X-ray photoelectron spectroscopy (XPS), low energy electron diffraction, and cyclic voltammetry have been used to study the adsorption of iodine on the Ru(0001), air, and water exposure to both clean and iodine covered Ru(0001) surfaces and the stability of the iodine adlayer during Cu overpotential electrodeposition. A normalRufalse(0001false)­false(3×3false)R30°­I structure was observed after I2 vapor exposure of the Ru(0001) surface at room temperature. The normalRufalse(0001false)­false(3×3false)R30°­I structure was found to be stable toward ambient air and water exposure. The I ad-layer passivates the Ru(0001) surface against significant hydroxide, chemisorbed oxygen, or oxide formation during exposure to air. Immersion of I-Ru(0001) results in greater hydroxide and chemisorbed oxygen formation than air exposure. A saturation coverage of I on a Ru(poly) electrode similarly passivated the Ru surface against oxidation upon exposure to water vapor over an electrochemical cell in an ultrahigh vacuum electrochemistry transfer system. Studies with combined electrochemical and XPS techniques show that iodine surface adlayer remained on top of the surface after cycles of overpotential electrodeposition/dissolution of copper on Ru(0001). These results indicate the potential bifunctionality of the iodine layer to both passivate the Ru surface in the microelectronic processing and to act as a surfactant for copper electrodeposition. © 2004 The Electrochemical Society. All rights reserved.

No abstract

Adherent Cu films were electrodeposited on polycrystalline W foils from a purged 0.05 M CuSO 4 solution in H 2 SO 4 supporting electrolyte at pH 1. Films were deposited under constant potential conditions at voltages between Ϫ0.6 and Ϫ0.2 V vs. Ag/AgCl. The films produced by pulses of 10 s duration were visible to the eye, copper colored, and survived the Scotch tape test. Characterization by scanning electron microscopy and X-ray photoelectron spectroscopy ͑XPS͒ confirmed the presence of Cu, with apparent dendritic growth. No sulfur impurity was observable by XPS. Kinetics measurements indicated that the Cu nucleation process is slow compared to recently reported kinetics for Cu electrodeposition on TiN. The adhesion of the deposited Cu strongly suggests the absence of an interfacial oxide.The electrodeposition of Cu onto barrier surfaces is of considerable importance in the development of Cu interconnect processes for deep submicrometer devices. Current processing usually involves electrodeposition from a sulfate bath onto a Cu seed layer, which is first deposited by plasma vapor deposition ͑PVD͒ or metallorganic chemical vapor deposition ͑MOCVD͒. Conformal, uniform seed layer deposition becomes increasing problematic as device dimensions continue to shrink; 1 electrodeposition in the absence of a seed layer is desirable. Surface science studies carried out in ultrahigh vacuum ͑UHV͒, however, indicate that the ability of Cu adlayers to wet ͑grow conformally on͒ a Ta or W barrier surface is severely degraded by the presence of even monolayer coverages of oxygen. 2-4 The electrodeposition of Cu onto reactive metal surfaces in aqueous environments therefore presents obvious difficulties. Under acidic conditions ͑pH ϳ1 or lower͒, and cathodic potentials, W metal is predicted 5 to be thermodynamically stable relative to its oxides. Exploratory studies of Cu electrodeposition on W in the absence of a Cu seed layer were therefore carried out under these conditions. ExperimentalStudies were carried out in a flat three-electrode cell fitted with a Luggin capillary and a platinum-rhodium counter electrode. All potentials reported here are referenced to Ag/AgCl. The cell was configured so that the area of the electrode accessible by the electrolyte was 1 cm 2 . The solutions used for these studies consisted of 0.05 M CuSO 4 in H 2 SO 4 at pH 1.0. Solutions were purged with N 2 for Ͼ1.5 h prior to each experiment. Polycrystalline W foils ͑Ͼ99.95% pure͒ were used as working electrodes. Foils were rinsed in acetone, ethanol, and distilled water prior to use. Electrochemical measurements were carried out using a commercially available potentiostat ͑EG&G 263A͒ and software. Scanning electron microscopy ͑SEM͒ data were acquired using a JEOL 300S model with an energy dispersive analysis by X-ray ͑EDAX͒ attachment for elemental analysis. X-ray photoelectron spectroscopy ͑XPS͒ data were acquired with a hemispherical analyzer operated in constant pass energy mode ͑50 eV͒ and unmonochromatized Mg K␣ radiation. Results and Discussion...

No abstract