The crystal structure of η-Cu<sub>3</sub>Si precipitates in silicon

Solberg, Jan Ketil

doi:10.1107/s0567739478001448

Cited by 196 publications

(81 citation statements)

References 10 publications

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“…It is known that Cu reacts with Si to form Cu 3 Si intermetallic compound 2,36 at the interface, rendering a complicated Cu/Si interfacial structure unattainable by first-principles calculations. Here, we focus on unreconstructed Cu/Si interfaces instead with two orientations: Cu ͑111͒/Si ͑111͒ ͑Refs.…”

Section: Cu/si Interfacementioning

confidence: 99%

First-principles simulations of copper diffusion in tantalum and tantalum nitride

Zhao

Lü

2009

Phys. Rev. B

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To explore potential applications of tantalum and tantalum nitrides ͑TaN͒ as diffusion barrier materials in integrated circuits with Cu interconnects, we carry out detailed first-principles simulations of Cu/Ta and Cu/TaN systems. Various interfacial structures between Cu-and Ta-based compounds are examined by considering different surface orientations, in-plane arrangements, surface terminations, and chemical compositions. The coexistence of strong Cu-N ionic bonding and Ta-Cu covalent/metallic bonding dictates the stable interfacial structures. Using nudged elastic band method, we calculate the diffusion energy barriers of Cu to the pre-existing vacancies across Cu/Ta, Cu/TaN interfaces, and in bulk TaN compounds. As a comparison, Cu diffusion in Si is also studied. It was found that Cu can easily diffuse into Si either spontaneously or with small energy barriers. On the other hand, although the Cu/Ta interfacial diffusion barrier is low, the high vacancy formation energy in Ta renders Cu diffusion difficult. We find that fcc TaN is an excellent candidate for diffusion barrier material owing to its extremely high interfacial diffusion energy barrier. The bulk diffusion barrier of Cu in fcc TaN is also very high.

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Section: Cu/si Interfacementioning

confidence: 99%

First-principles simulations of copper diffusion in tantalum and tantalum nitride

Zhao

Lü

2009

Phys. Rev. B

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“…For multicrystalline silicon (mc-Si), material out of which over 50% of solar cells worldwide are made, metal precipitation reactions are further complicated by the inhomogeneous presence of structural defects and the possible presence of up to 15 metallic impurity species in concentrations as high as 10 12 cm À3 or greater [3][4][5]. It is also commonly accepted as well that interstitially dissolved 3d transition metals in silicon (e.g., iron or copper) can, upon supersaturation, precipitate into their solid equilibrium metal silicide phase (e.g., FeSi 2 [6] or Cu 3 Si [7][8][9]). It is also fairly well established that the presence of precipitates of one metal species may aid the precipitation of another (see [10] and references therein), e.g., by providing energetically favorable nucleation sites via lattice strain or local native point defect compensation.…”

Section: Introductionmentioning

confidence: 99%

Transition metal co-precipitation mechanisms in silicon

et al. 2007

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“…27 Previous studies that have attempted to determine the chemical state of Cu-rich clusters in Si are largely restricted to TEM-based energy dispersive x-ray spectroscopy (EDX) and diffraction analyses of copper precipitates in samples prepared by in-diffusion of unusually high Cu concentrations, or grown from a heavily Cu-contaminated melt. [28][29][30][31][32][33] In these studies, a species of copper silicide, η-Cu 3 Si, is the predominantly observed phase.…”

Section: Introductionmentioning

confidence: 99%

Analysis of copper-rich precipitates in silicon: Chemical state, gettering, and impact on multicrystalline silicon solar cell material

Buonassisi

Marcus

Istratov

et al. 2005

Journal of Applied Physics

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In this study, synchrotron-based x-ray absorption microspectroscopy (µ-XAS) is applied to identifying the chemical states of copper-rich clusters within a variety of silicon materials, including as-grown cast multicrystalline silicon solar cell material with high oxygen concentration and other silicon materials with varying degrees of oxygen concentration and copper contamination pathways. In all samples, copper silicide (Cu 3 Si) is the only phase of copper identified. It is noted from thermodynamic considerations that unlike certain metal species, copper tends to form a silicide and not an oxidized compound because of the strong silicon-oxygen bonding energy; consequently the likelihood of encountering an oxidized copper particle in silicon is small, in agreement with experimental data. In light of these results, the effectiveness of aluminum gettering for the removal of copper from bulk silicon is quantified via x-ray fluorescence microscopy (µ-XRF), and a segregation coefficient is determined from experimental data to be at least (1-2)×10 3 . Additionally, µ-XAS data directly demonstrates that the segregation mechanism of Cu in Al is the higher solubility of Cu in the liquid phase. In light of these results, possible limitations for the complete removal of Cu from bulk mcSi are discussed.

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The crystal structure of η-Cu₃Si precipitates in silicon

Cited by 196 publications

References 10 publications

First-principles simulations of copper diffusion in tantalum and tantalum nitride

First-principles simulations of copper diffusion in tantalum and tantalum nitride

Transition metal co-precipitation mechanisms in silicon

Analysis of copper-rich precipitates in silicon: Chemical state, gettering, and impact on multicrystalline silicon solar cell material

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The crystal structure of η-Cu3Si precipitates in silicon

Cited by 196 publications

References 10 publications

First-principles simulations of copper diffusion in tantalum and tantalum nitride

First-principles simulations of copper diffusion in tantalum and tantalum nitride

Transition metal co-precipitation mechanisms in silicon

Analysis of copper-rich precipitates in silicon: Chemical state, gettering, and impact on multicrystalline silicon solar cell material

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The crystal structure of η-Cu₃Si precipitates in silicon