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In direct current plasma nitriding (DCPN), the treated components are subjected to a high cathodic potential, which brings several inherent shortcomings, e.g., damage by arcing and the edging effect. In active screen plasma nitriding (ASPN) processes, the cathodic potential is applied to a metal screen that surrounds the workload, and the component to be treated is placed in a floating potential. Such an electrical configuration allows plasma to be formed on the metal screen surface rather than on the component surface; thus, the shortcomings of the DCPN are eliminated. In this work, the nitrided experiments were performed using a plasma nitriding unit. Two groups of samples were placed on the table in the cathodic and the floating potential, corresponding to the DCPN and ASPN, respectively. The floating samples and table were surrounded by a steel screen. The DCPN and ASPN of the AISI 304 stainless steels are investigated as a function of the electric potential. The samples were characterized using scanning electron microscopy with energy-dispersive x-ray spectroscopy, x-ray diffraction, atomic force microscopy and transmission electron microscope. Dry sliding ball-on-disk wear tests were conducted on the untreated substrate, DCPN and ASPN samples. The results reveal that all nitrided samples successfully produced similar nitrogen-supersaturated S phase layers on their surfaces. This finding also shows the strong impact of the electric potential of the nitriding process on the morphology, chemical characteristics, hardness and tribological behavior of the DCPN and ASPN samples. [ABSTRACT FROM AUTHOR]

Nitriding treatments have been successfully applied to austenitic stainless steels to improve their hardness and tribological properties. However, at temperatures above 450 °C, conventional plasma nitriding processes decrease the corrosion resistance due to the formation of CrN phases within the modified layer. In this work, AISI 304 austenitic stainless steels were efficiently treated by rapid plasma nitriding at a high temperature of 530 °C in a hollow cathode discharge. The enhanced ionization obtained in the hollow cathode configuration provided a high current density and, consequently, a high temperature could be attained in a short time. The nitrided layers were characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The results indicated that the dual-layer structure of the nitrided layer consists of a high-N face-centered cubic structure with a free CrN precipitate outer (top) layer and a nitrogen-expanded austenite S-phase bottom layer. The rapid nitriding-assisted hollow cathode discharge technique permits the use of high temperatures, as high as 530 °C, without promoting degradation in the corrosion resistance of stainless steel. [ABSTRACT FROM AUTHOR]

This study investigates the microstructures and tribological behaviour in the modified layers of AISI 304 steel produced by active screen plasma oxynitriding. Compositional analysis of modified layers was carried out by field emission scanning electron microscopy, atomic force microscopy and high-resolution transmission electron microscopy. The results demonstrated that the modified composite duplex layer consisted of an amorphous and nanocrystalline oxynitrided layer (upper layer) and the nitrided layer (lower layer). Additionally, the wear resistance of the active screen plasma oxynitrided specimens was much higher than that of the untreated ones. The wear rate of the treated specimen decreased by approximately 95% compared with that of the untreated one. The analysis of the worn surface indicated that the treated specimen exhibited slight oxidation and abrasive wear, whereas the untreated one showed severe adhesive wear and plastic deformation. [ABSTRACT FROM AUTHOR]

AISI 420 martensitic stainless steel was treated by active screen plasma nitriding. The test table was placed inside the steel screen but isolated from the cathodic potential. The specimens, together with the furnace wall and test table, were earthed, resulting in formation of anodic potential. Treatments were carried out in NH 3 atmosphere of 400 Pa for 6 h at temperature ranging from 440 to 520 °C. The specimens were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and micro-hardness measurement. The results showed that anodic nitriding treatments were able to produce different types of modified surface layers at different temperatures. The thickness of the nitrided layers and surface roughness increased with the nitriding temperature. Dry sliding wear tests and electrochemical corrosion tests were conducted on the untreated substrate and nitrided specimens. It can be concluded that active screen plasma nitriding at anodic potential improved the hardness, wear resistance, and corrosion properties of AISI 420 stainless steel. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cobalt has been regarded as one of the most promising barrier metals for IC manufacturing. [•] The synergetic effect of H2O2 and glycine on the cobalt polishing performance is investigated. [•] The cobalt static etching rate and removal rate (RR) gradually decrease with increasing pH. [•] High concentration of H2O2 in slurry can suppress the cobalt RR. [ABSTRACT FROM AUTHOR]

Abstract: Ruthenium will be integrated into copper interconnects as a barrier layer in the near future. During the chemical mechanical polishing process of the ruthenium barrier layer, copper polishing performance with barrier slurries is crucial to microchips' final performance. This paper mainly studies the synergetic effect of benzotriazole (BTA) and non-ionic surfactant on copper polishing performance using KIO4-based barrier slurries. The results show that, the copper removal rate (RR) and static etching rate increase with increasing concentration of KIO4 due to the increasing proportion of the Cu–periodate and Cu–iodate compounds like Cu(IO4)2 and Cu(IO3)2 of the passivating film on the copper surface; the added BTA can further enhance the copper RR instead of suppressing it probably due to the formation of incomplete Cu–BTA thin film. It is demonstrated that the combination of BTA and non-ionic surfactant exhibits excellent performance in suppressing the copper RR to about 200Å/min, realizing satisfactory copper surface quality and achieving desirable material removal rate selectivity among copper, ruthenium and low-κ dielectrics. The synergetic passivation mechanism of BTA and non-ionic surfactant on the copper surface was investigated. It is proposed that in the presence of KIO4 as an oxidizer, the added BTA and non-ionic surfactant can form a porous passivating film on the copper surface which is mainly composed of the Cu–BTA complex, the adsorbed non-ionic surfactant and the leftover insoluble copper compounds like Cu(IO4)2 and Cu(IO3)2, and then the hydrophobic polypropylene oxide segments of non-ionic surfactant can be effectively absorbed on the hydrophobic Cu–BTA complex as a supplement. The above two parts are integrated into a complete passivating film to protect the copper surface from chemical dissolution and excessive mechanical abrasion. [Copyright &y& Elsevier]

In this paper, the kinematic analysis and numerical calculation are used to discuss the effect of the kinematic parameters on the final polishing result of typical rotary chemical-mechanical polishing (CMP) equipment. The relative velocity distribution and the sliding distance distribution are calculated based on the kinematic analysis. Especially, the coupling relationships between the kinematic parameters are investigated and discussed. And two parameters of the sliding distance nonuniformity (SDNU) and the sliding distance nonuniformity within concentric circles (SDNU\-cc) are proposed and calculated to evaluate the global uniformity of the sliding distance and to reveal the coupling relationships between the kinematic parameters. The results suggest that the relative velocity distribution and the sliding distance distribution are significantly affected by the coupling effects of the basic motions of CMP system; the SDNU is mainly affected by parameter \alpha, which represents the coupling relationship between the rotary motions of the wafer carrier and the polishing platen; the SDNU\-cc is mainly affected by parameter kT{0}^{\prime}(\alpha kT0), which represents the coupling relationship between the reciprocating motion and the rotary motion of the wafer carrier; \alpha\approx 1 and \alpha kT0>2 are proper for better polishing uniformity in real CMP process. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Trilon® P is used as a critical additive in copper slurries to improve the copper CMP performance, especially in the aspects of realizing low SER, low dishing and low dielectric erosion. [•] The chelating reactions between Trilon® P and cupric ions are revealed. [•] The reaction product Cu–Trilon® P complex has dual functions for copper CMP: passivation and lubrication vs. complexation and facilitation of (*OH) formation. [•] The adsorption of Trilon® P on the PETEOS surface can help form a lubricating thin film, and thus can result in low dielectric erosion. [ABSTRACT FROM AUTHOR]

Nanoparticles and two-dimensional (2D) nanosheets are well-investigated as lubricant additives, which can significantly reduce frictional energy consumption. However, the tribological properties of the additives will deteriorate because of the occurrence of aggregation in the lubricant and the difficulty in entering the frictional contact area. In the present work, the new sandwichlike nanostructure of Mn 3 O 4 nanoparticles and graphene nanosheets (Mn 3 O 4 @G) has been developed by an in situ green synthesis method; i.e., the impurities of Mn 2+ ions in crude graphite oxide as the precursor are directly transferred into Mn 3 O 4 precipitate between the graphene sheets. The graphene has a lamellar structure without folds and wrinkles, and the Mn 3 O 4 nanoparticles are not only uniformly anchored on the graphene surfaces but also intercalated in the layers of the graphene nanosheets. The Mn 3 O 4 @G exhibits excellent tribological properties and high stability because of a synergistic lubrication effect between the graphene nanosheets and the Mn 3 O 4 nanoparticles. Even at an ultralow concentration (0.075 wt %) and a high temperature of 125 °C, the friction coefficient and the wear depth have been reduced by 75% and 97% compared with base oil, respectively. The synthesis method and the Mn 3 O 4 @G nanocomposite have significant potential in various tribological applications for saving energy.

Two-dimensional (2D) nanocomposites as lubricant additives have been widely studied, but the synthetic process of the nanocomposites is not always environmentally friendly or economical. In this study, a new 2D nanocomposite, Fe 3 O 4 /h-BN, has been prepared by physical mixing of exfoliated h-BN nanosheets and organically modified Fe 3 O 4 nanoparticles. The nanocomposite displays a unique 2D-layered structure without folds or wrinkles. The Fe 3 O 4 nanoparticles are uniformly dispersed on the h-BN nanosheet surfaces with the help of an elegant self-assembly strategy from van der Waals interactions. For the first time, Fe 3 O 4 /h-BN is studied as a lubricant additive and it exhibits excellent tribological properties. The coefficient of friction (COF) and the wear depth can be respectively reduced by 47% and 80% compared with the base oil. Based on the advantages of a simple and low-cost synthetic process and significant tribological properties, Fe 3 O 4 /h-BN offers great potential for lubrication application., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)