Cu wetting and interfacial stability on clean and nitrided tungsten surfaces

Ekstrom, B.; Lee, Sungwon; Magtoto, N.P.; Kelber, Jeffry A.

doi:10.1016/s0169-4332(00)00816-3

Cited by 20 publications

(11 citation statements)

References 25 publications

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“…An additional factor preventing Cu-agglomeration on Ta could be due to a different interaction between Cu-Ta and Cu-Nitride since a similar behavior was reported for the Cu-W system [16].…”

Section: Discussionmentioning

confidence: 58%

Electrical properties of Ag/Ta and Ag/TaN thin-films

Mardani

Primetzhofer

Liljeholm

et al. 2014

Microelectronic Engineering

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a b s t r a c tAlthough wide band gap devices (WBG, e.g. GaN and SiC) are eminently suitable for high temperatures and harsh environments, these properties cannot be fully taken advantage of without an appropriate interconnect metallization. In this context, silver shows promise for interconnections at high temperatures. In this work, the thermal stability of Ag with two barrier metals -Ta and TaN -was therefore investigated. Metal stacks, consisting of 100 nm of silver on 45 nm of either Ta or TaN were sputterdeposited on the substrate. Each metal system was annealed in vacuum for one hour at temperatures up to 800°C. Both systems showed stable performance up to 600°C. The system with Ta as a barrier metal was found to be more stable than the TaN system. Above 700°C, silver agglomeration led to degradation of electrical performance.

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“…An additional factor preventing Cu-agglomeration on Ta could be due to a different interaction between Cu-Ta and Cu-Nitride since a similar behavior was reported for the Cu-W system [16].…”

Section: Discussionmentioning

confidence: 58%

Electrical properties of Ag/Ta and Ag/TaN thin-films

Mardani

Primetzhofer

Liljeholm

et al. 2014

Microelectronic Engineering

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“…For the thick Ta film, the uptake curve exhibits linear behavior with a change in slope at the 2 min deposition time, which indicates the conformal growth of Cu. 22 Cu/Ta XPS intensity error bars arising from the deviations from the average of the intensities are determined to be less than 5%. The surface thickness of Cu(d Cu ) present at the break in the uptake curve is estimated from Eq.…”

Section: Cu Growth Mode On Ta Film On Si-o-cmentioning

confidence: 89%

Ta metallization of Si–O–C substrate and Cu metallization of Ta/Si–O–C multilayer

Tong

Martini

Magtoto

et al. 2003

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Interfacial reactions of Ta with a Si–O–C low-dielectric constant (low-k) material and Cu/Ta/Si–O–C multilayers are investigated using x-ray photoelectron spectroscopy (XPS) and cross-sectional transmission electron microscopy (TEM). Data indicate that Ta deposition on the low-k substrate results in the initial formation of Ta oxide and TaC. Subsequent deposition of Ta eventually results in the formation of a metallic Ta overlayer at 300 K. The thickness of the initial Ta oxide/TaC-containing layer varies with the Ta deposition rate. At a deposition rate of ∼1 Å min−1, no metallic Ta is observed, even after 32 min sputter deposition time. In contrast, a film of roughly the same thickness, obtained after 15 s deposition at a rate of ∼2 Å s−1, is predominantly metallic Ta. Sputter deposition rates, derived from XPS data, are in agreement with film thicknesses derived from cross-sectional TEM data. Heating of Ta/low-k films in UHV results in no significant changes (as detected by XPS) up to 800 K. Cu deposited by sputter deposition onto a low-k surface covered with metallic Ta exhibits conformal growth, whereas 3d islanding is observed on a surface where TaC and Ta oxide are present. Cu diffusion into the bulk substrate is not observed at temperatures below 800 K in UHV.

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“…The presence of an interfacial oxide or hydroxide or sulfate region would suggest that factors governing Cu nucleation and growth during electrodeposition may differ fundamentally from those deduced in UHV surface science experiments. [2][3][4] In contrast, the absence of such an interfacial region at voltages positive to about Ϫ0.4 V indicates that kinetic factors ͑e.g., H-surface interactions or sulfate chemisorption͒ may be critical in controlling oxide/hydroxide formation, and therefore metal nucleation and adhesion.…”

Section: Discussionmentioning

confidence: 99%

“…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][3][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.…”

mentioning

confidence: 99%

Seedless Electrodeposition of Cu on Unmodified Tungsten

Wang

Lei

Rudenja

et al. 2002

Electrochem. Solid-State Lett.

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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...

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Cu wetting and interfacial stability on clean and nitrided tungsten surfaces

Cited by 20 publications

References 25 publications

Electrical properties of Ag/Ta and Ag/TaN thin-films

Electrical properties of Ag/Ta and Ag/TaN thin-films

Ta metallization of Si–O–C substrate and Cu metallization of Ta/Si–O–C multilayer

Seedless Electrodeposition of Cu on Unmodified Tungsten

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