Thermal and oxidation stability of Ti<i>x</i>W1−<i>x</i> diffusion barriers investigated by soft and hard x-ray photoelectron spectroscopy

Kalha, Curran; Bichelmaier, Sebastian; Fernando, Nathalie K.; Berens, Judith; Thakur, P.; Lee, T.-L.; Moreno, José Julio Gutiérrez; Mohr, Stephan; Ratcliff, Laura E.; Reisinger, Michael; Zechner, Johannes; Nelhiebel, Michael; Regoutz, Anna

doi:10.1063/5.0048304

Cited by 13 publications

(17 citation statements)

References 91 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The 4f spectrum is particularly difficult to analyze as the 4f peaks possess a narrow full width at half maximum (FWHM), but also the 5p 3/2 core line lies in close proximity to the 4 f 5/2 line, and so must be considered and included, if a peak-fit analysis is required. Additionally, if both the metal and hexavalent (VI) oxidation states are present, the 5p 3/2 metal core line overlaps with the 4f doublet peak of the W(VI) state [72]. The W 4d core level exhibits a large lifetime broadening, leading to a significant Lorentzian contribution to the line shape, which is often difficult to describe when peak fitting.…”

Section: Introductionmentioning

confidence: 99%

Lifetime effects and satellites in the photoelectron spectrum of tungsten metal

et al. 2022

Self Cite

View full text Add to dashboard Cite

Tungsten (W) is an important and versatile transition metal and has a firm place at the heart of many technologies. A popular experimental technique for the characterization of tungsten and tungsten-based compounds is x-ray photoelectron spectroscopy (XPS), which enables the assessment of chemical states and electronic structure through the collection of core level and valence band spectra. However, in the case of tungsten metal, open questions remain regarding the origin, nature, and position of satellite features that are prominent in the photoelectron spectrum. These satellites are a fingerprint of the electronic structure of the material and have not been thoroughly investigated, at times leading to their misinterpretation. The present work combines high-resolution soft and hard x-ray photoelectron spectroscopy (SXPS and HAXPES) with reflected electron energy loss spectroscopy (REELS) and a multitiered ab initio theoretical approach, including density functional theory (DFT) and many-body perturbation theory (G0W0 and GW + C), to disentangle the complex set of experimentally observed satellite features attributed to the generation of plasmons and interband transitions. This combined experiment-theory strategy is able to uncover previously undocumented satellite features, improving our understanding of their direct relationship to tungsten's electronic structure. Furthermore, it lays the groundwork for future studies into tungsten-based mixed-metal systems and holds promise for the reassessment of the photoelectron spectra of other transition and post-transition metals, where similar questions regarding satellite features remain.

show abstract

Section: Introductionmentioning

confidence: 99%

Lifetime effects and satellites in the photoelectron spectrum of tungsten metal

et al. 2022

Self Cite

View full text Add to dashboard Cite

show abstract

“…Only two reported detailed studies have explored the TiW layer using XPS, the first from Alay et al, who focused on conducting an extensive chemical and structural characterisation of TiW films using not just XPS but also X-ray diffraction (XRD), RBS, electron probe microanalysis (EPMA), and AES, 56 and the second being recent work by the authors of the present work exploring the effects of both post-deposition annealing and titanium concentration on the oxidation behaviour of TiW. 57 However, in both cases the TiW was exposed to the ambient environment, thereby forming a native and extensive surface oxide layer, not representative of the true device state. Several studies using AES have been conducted on TiW/Al 18,58 and TiW/Cu 12,22 bilayer samples, however, all rely on using in-situ sputtering to obtain elemental distribution depth profiles across the heterostructure.…”

Section: Core Levelsmentioning

confidence: 99%

“…titanium) and be the dominant component to diffuse across the metal oxide layer. 57 The second metal (i.e. tungsten) will oxidise only, if the temperature is sufficiently high or the oxygen partial pressure is high enough to induce oxidation.…”

Section: B Interfacial Oxide Formationmentioning

confidence: 99%

“…The AD and 0.5 h annealed samples show the highest level of oxygen, which in turn leads to a positive shift in the BE position of the W 4f peaks and change in line shape, both of which represent the formation of a local chemical environment of W-O bonds. 57 However, due to the low concentration of oxygen, a full, extended bulk interfacial oxide layer cannot form, evidenced by the lack of distinct chemically shifted core level peaks. As mentioned earlier, the Ti 3p core line for metallic titanium is expected to be positioned at 32.6 eV, overlapping with the W 4f 5/2 core line, and so is marked with a guide-line in Fig.…”

Section: Core Levelsmentioning

confidence: 99%

“…Due to the presence of titanium, oxidation of the TiW interface even at low residual oxygen concentrations is favourable as titanium has excellent gettering properties, 65 and a high chemical affinity towards oxygen. 57,66 The SXPS Ti 2p core level spectra are displayed in Fig. 6(c).…”

Section: Core Levelsmentioning

confidence: 99%

See 2 more Smart Citations

Evaluation of the Thermal Stability of TiW/Cu Heterojunctions Using a Combined SXPS and HAXPES Approach

Kalha,

Reisinger,

Thakur

et al. 2022

Preprint

View full text Add to dashboard Cite

Power semiconductor device architectures require the inclusion of a diffusion barrier to suppress, or at best prevent the interdiffusion between the copper metallisation interconnects and the surrounding silicon substructure. The binary pseudo-alloy of titanium-tungsten (TiW), with >70 at.% W, is a well established copper diffusion barrier but is prone to degradation via the out-diffusion of titanium when exposed to high temperatures (≥400°C). Here, the thermal stability of physical vapour deposited (PVD) TiW/Cu bilayer thin films in Si/SiO 2 (50 nm)/TiW(300 nm)/Cu(25 nm) stacks were characterised in response to annealing at 400°C for 0.5 h and 5 h, using a combination of soft and hard X-ray photoelectron spectroscopy (SXPS and HAXPES) and transmission electron microscopy (TEM). Results show that annealing promoted the segregation of titanium out of the TiW and interdiffusion into the copper metallisation. Titanium was shown be driven toward the free copper surface, accumulating there and forming a titanium oxide overlayer upon exposure to air. Annealing for longer timescales promoted a greater out-diffusion of titanium and a thicker oxide layer to grow on the copper surface. However, interface measurements suggest that the diffusion is not significant enough to compromise the barrier integrity and the TiW/Cu interface remains stable even after 5 h of annealing.

show abstract

Novel Approach for Assessing Cyclic Thermomechanical Behavior of Multilayered Structures

et al. 2022

View full text Add to dashboard Cite

Microelectronic devices require material systems combining multiple layers of material for proper operation. These inevitably have different properties, for example, the elastic modulus or the coefficient of thermal expansion. Permanently reoccurring Joule heating and successive cooling during the operation of such devices lead to high thermal stresses within the materials and even failure due to thermomechanical fatigue or delamination of layers. This is dependent on the internal stress state and the amount of plastic strain accumulated. Here, in situ thermomechanical cantilever bending experiments on a Si–WTi–Cu material system to investigate these internal stress states and their influence on deformation behavior using a novel experimental methodology are shown. During heating to , the Cu layer undergoes partial plastic deformation, which may lead to the failure of a potential device using this material combination. To assess the internal stress and strain states based on the in situ observation, a model incorporating plastic deformation and known residual stresses of layers is proposed and verified by Finite Element Analysis.

show abstract

Thermal and oxidation stability of TixW1−x diffusion barriers investigated by soft and hard x-ray photoelectron spectroscopy

Abstract: Space-charge-controlled field emission analysis of current conduction in amorphous and crystallized atomic-layer-deposited Al 2 O 3 on GaN

Cited by 13 publications

References 91 publications

Lifetime effects and satellites in the photoelectron spectrum of tungsten metal

Lifetime effects and satellites in the photoelectron spectrum of tungsten metal

Evaluation of the Thermal Stability of TiW/Cu Heterojunctions Using a Combined SXPS and HAXPES Approach

Novel Approach for Assessing Cyclic Thermomechanical Behavior of Multilayered Structures

Contact Info

Product

Resources

About