Copper grain growth in thin film Cu-Cr multilayers

Admon, U.; Dahan, Idit; Dariel, M.P.; Kimmel, G.; Sariel, J.; Shtechman, A.; Yahav, B.; Zevin, L.; Lashmore, D. S.

doi:10.1016/0040-6090(94)90673-4

Cited by 7 publications

(3 citation statements)

References 3 publications

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“…It is interesting to consider why Cu layers on the Cr were not effective in preventing the oxidation of Cr. While Cu and Cr do not form alloys, there are some indications that Cu and Cr do interact in a sufficiently strong manner that one can form materials with alternating Cu and Cr layers that are stable to at least 900 K. 24 Based on this, we anticipated that Cu would form a stable overlayer on the Cr and that the overlayer might prevent Cr oxidation. There are a number of possibilities for why this did not occur.…”

Section: Discussionmentioning

confidence: 99%

Enhanced Thermal Stability of Cu-Based SOFC Anodes by Electrodeposition of Cr

Gross

Vohs

Gorte

2006

J. Electrochem. Soc.

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The electrodeposition of Cr onto Cu-based, solid oxide fuel cell (SOFC) electrodes was investigated. Cu–ceria–YSZ (yttria-stabilized zirconia) electrodes were prepared by impregnation of porous YSZ with aqueous solutions of Cu(NnormalO3)2 and Ce(NnormalO3)3 and modified by the addition of a Cr layer onto the Cu. The addition of Cr had no effect on anode performance at 973K in humidified H2 but significantly improved the thermal stability. Without Cr, scanning electron microscopy showed structural changes in the Cu films after heating to 1173K , resulting in increased ohmic resistances in impedance spectra. The addition of Cr increased thermal stability so that the anodes were unaffected by heating to 1173K in dry H2 . Some oxidation of Cr was observed by X-ray diffraction following exposure of the composite to 80% normalH2–20% normalH2O mixtures at 973K for 20h , but partial oxidation of Cr did not affect the thermal stability of the anode. Exposure of the composite to 80% normalH2–20% normalH2O mixtures at 1173K for 20h resulted in complete oxidation of the Cr and a loss of enhanced thermal stability. Attempts to prevent Cr oxidation by the electrodeposition of Cu onto the Cr were unsuccessful. Based on these results, strategies for enhancing the stability of Cu-based anodes are discussed.

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Section: Discussionmentioning

confidence: 99%

Enhanced Thermal Stability of Cu-Based SOFC Anodes by Electrodeposition of Cr

Gross

Vohs

Gorte

2006

J. Electrochem. Soc.

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“…A normal grain growth is found for all Cu films, where the grain growth exponent n is ϳ2. 22,23 The relationship of ln͓͑D t 2 − D 0 2 ͒ / t͔ and 1 / T can be obtained from Eq. ͑7͒, as shown in Fig.…”

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confidence: 99%

Coupling effect of the electric and temperature fields on the growth of nanocrystalline copper films

Cao

Wang

et al. 2010

Phys. Rev. B

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The effect of an external static electric field on the grain growth in nanocrystalline Cu films was studied at different annealing temperatures. Transmission electron microscopy and x-ray diffraction indicate that the grain growth in Cu films is accelerated with various rates by an external electric field at different annealing temperatures. It is found that there is a coupling effect from the external electric and temperature fields on grain growth in Cu films during annealing. The growth rate is accelerated proportional to a factor f͑E͒ · T/100°C , which is determined from the theoretical derivation. The analysis indicates that the enhanced grain growth is achieved by the effect of the electric field on the vacancies migration and dislocation climb along grain boundaries.With the continuous down scaling of the size of integrated circuits ͑ICs͒, guaranteeing the reliability of microelectronic devices becomes a major challenge for semiconductor technology in the future. 1,2 Copper has a lower electrical resistivity and less electromigration than aluminum and has therefore become the dominant on-chip interconnect material in IC. 3,4 The use of copper enhances the working speed and reduces the interconnect resistance-capacitance delay. 5 The microstructure of Cu films, such as grain size and texture, can impact on the resistance to stress-induced migration and electromigration in Cu interconnects remarkably. 6,7 Generally, Cu lines with a bamboolike grain structure offer the significant advantage of antielectromigration and those with ͑100͒ texture have a higher resistance to stress-induced migration compared to those with ͑111͒ texture. 8 Especially in fast IC, the working temperatures can be quite elevated and similar holds for the electric fields that accompany small distances close to sharp features inside modern IC. 9,10 Moreover, special applications, as, for example, in certain sensors, often lead to high temperatures and high electric fields. These can change the microstructure of Cu lines 11 and will finally lead to the degeneration of the microelectronic devices. Thus, it is important to know how the microstructure of Cu films evolves in different conditions.It is well known that the growth of the grain size of nanoscale Cu films increases rapidly along with the annealing temperature. In addition to the temperature, it is also found that the electric field can influence the grain growth of metals. 12,13 However, it is still under debate whether external electric fields can accelerate grain growth or not. Jung and Conrad 14 found that the electric field could retard grain growth of electrodeposited Cu foil during annealing. However, Liu et al. 15 reported that the grain growth rate of Cu was accelerated by the field. Accelerated growth of the texture of cold-rolled steel under an applied electric field was also observed by He et al. 16 Consequently, the effect of the electric field on grain growth of Cu at different temperatures needs to be studied further. Especially interesting is the interdependence bet...

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“…In Cu-Cr multilayers with fcc͑111͒ structure no crystallization was observed in the Cr layers. 22 Furthermore, even though thick Cr films ͑ϳ30 ML͒ grown on fcc͑100͒ surface of Cu have body centered cubic ͑bcc͒ structure, a substantial distortion of the bcc structure was observed in the close vicinity ͑ϳ3 ML͒ of the Cu-Cr interface. 23 Therefore, using fcc monolayers for Cr on Cu surfaces is a reasonable approximation for both facets considered here.…”

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confidence: 99%

Magnetism-driven anomalous surface alloying between Cu and Cr

Kádas

Lindquist

Eriksson

et al. 2009

Applied Physics Letters

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Structure and magnetic properties of a two-dimensional c(2×2) Mn-Co/Cu(001) surface alloyCu-Cr contact materials are widely used as medium-and high-voltage vacuum interrupters. The microstructure of these materials is critical in their performance: the finer structure they have, the better are their physical properties. A solid solution of Cu and Cr could significantly increase the performance of such contact materials. However, Cu and Cr are practically immiscible in the bulk phase. Based on first principles density functional theory we show here that the solubility of Cr in Cu is dramatically increased on Cu surfaces already at room temperature and Cu-Cr alloys are formed on both the Cu͑111͒ and Cu͑100͒ surfaces. We demonstrate that the origin of this phenomenon is the unique magnetic properties of Cr atoms near surfaces.

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Copper grain growth in thin film Cu-Cr multilayers

Cited by 7 publications

References 3 publications

Enhanced Thermal Stability of Cu-Based SOFC Anodes by Electrodeposition of Cr

Enhanced Thermal Stability of Cu-Based SOFC Anodes by Electrodeposition of Cr

Coupling effect of the electric and temperature fields on the growth of nanocrystalline copper films

Magnetism-driven anomalous surface alloying between Cu and Cr

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