XPS and ARXPS investigations of ultra thin TaN films deposited on SiO2 and Si

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

doi:10.1016/j.apsusc.2005.02.025

Cited by 44 publications

(28 citation statements)

References 8 publications

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“…However, the quantification of the island formation (thickness vs. surface coverage) must be always considered critically. In a study dealing with TaN growth on SiO 2 we found discrepancies between the TaN coverage calculated from ARXPS and results from the analysis of the shape of the inelastic electron background (QUASES [12]), which we discussed as possible influence of shadowing at islands with small size and surface roughness [13]. Recent work with computer simulation of ARXPS results for small-sized islands [14] and surface roughness [15] confirm this assumption.…”

Section: Xps and Arxps Investigationssupporting

confidence: 65%

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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Section: Xps and Arxps Investigationssupporting

confidence: 65%

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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“…Nevertheless, some findings in previous experimental work indirectly pointed to similar conclusions. At growth studies of TaN on SiO 2 [9] we found with ARXPS systematically higher surface coverage than with calculations using the analysis of the background of the inelastic scattered electrons determined at one fixed angle. This effect we discussed as influence of shadowing in the ARXPS experiment.…”

Section: Introductionmentioning

confidence: 65%

Modeling of surface roughness for ARXPS

Oswald

2007

Phys. Status Solidi (c)

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PACS 68.35. Ct, 82.80.Pv Angle-resolved X-ray photoelectron spectroscopy (ARXPS) is a method for non-destructive depth profiling in the nm thickness range. For the quantification of the data, usually model calculations are used which approximate the surface structures by smooth layers. Using ARXPS data from a computer simulation, in this paper we study the influence of overlayer roughness on the quantification results. It can be followed, that rough overlayers modeled by means of small-sized islands are identified nearly as smooth layers. The effective thickness, however, can be evaluated always satisfactorily.1 Introduction The current trend to micro-scaled materials immediately leads to the demand of a highsophisticated analysis of such nm-sized features. Besides an enormous development in transmission electron microscopy, also the classical surface spectroscopic analytical methods there are still in the focus of interest. One promising method for non-destructive depth profile analysis is the angle-resolved X-ray photoelectron spectroscopy (ARXPS). The basis for the low depth information range at XPS of only some nm is the attenuation of the used signal electrons by inelastic scattering. For ARXPS the effect is used that the effective information depth can be changed by variation of the electrons take-off angle during measurement. In series of XPS measurements with angle variation, depth information about the first some nm is found, however, for quantitative interpretation always model calculations are necessary. During this process the ARXPS measurement results were compared with those from intensities calculated from an assumed model structure of the surface region. The parameters (thicknesses, stoichiometry, surface coverage) of the model structures are varied and the best approximation for calculated to experimental results is searched for. This is a complicated process because the results found are very sensitive to the model assumptions and boundary conditions used. Already a couple of years ago Cumpson [1] showed theoretically that the number of parameters that can be derived from ARXPS measurements is very limited.Because all of this, mostly simple models with smooth layers (at least with islands on top) [2-4] are used for the ARXPS quantification. However, it is quite clear that this is an incorrect assumption in many of the real cases [5]: all realistic surfaces have a roughness and may have lateral inhomogeneities. Thus it can be clearly assumed that such effects can influence the found results. In order to quantify such possible misinterpretation we decided to make computer simulations of ARXPS results for more complicated surface structures. In a recent work [6] we proposed an algorithm and showed, beside some remarks to the "magic angle concept" at overlayers on rough surfaces, in particular first results for island structures on top of smooth surfaces. It was concluded there that an overestimation of the islands surface coverage is a typical artifact when the dimensions of the islands are in t...

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“…Silicon was not detected through the TaN films according to their diffusion barrier property, especially in our case that chemical reactions with SiO 2 substrate are not expected. [11] TOF SIMS high-resolution positive mass spectra (not shown) indicate that at nominal m/z 28 N 2 + specie is predominant across the TaN films, instead at TaN/SiO 2 interface Si + becomes predominant. The Ta + , TaN + and TaO + profiles show the characteristic surface spike and signal rise at the interface with SiO 2 due to the high oxygen concentration in these two regions (matrix effect).…”

Section: Resultsmentioning

confidence: 99%

Tantalum nitride thin film resistors by low temperature reactive sputtering for plastic electronics

Scandurra

Indelli

Pignataro

et al. 2008

Surface & Interface Analysis

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This article describes the fabrication and characterisation of tantalum nitride (TaN) thin film for applications in plastic electronics. Thin films of comparable thickness (50-60 nm) have been deposited by RF-magnetron-reactive sputtering at low temperature (100• C) and their structure and physical (electrical and mechanical) properties have been correlated by using sheet resistance, stress measurements, atomic force microscopy (AFM), XPS, and SIMS. Different film compositions have been obtained by varying the argon to nitrogen flow ratio in the sputtering chamber. XPS showed that 5 : 1, 2 : 1 and 1 : 1 Ar : N 2 ratios gives Ta 2 N, TaN and Ta 3 N 5 phases, respectively. Sheet resistance revealed an increase in resistivity ongoing from the Ta 2 N phase to the Ta 3 N 5 one. The electrical properties of these films are comparable to those obtained by high temperature deposition process already reported in literature. Furthermore, a roughness and grain size modulation of the above films can be obtained by applying an RF negative bias during deposition without affecting the electrical resistivity.

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XPS and ARXPS investigations of ultra thin TaN films deposited on SiO2 and Si

Cited by 44 publications

References 8 publications

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

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

Modeling of surface roughness for ARXPS

Tantalum nitride thin film resistors by low temperature reactive sputtering for plastic electronics

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