plasma processing of silica and crystalline silicon substrates on the formation of polymeric layers of PS/PMMA blends by sorption from 50 vol. % concentration toluene solutions was analyzed. The morphology dependence of PS/ PMMA blend films on the type and condition of substrate processing was studied by X-ray photoelectron spectroscopy (XPS), ellipsometry and atomic force microscopy (AFM). It was shown that reduction of carbon and oxygen components from the surface contaminants as well as the existence of a nonstoichiometric SiOx layer on the Si surface contributed to the hydrophilicity of the substrate. These processes can be used to produce thin nanostructured polymer blend films.

Abstract: Spectroscopic and electrostatic probe measurements were made to examine plasma characteristics under nitriding for a 10-kW-class direct-current arc plasma jet generator with a supersonic expansion nozzle in a low pressure environment. Heat fluxes into the plate from the plasma were also evaluated. Ammonia and mixtures of nitrogen and hydrogen were used as the working gas. The H-atom electronic excitation temperature and the N₂ molecule-rotational excitation temperature intensively decreased downstream in the nozzle although the NH molecule-rotational excitation temperature did not show an axial decrease. As approaching the titanium plate, the thermodynamical nonequilibrium plasma came to be a temperature-equilibrium one. Both the electron number density near the plate and the heat flux increased with H₂ mole fraction for mixtures gases. In cases with mixtures of N₂ and H₂, a radical of NH with a radially wide distribution is considered to contribute to the better nitriding as a chemically active and non heating process.