The utility of copper interconnects may ultimately depend on the ability to protect copper from corrosion. We have studied the capacity of lH-benzotriazole (1H-BTA) to provide a protective and stable surface film able to withstand harsh chemical and thermal environments. The film was characterized with electrochemical techniques, in situ ellipsometry, ex situ time-of-flight static secondary ion mass spectrometry, high-temperature mass spectrometry, and accelerated temperature and humidity tests. Several important passivating film properties (thickness, degree of polymerization, thermal stability, corrosion resistance) depend critically on the details of the film preparation conditions. The best corrosion protection is offered by the thin film formed on an oxidized Cu surface. This film has also shown the slowest growth kinetics and the highest degree of polymerization in the Cu-BTA structure.With more aggressive performance requirements for multilevel interconnections, higher conductivity metals, such as copper, are finding their way into a number of products. Copper is a relatively noble metal. Nevertheless, it reacts easily in ordinary, oxygen containing, environments (1). In view of the limited passivation offered by Cu-oxides, we have studied the effectiveness of organic azoles, such as lH-benzotriazole (1H-BTA), as a general method of controlling Cu degradation. For over 40 years 1H-BTA has been successfully used in the prevention of atmospheric Cu corrosion (2), in packaging, storage and transport, in the reduction of thermal oxidation and, in particular, in the protection of copper under immersed conditions (Ref. (3) and references within). The relevant literature is abundant but not unified in its teaching about bonding, thickness, composition and structure of the resulting film and the nature of its protection.Recent work from our laboratory, based on a combination of electrochemical, ellipsometric, and XPS data, has shown that the spontaneous reaction of Cu and 1H-BTA under a variety of conditions leads to the formation of Cu-BTA (4, 5), with copper being Cu +1 , as reported elsewhere (6-12). The formation of a Cu-N bond was clearly identified from the Cu LMM Auger lines. The film was formed both on an oxidized and an oxide-free Cu surface, in contrast to reports suggesting that the presence of Cu 2 O is a prerequisite for the buildup of 14). The thickness of the film was determined to be 0.5-4 nm in the pH range from 3 to 12, reaching 25 nm only under harsh conditions, i.e., in pH 2. Several recent studies of ultrahigh vacuum deposited 1H-BTA have indeed detected 1H-BTA adsorption on clean Cu metal (14-16). An electrochemical equivalent of such a film was formed in our laboratory at Cu 0 kept in
Articles you may be interested inThioethanol on Cu(111) at room temperature: A near edge x-ray absorption fine structure and x-ray photoelectron spectroscopy study J. Vac. Sci. Technol. A 22, 683 (2004); 10.1116/1.1724837 X-ray photoelectron spectroscopy characterization of the oxidation of electroplated and sputter deposited copper surfaces J.
Nuclear magnetic resonance ͑NMR͒ spectroscopy has been used in conjunction with voltammetry to investigate the mechanism for the electrocatalytic oxidation of CO on a carbon-supported Pt fuel cell electrocatalyst in 2 M H 2 SO 4 at ambient temperature. The states of adsorbed CO͑CO ads ͒, the conditions which give rise to them, and their oxidation pathways were investigated as a function of CO ads coverage and the working electrode potential of adsorption (E ads ). CO was adsorbed from the electrolyte at various fixed values of E ads between 0 and 600 mV vs. RHE. Submonolayer coverages of CO ads were formed in two different ways, by adsorption for limited amounts of time and by partial oxidation of an initially saturated coverage. The CO ads coverage was then characterized via voltammetric oxidation and via 13 C NMR. Voltammetry data were analyzed qualitatively in terms of the number, shape, and position of CO ads oxidation peaks and quantitatively in terms of the total charge required to oxidize the CO ads coverage and the total number of catalyst sites occupied by the CO ads . NMR spectra were analyzed qualitatively in terms of their lineshape and position and quantitatively in terms of their integrated intensity. These results have been utilized in the formulation of an overall model for the adsorption and oxidation of CO on Pt in an acid electrolyte at ambient temperature. Three distinct forms of CO ads are identified on the Pt electrocatalyst, a linear carbonyl, a bridged carbonyl, and a reduced carbonyl ͑a hydrogenated carbonyl requiring a three-electron transfer for complete oxidation to CO 2 ͒. The relative populations of these three species are found to depend strongly on E ads and to be substantially independent of coverage. Different oxidation behaviors are observed for different populations of the three CO ads species, suggesting that different oxidation reaction pathways are associated with the three CO ads states.
It has been demonstrated that high quality single-crystal Cu-Ni mutlilayers may be grown electrochemically provided appropriate attention is given to substrate preparation and the structural consequence of the electrocrystallization reactions. These films should be useful for developing a clearer understanding of the relationship between the modulation wavelength, orientation, and the physical properties of multilayered materials. ABSTRACTPotentiostatic current oscillations observed during the anodie dissolution of an iron electrode in a sulfuric acid electrolyte are considered. This behavior has been experimentally characterized with respect to its potential dependence. A new mechanism has been developed that is consistent with observed behaviors and trends. This mechanism combines previously developed ideas concerning periodic behavior and passivation of iron with a new interpretation of precipitated salt-film behavior. The salt film is taken to be nonporous, serving as both a necessary precursor to oxide passivation as well as an effective passivating species itself. The mechanism is well corroborated by results from a mathematical model which also highlights the necessity of salt-film precipitation for the development of periodic behavior. Additionally, the issue of coherence is explicitly considered. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.126.162.126 Downloaded on 2015-03-13 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.126.162.126 Downloaded on 2015-03-13 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.126.162.126 Downloaded on 2015-03-13 to IP
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