Immersion/Electroless Deposition of Cu on Ta

Wang, Zuocheng; Li, Hongqi; Shodiev, Hasan; Suni, Ian Ivar

doi:10.1149/1.1667794

Cited by 11 publications

(15 citation statements)

References 16 publications

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“…Solution-based deposition techniques such as electrodeposition are attractive low-cost strategies to produce such ″ultrathin″ layers. Electroless deposition involves chemical instead of electrochemical reduction, and thus can be applied to substrates covered by electrically insulating oxide layers, enabling applications to base metals and interconnect diffusion barriers. , Galvanic displacement, a type of electroless deposition in which the substrate or an adsorbed species acts as the reducing agent, can produce nanometer-thickness films on semiconductors and noble metals. , Galvanic deposition of copper layers has been reported on oxide-covered materials such as aluminum, tantalum, as well as TiN and TaN diffusion barriers. − However, it seems that electroless deposition and galvanic deposition have not yet been used to fabricate ultrathin films on oxidized substrates.…”

Section: Introductionmentioning

confidence: 99%

Atom Probe Tomography Characterization of Thin Copper Layers on Aluminum Deposited by Galvanic Displacement

Zhang

Hillier

et al. 2012

Langmuir

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Abstract″Ultrathin″ metallization layers on the order of nanometers in thickness are increasingly used in semiconductor interconnects and other nanostructures. Aqueous deposition methods are attractive methods to produce such layers due to their low cost, but formation of ultrathin layers has proven challenging, particularly on oxide-coated substrates. This work focused on the formation of thin copper layers on aluminum, by galvanic displacement from alkaline aqueous solutions. Analysis by atom probe tomography (APT) showed that continuous copper films of approximately 1 nm thickness were formed, apparently the first demonstration of deposition of ultrathin metal layers on oxidized substrates from aqueous solutions. The APT reconstructions indicate that deposited copper replaced a portion of the surface oxide film on aluminum. The results are consistent with mechanisms in which surface hydride species on aluminum mediate deposition, either by directly reducing cupric ions or by inducing electronic conduction in the oxide, thus enabling cupric ion reduction by Al metal. Disciplines Chemical Engineering CommentsReprinted with permission from Langmuir 28 (2012) ABSTRACT: ″Ultrathin″ metallization layers on the order of nanometers in thickness are increasingly used in semiconductor interconnects and other nanostructures. Aqueous deposition methods are attractive methods to produce such layers due to their low cost, but formation of ultrathin layers has proven challenging, particularly on oxide-coated substrates. This work focused on the formation of thin copper layers on aluminum, by galvanic displacement from alkaline aqueous solutions. Analysis by atom probe tomography (APT) showed that continuous copper films of approximately 1 nm thickness were formed, apparently the first demonstration of deposition of ultrathin metal layers on oxidized substrates from aqueous solutions. The APT reconstructions indicate that deposited copper replaced a portion of the surface oxide film on aluminum. The results are consistent with mechanisms in which surface hydride species on aluminum mediate deposition, either by directly reducing cupric ions or by inducing electronic conduction in the oxide, thus enabling cupric ion reduction by Al metal.

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Section: Introductionmentioning

confidence: 99%

Atom Probe Tomography Characterization of Thin Copper Layers on Aluminum Deposited by Galvanic Displacement

Zhang

Hillier

et al. 2012

Langmuir

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“…5À7 Galvanic displacement, in which either the substrate itself or adsorbed atoms reduce the deposited metal ions, has been explored extensively for fabrication of metal films on semiconductors and noble metals, 8,9 and copper layers on barrier materials have been reported. 10,11 However, it seems that ultrathin films on oxidized substrates have not yet been fabricated by either ELD or galvanic displacement.…”

Section: ' Introductionmentioning

confidence: 99%

Copper Layers Deposited on Aluminum by Galvanic Displacement

Liu

Widharta

et al. 2011

J. Phys. Chem. C

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Metallization layers nanometers to tens of nanometers thick are desirable for semiconductor interconnects, among other technologically relevant nanostructures. Whereas aqueous deposition of such films is economically attractive, fabrication of continuous layers is particularly challenging on oxidized substrates used in many applications. Here it is demonstrated that galvanic displacement can deposit thin adherent copper layers on aluminum foils and thin films from alkaline copper sulfate baths. According to scanning electron microscopy and quartz crystal microbalance measurements, the use of relatively low CuSO4 concentrations produced films composed of copper nanoparticles overlying a uniform continuous copper layer on the order of nanometers in thickness. It seems that there are no precedents for such thin layers formed by aqueous deposition on oxidized metals. The thin copper layers are explained by a mechanism in which copper ions are reduced by surface aluminum hydride on Al during alkaline dissolution. Keywords Ames Laboratory Disciplines Chemical Engineering CommentsReprinted with permission from Journal of Physical Chemistry C 115 (2011) Because of their cost effectiveness, solution-based thin-film deposition techniques are widely integrated in semiconductor interconnect and MEMS technology. "Ultrathin" metallization layers of a few nanometers thickness are particularly beneficial in applications involving nanostructured substrates. In semiconductor interconnects, the ability to produce such deposits would eliminate the need for vapor-deposited seed layers for copper electrodeposition on TaN or TiN barrier materials. Efforts to produce seed layers by direct electrodeposition onto the barrier are hindered by the insulating, spontaneously formed oxide films on these materials. 1À4 Electroless deposition (ELD) methods, in which the deposited metal ion is chemically rather than electrochemically reduced, are attractive because they do not require conductive substrates. ELD of Cu on barrier materials has been demonstrated. 5À7 Galvanic displacement, in which either the substrate itself or adsorbed atoms reduce the deposited metal ions, has been explored extensively for fabrication of metal films on semiconductors and noble metals, 8,9 and copper layers on barrier materials have been reported. 10,11 However, it seems that ultrathin films on oxidized substrates have not yet been fabricated by either ELD or galvanic displacement.The present Article concerns the deposition of thin copper layers on aluminum by galvanic displacement. Aluminum exemplifies substrates having a surface oxide that interferes with solution-phase thin film deposition. Micron-thick particulate Cu films displaying good adhesion can be electrodeposited from alkaline sulfate baths; 12 also, several techniques have been developed to disrupt Al oxide layers to promote electrodeposition. 13À16Evidence of these papers suggests that deposition is promoted by alkaline solutions or by cathodic applied potentials at which hydrogen evolution...

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“…The electrodeposition and nucleation of copper from aqueous solutions on the naturally oxidized surface of tantalum is described by Emery et al, 9 Radisic et al 10 and Zheng et al 11 The nucleation of copper on tantalum, free of an intervening oxide film, is presented by Wang et al 12 In their study, this oxide layer is removed by galvanic displacement. To achieve a closed film an electroless step was needed and the presence of the interfacial suboxide TaO could not be excluded.…”

mentioning

confidence: 99%

Electrodeposition from a Liquid Cationic Cuprous Organic Complex for Seed Layer Deposition

Schaltin¹,

Brooks

Stappers³

et al. 2011

J. Electrochem. Soc.

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Continuous layers of 20 nm of copper have been deposited on a tantalum substrate from the liquid cationic cuprous organic complex [Cu(MeCN) 2 ][Tf 2 N]. This type of ionic liquid, with a high concentration of copper(I) ions permits to achieve high nucleation densities. Furthermore, extremely high overpotentials (up to 5.0 V) can be applied without decomposition of the ionic liquid. The deposition of copper has been investigated by cyclic voltammetry (CV), atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The resulting copper deposits can be useful as seed layers for aqueous copper filling.

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Immersion/Electroless Deposition of Cu on Ta

Cited by 11 publications

References 16 publications

Atom Probe Tomography Characterization of Thin Copper Layers on Aluminum Deposited by Galvanic Displacement

Atom Probe Tomography Characterization of Thin Copper Layers on Aluminum Deposited by Galvanic Displacement

Copper Layers Deposited on Aluminum by Galvanic Displacement

Electrodeposition from a Liquid Cationic Cuprous Organic Complex for Seed Layer Deposition

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