Effect of Annealing of Titanium Nitride on the Diffusion Barrier Property in Cu Metallization

Park, Ki‐Chul; Kim, Ki‐Bum

doi:10.1149/1.2048697

Cited by 67 publications

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“…Thus, there are many reports for the Cu diffusion in TiN during the annealing even though the failure temperatures of TiN against Cu diffusion differ among researchers [6][7][8][9][10]. Generally, it was known that the grain boundaries of TiN film act as a main diffusion path of Cu or Si [8]. Therefore, to understand the temperature failure mechanisms of TiN against Cu, an investigation of the diffusivity and diffusion mechanisms of Cu in TiN thin film are needed.…”

mentioning

confidence: 99%

Grain boundary diffusion of Cu in TiN film by X-ray photoelectron spectroscopy

Lim

Lee

Chung

et al. 2000

Applied Physics A: Materials Science & Processing

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In this study, the grain boundary diffusion of Cu through a TiN layer with columnar structure was investigated by X-ray photoelectron spectroscopy (XPS). It was observed that Cu atoms diffuse from the Cu layer to the surface along the grain boundaries in the TiN layer at elevated temperature. In order to estimate the grain boundary diffusion constants, we used the surface accumulation method. The diffusivity of Cu through TiN layer with columnar structure from 400The present semiconductor devices such as ULSI require the higher integration density with smaller submicron design scheme. However, aluminum and aluminum-based metallization have some problems such as the relatively higher resistance and the failure caused by the electromigration. At present, Cu has attracted more attention as a new interconnection metallization material, because of its low resistivity (1.67 µΩ cm for bulk), and high reliability against electromigration (EM) [1,2]. However, Cu is regarded as a fatal impurity in the semiconductor fabrication process due to its high diffusivity in Si (diffusion coefficient ≈ 10 −8 cm 2 /s at room temperature) [3][4][5]. Therefore, a thin diffusion barrier preventing Cu diffusion in Si substrate is needed in order to successfully integrate Cu as an interconnecting layer.TiN is one of the most widely investigated barrier materials in Cu metallization, as well as in Al-based metallization. Thus, there are many reports for the Cu diffusion in TiN during the annealing even though the failure temperatures of TiN against Cu diffusion differ among researchers [6-10]. Generally, it was known that the grain boundaries of TiN film act as a main diffusion path of Cu or Si [8]. Therefore, to understand the temperature failure mechanisms of TiN against Cu, an investigation of the diffusivity and diffusion mechanisms of Cu in TiN thin film are needed.From the results of Chamberlain [11], the grain boundary diffusivity (D b ) and the activation energy (Q b ) of Cu in the Cu/TiN/sapphire system were 10 −17 -10 −19 cm 2 /s and 4.4 eV, respectively, at temperature region from 600 • C to 700 • C. His results indicate that TiN in Cu metallization is a better barrier system than that in Al metallization since Q b and D b of Al through TiN layer were 0.31 eV and ≈ 10 −16 cm 2 /s, respectively, from 300 • C to 550 • C [12]. Although the differences in failure temperatures and diffusion coefficients are caused by various film microstructures and characterization methods, the grain boundary diffusion coefficients of Chamberlain [11], are too different from those of Al through TiN layer. In general, the value of Q b is approximately half of that for lattice diffusion [13] and in the range of T < 1 3 T m , the smaller the measurement temperature T is, the smaller the value of Q b should be [14]. Therefore, his values of diffusion coefficient seem to be unreasonable from a view point of the grain boundary diffusion. In fact, his Q b , 4.4 eV, for Cu in TiN layer is closed to the value of the bulk (=lattice) diffusion.To study this gr...

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confidence: 99%

Grain boundary diffusion of Cu in TiN film by X-ray photoelectron spectroscopy

Lim

Lee

Chung

et al. 2000

Applied Physics A: Materials Science & Processing

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“…This can be achieved by so-called grain boundary stuffing by facilitating the formation of oxides [95][96][97][98]. However, this effect is limited to Al metallization, since the formation of Cu-oxides at the TiN grain boundaries is thermodynamically not favorable [98,99]. In addition, grain boundary stuffing leads to a resistivity increase in the TiN layer.…”

Section: Developments In Tin Diffusion Barrier Designmentioning

confidence: 99%

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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“…In the case of TiN deposition on SiO 2 , it has been reported by a number of previous au-thors that the TiN is prone to the formation of void chains along the grain boundaries. 8 These void chains are widely reported in materials growing in the so-called zone I microstructure, 9 with fine grains and a columnar structure. The observation of identical void chains in much larger grained TiN/Al demonstrates that the columnar growth is independent of the grain microstructure.…”

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confidence: 93%

Microstructure of sputtered TiN on Al

Eaglesham¹,

Bower²,

Marcus³

et al. 1997

Applied Physics Letters

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Articles you may be interested inThe influence of the growth rate on the preferred orientation of magnetron-sputtered Ti-Al-N thin films studied by in situ x-ray diffraction J. Appl. Phys. 98, 044901 (2005); 10.1063/1.1999829 Scanning magnetron-sputtered TiN coating as diffusion barrier for silicon devices Interfacial reactions in epitaxial Al/TiN(111) model diffusion barriers: Formation of an impervious self-limited wurtzite-structure AIN(0001) blocking layer

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Effect of Annealing of Titanium Nitride on the Diffusion Barrier Property in Cu Metallization

Cited by 67 publications

References 0 publications

Grain boundary diffusion of Cu in TiN film by X-ray photoelectron spectroscopy

Grain boundary diffusion of Cu in TiN film by X-ray photoelectron spectroscopy

High-resolution characterization of TiN diffusion barrier layers

Microstructure of sputtered TiN on Al

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