XPS investigations of thin tantalum films on a silicon surface

Zier, M.; Oswald, Steffen; Reiche, R.; Wetzig, K.

doi:10.1007/s00216-003-1788-2

Cited by 36 publications

(15 citation statements)

References 10 publications

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“…The fitted peak parameters and their possible chemical states are presented in Table 3. A detailed comparison of our data with those reported in literature [19,21,22] established that the as-formed h-Ta/SiO 2 interface was comprised of tantalum silicate and silicide phases. This interface was reduced during sputter depth profile analysis using Ar ions, as a result of which the tantalum silicate phase could not be observed during the sputter depth profile XPS analysis.…”

Section: Discussionsupporting

confidence: 76%

“…The accepted binding energy value for elemental Si 2p 3/2 is 99.79 eV [20] and that for fully oxidized SiO 2 (Si 4+ ) is~103.5 eV. It has been reported recently that in case of the formation of tantalum silicide (TaSi 2 ) the Si 2p peaks were shifted towards lower energies as compared to bulk elemental silicon and the Ta 4f peak was shifted towards higher binding energy by 0.5 eV as compared to the metallic tantalum [21]. We did not observe any Ta 4f peaks for TaSi 2 shifted towards higher energies.…”

Section: Discussionmentioning

confidence: 99%

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X-ray characterization of oriented β-tantalum films

et al. 2004

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Tantalum (Ta) metal films (10-70 nm) were deposited on a Si(100) substrate with a 500 nm silicon dioxide (SiO 2 ) interlayer by ion-beamassisted sputtering. The as-deposited films have been characterized by X-ray diffraction (XRD) and X-ray reflectivity (XRR) techniques. XRD measurements showed the presence of films of the tetragonal phase of tantalum (h-Ta) oriented along the (00l) plane. XRR measurements indicated the presence of graded Ta films, with a thin interface layer between the 500 nm SiO 2 layer and the Ta films. The thickness and density of this interface layer was estimated to be 1.9F0.2 nm and 10.5F0.5 g/cm 3 , respectively. X-ray photoelectron spectroscopy (XPS) was used to probe the chemical composition of this interface layer. XPS investigative studies indicated that the interface was likely composed of tantalum silicide (TaSi 2 ) and tantalum silicate (TaSiO x ). However, the TaSiO x layer was reduced during Ar ion sputter depth profile analysis. D

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Section: Discussionsupporting

confidence: 76%

Section: Discussionmentioning

confidence: 99%

X-ray characterization of oriented β-tantalum films

et al. 2004

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“…Thus one can assume that the real thicknesses for closed layers can be higher than those reported from ARXPS measurements. Investigations of Ta films on Si with sputter depth profiling also confirmed the formation of silicides at the interface Ta/Si [10,16]. However, investigations at other metal/silicon systems showed that silicide formation can also occur as the result of the energy impact from the sputter ions themselves [11,17].…”

Section: Xps and Arxps Investigationsmentioning

confidence: 89%

“…Figure 3 shows Si2p-(a) and Ta4f-spectra (b) of a series of Ta depositions with increasing Ta amount on a Si substrate [10]. An initial shift of the Ta peak was observed to higher BE with respect to metallic Ta points to silicide bonds at the interface (Fig.…”

Section: Xps and Arxps Investigationsmentioning

confidence: 93%

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Growth studies of Ta‐based films on Si with STM and XPS

Zahn

Oswald

Fülle

et al. 2007

Phys. Status Solidi (c)

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The aim of the experiments was the characterization of the first stages of film growth on silicon substrates with scanning tunneling microscopy (STM) and angle-resolved X-ray photoelectron spectroscopy (ARXPS). Thin Ta films were deposited in situ by magnetron sputtering onto Si in the thickness range from less than one monolayer up to 10 nm. The results of the experiments show a formation of tantalum silicide at the interface to the substrate. The local current-voltage characteristics obtained by scanning tunneling spectroscopy (STS) measurements show that the first stages of tantalum silicide growth are characterized by island formation. The in situ STM results are in good agreement with those of the ARXPS investigations. 1 Introduction Nowadays, copper is the material for metallic interconnects for the (ultra) large-scale integration in microelectronic devices. Because the copper diffusion into silicon must be minimized, additional diffusion barriers are necessary in such microelectronic devices using copper as wiring material. Up to now tantalum-based thin films are widely used as such barriers [1, 2] and were investigated with different experimental methods [3][4][5]. As a consequence of decreasing barrier thicknesses the knowledge of the first stages of thin film growth on the substrate is necessary [4]. Our experiments on magnetron sputtered ultra thin tantalum-based films complete the knowledge of the tantalum barrier system by results of scanning tunneling microscopy (STM) in comparison with results of X-ray photoelectron spectroscopy (XPS). This leads to additional information about the interface chemistry and the island-like film growth at the silicon substrate, because of the use of high lateral resolved STM also in its spectroscopic I(U)-mode (STS). In measurements with the constant current mode, STM provides hybrid information consisting of both the sample topography and the chemical states on the surface. The tunneling tip exactly follows the sample topography only if the sample surfaces are chemically homogeneous. The spectroscopic STS method in the scanning tunneling microscope also provides information on the sample's electronic surface state. Therefore it is possible to get local information about different chemical compounds on the surface with high lateral resolution using the measurement of the current voltage characteristics in dependence on local position on the sample. Complementary, XPS can deliver large-area information of element composition and chemical bonds at the surfaces. Investigation of surface chemistry is done with the analysis of peak shifts and/or peak shape changes of the photoelectron peaks. By additional use of the angle-resolved XPS (ARXPS) with appropriate model calculations [6,7] one can also get morphological information (film thickness, island growth) which can be compared with the STM/STS results. In this paper we will discuss the results of investigations of tantalum-based ultra thin layers deposited by reactive DC magnetron sputtering. Because of the high reactivi...

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Low‐Iridium‐Content IrNiTa Metallic Glass Films as Intrinsically Active Catalysts for Hydrogen Evolution Reaction

Wang

et al. 2019

Advanced Materials

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Although various catalytic materials have emerged for hydrogen evolution reaction (HER), it remains crucial to develop intrinsically effective catalysts with minimum uses of expensive and scarce precious metals. Metallic glasses (MGs) or amorphous alloys show up as attractive HER catalysts, but have so far limited to material forms and compositions that result in high precious‐metal loadings. Here, an Ir25Ni33Ta42 MG nanofilm exhibiting high intrinsic activity and superior stability at an ultralow Ir loading of 8.14 µg cm−2 for HER in 0.5 m H2SO4 is reported. With an overpotential of 99 mV for a current density of 10 mA cm−2, a small Tafel slope of 35 mV dec−1, and high turnover frequencies of 1.76 and 19.3 H2 s−1 at 50 and 100 mV overpotentials, the glassy film is among the most intrinsically active HER catalysts, outcompetes any reported MG, representative sulfides, and phosphides, and compares favorably with other precious‐metal‐containing catalysts. The outstanding HER performance of the Ir25Ni33Ta42 MG film is attributed to the synergistic effect of the novel alloy system and amorphous structure, which may inspire the development of multicomponent alloys for heterogeneous catalysis.

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XPS investigations of thin tantalum films on a silicon surface

Cited by 36 publications

References 10 publications

X-ray characterization of oriented β-tantalum films

X-ray characterization of oriented β-tantalum films

Growth studies of Ta‐based films on Si with STM and XPS

Low‐Iridium‐Content IrNiTa Metallic Glass Films as Intrinsically Active Catalysts for Hydrogen Evolution Reaction

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