AES depth profiling and interface analysis of C/Ta bilayers

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Surface roughness caused by ion bombardment can influence the sputtering yield and deteriorate the depth resolution during depth profiling. In this work, the roughening of an amorphous graphite layer 60 nm thick on a Ta layer 50 nm thick deposited on a smooth silicon substrate was studied by atomic force microscopy (AFM). The AFM measurements were carried out on the surface of the as-deposited sample, and after ion-sputtering with a 1 keV ion beam at ion incidence angles of 22°, 49°and 71°in the middle of the carbon layers and at the C/Ta interfaces. Ion bombardment was performed with one and two ion beams on stationary and rotating samples with an initial surface roughness amplitude R a of 0.13 ± 0.05 nm. On stationary samples, in the graphite layer as well as at the C/Ta interface, ripple formation on the nanometre scale was found at ion incidence angles of 49°and 71°. Depending on the sputtering parameters, the wavelengths of the ripples were found to be between 18.0 ± 4.0 and 31.4 ± 4.0 nm and the amplitude between 1.0 ± 0.2 and 4.9 ± 0.2 nm, yielding a roughness parameter R a of between 0.4 ± 0.1 and 1.6 ± 0.1 nm measured over a 1 × 1 µm area. Unexpectedly, a stronger ripple formation in the graphite layer was found at a grazing ion incidence angle of 71°. The ripple formation is suppressed by sample rotation.

Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

Ripple structures developed on graphite layers during ion‐sputtering

Kovač

Zalar

Praček

2006

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“…While for pure element layers, except for the interface region, this effect can be ignored by normalizing to 100% through the layer, 21 it will be detrimental for layers consisting of two or more elements (e.g. oxides).…”

Section: Discussionmentioning

confidence: 99%

Backscattering effect in quantitative AES sputter depth profiling of multilayers

Hofmann

Wang

Zalar

2007

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AES sputter depth profiles of multilayers with constituents of very different backscattering factors show characteristic distortions in the shape of the intensity-depth profiles. These distortions are quantified by introducing an extension of the local effective backscattering factor concept developed in an earlier paper in the mixing-roughness-information depth (MRI) model for profile quantification. The extension is based on a linear superposition of two newly defined parameters, the effective backscattering factors for each interface that are diminished with distance from the respective interface by another characteristic parameter, the mean effective backscattering decay length. As shown for a Ni/C multilayer structure of six alternating layers of Ni (38 nm) and C (25 nm) on a Si substrate, AES intensity depth profiles calculated with the presented modification of the MRI model, yield an excellent agreement with the measured profile after some adjustment of the initial mean effective backscattering decay lengths and, sometimes, after a slight change of the backscattering factors given by the Ichimura-Shimizu relations. The backscattering effect is studied as a function of the single layer thickness. A critical layer thickness can be determined, below which the backscattering influence becomes negligible for typical AES depth profiling results.

“…4, the AES intensity-depth profile of carbon is shown at a C/Ta interface of the type reported by Zalar et al, 10 Fig. 4.…”

Section: Interface C/tamentioning

confidence: 96%

“…The latter three parameters are taken into account by the MRI model. 14 -16 Using the expression of Barkshire et al, 12 Zalar et al 10 first calculated the 'ideal' profile expectation assuming ideally smooth, continuous thickness reduction, and then applied the MRI model to this calculated profile to obtain the 'measured' one. This two-step procedure is cumbersome, since some more calculations are necessary to obtain the optimum MRI fit.…”

Section: Introductionmentioning

confidence: 99%

Implementing the electron backscattering factor in quantitative sputter depth profiling using AES

Hofmann

Wang

2006

Sputter depth profiling using Auger electron spectroscopy (AES) is influenced by the electron backscattering contribution to the AES intensity. When approaching an interface between two components having a different backscattering factor, the shape of the profile is characteristically distorted. This distortion is taken into account in a modified version of the mixing-roughness-information depth (MRI) model. The modification is based on the simplified assumption that the influence of the backscattering effect of the component below the interface increases exponentially with decreasing distance of the actual surface to the interface. Application of the modified MRI model is shown to yield excellent results of profile calculation for AES depth profiling of Si/W, C/Ta, C/Ti, and Au/TiO 2 interfaces, with backscattering factor ratios close to those predicted by the Ichimura-Shimizu relation. A simple correction of the backscattering influence is proposed and discussed.