The evolution of diffusion barriers in copper metallization

Lee, Chiapyng; Kuo, Yu‐Lin

doi:10.1007/s11837-007-0009-4

Cited by 67 publications

(60 citation statements)

References 17 publications

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“…In comparison, diffusion coefficients published for polycrystalline TiN barrier layers are typically in the range of 10 -15 -10 -14 cm 2 s -1 for annealing temperatures of 900 °C and would be even higher at 1000 °C [4,31]. This illustrates the strong influence of grain boundaries on the performance of the diffusion barrier.…”

Section: Experimental Findingsmentioning

confidence: 96%

Copper diffusion into single-crystalline TiN studied by transmission electron microscopy and atom probe tomography

Mühlbacher¹,

Martín²,

Sartory³

et al. 2015

Thin Solid Films

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Section: Experimental Findingsmentioning

confidence: 96%

Copper diffusion into single-crystalline TiN studied by transmission electron microscopy and atom probe tomography

Mühlbacher¹,

Martín²,

Sartory³

et al. 2015

Thin Solid Films

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“… The barrier material should be a good electrical and thermal conductor. A milestone in IC design was the replacement of the conventional Al (metallization)/SiO 2 (dielectric) technology with Cu metallizations in combination with low-k (where k stands for the dielectric constant) materials [4,92,93]. By reducing both the resistivity of and capacitance between the interconnects, signal delay times are lowered significantly [3,92].…”

Section: Barrier Requirementsmentioning

confidence: 99%

“…Especially Cu and Si are very reactive even at temperatures as low as 200 °C, and the insertion of a barrier layer between the metallization and the surrounding materials as illustrated in Fig. 9 is paramount to ensure functionality of the device [4]. Thus, with the advent of ULSI, IC dimensions on the nm-scale and the replacement of Al metallization by Cu, additional requirements placed upon diffusion barriers have emerged [4,89]:  The barrier should be less than 5 nm thick (for high-resistivity barriers), or should have an electrical conductivity similar to Cu.…”

Section: Barrier Requirementsmentioning

confidence: 99%

“…9 is paramount to ensure functionality of the device [4]. Thus, with the advent of ULSI, IC dimensions on the nm-scale and the replacement of Al metallization by Cu, additional requirements placed upon diffusion barriers have emerged [4,89]:  The barrier should be less than 5 nm thick (for high-resistivity barriers), or should have an electrical conductivity similar to Cu.  The material must meet advanced processing demands (including uniform deposition of trench walls and bottoms and anisotropic dry-etching).…”

Section: Barrier Requirementsmentioning

confidence: 99%

“…In particular, diffusion barriers that separate the adjacent materials (mostly dielectrics and semiconductors) from the metal interconnect (where Cu has replaced Al) in microelectronics play a critical role and are often decisive for device performance and lifetime [3]. They prohibit the migration of atoms from the Cu metallization to the surrounding dielectrics or the Si substrate and vice versa, so that no chemical reactions potentially impairing the device functionality can occur [4]. Due to its favorable structural, thermal and electronic properties, TiN is a stateof-the-art diffusion barrier material.…”

Section: Introductionmentioning

confidence: 99%

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High-resolution characterization of TiN diffusion barrier layers

Mühlbacher¹

2015

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Titanium nitride (TiN) films are widely applied as diffusion barrier layers in microelectronic devices. The continued miniaturization of such devices not only poses new challenges to material systems design, but also puts high demands on characterization techniques. To gain understanding of diffusion processes that can eventually lead to failure of the barrier layer and thus of the whole device, it is essential to develop routines to chemically and structurally investigate these layers down to the atomic scale. In the present study, model TiN diffusion barriers with a Cu overlayer acting as the diffusion source were grown by reactive magnetron sputtering on MgO(001) and thermally oxidized Si(001) substrates. Cross-sectional transmission electron microscopy (XTEM) of the pristine samples revealed epitaxial, single-crystalline growth of TiN on MgO(001), while the polycrystalline TiN grown on Si(001) exhibited a [001]-oriented columnar microstructure. Various annealing treatments were carried out to induce diffusion of Cu into the TiN layer. Subsequently, XTEM images were recorded with a high-angle annular dark field detector, which provides strong elemental contrast, to illuminate the correlation between the structure and the barrier efficiency of the single- and polycrystalline TiN layers. Particular regions of interest were investigated more closely by energy dispersive X-ray (EDX) mapping. These investigations are completed by atom probe tomography (APT) studies, which provide a three-dimensional insight into the elemental distribution at the near-interface region with atomic chemical resolution and high sensitivity. In case of the single-crystalline barrier, a uniform Cu-enriched diffusion layer of 12 nm could be detected at the interface after an annealing treatment at 1000 °C for 12 h. This excellent barrier performance can be attributed to the lack of fast diffusion paths such as grain boundaries. Moreover, density-functional theory calculations predict a stoichiometry-dependent atomic diffusion mechanism of Cu in bulk TiN, with Cu diffusing on the N-sublattice for the experimental N/Ti ratio. In comparison, the polycrystalline TiN layers exhibited grain boundaries reaching from the Cu-TiN interface to the substrate, thus providing direct diffusion paths for Cu. However, the microstructure of these columnar layers was still dense without open porosity or voids, so that the onset of grain boundary diffusion could only be found after annealing at 900 °C for 1 h. The present study shows how to combine two high resolution state-of-the-art methods, TEM and APT, to characterize model TiN diffusion barriers. It is shown how to correlate the microstructure with the performance of the barrier layer by two-dimensional EDX mapping and three-dimensional APT. Highly effective Cu-diffusion barrier function is thus demonstrated for single-crystal TiN(001) (up to 1000 °C) and dense polycrystalline TiN (900 °C)

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Nitrides: Transition Metal Solid‐State Chemistry

Lengauer

2015

Encyclopedia of Inorganic and Bioinorganic Chemistry

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Both basic properties and properties interesting for applications of transition metal nitrides are presented in this article. Starting from crystal chemistry, bonding, and preparation, the article also briefly discusses the analytical chemistry of chemical and physical nitrogen analysis and standardization as well as thermodynamics. Portions of phase diagrams of group 4–6 transition metals with nitrogen are presented. A substantial part is devoted to the solid‐state properties because they make nitrides interesting for applications. The presentation of these properties includes hardness, thermal expansion, nitrogen diffusivity, thermal properties, electrical conductivities, superconductivities, and elastic properties. Several of these properties are given as a function of temperature and composition. A final part shows examples for application of transition metal nitrides because of their extraordinary properties. The topic of transition metal nitrides is closely connected to that of metal carbides.

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The evolution of diffusion barriers in copper metallization

Cited by 67 publications

References 17 publications

Copper diffusion into single-crystalline TiN studied by transmission electron microscopy and atom probe tomography

Copper diffusion into single-crystalline TiN studied by transmission electron microscopy and atom probe tomography

High-resolution characterization of TiN diffusion barrier layers

Nitrides: Transition Metal Solid‐State Chemistry

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