Advances in sputter depth profiling using AES

Dependences of the depth resolution in Auger electron spectroscopy sputter-depth profiling of a GaAs/AlAs superlattice reference material on the incident angle and energy of primary Ar + ions were investigated. The results revealed that the depth resolution is improved for the lower primary energy as a square root of the primary energy of ions at both the incident angles of 50• and 70• , except for 100 eV at 50• , where the significant deterioration of the depth resolution is induced by the preferential sputtering of As in AlAs, and the difference in the etching rate between GaAs and AlAs. The deterioration of the depth resolution, i.e. the difference in the etching rate and the preferential sputtering, observed for 100 eV at 50• was suppressed by changing the incident angle of ions from 50• to 70• , resulting in the high-depth resolution of ∼1.3 nm. The present results revealed that the glancing incidence of primary ions is effective to not only reducing the atomic mixing but also suppressing the difference in the etching rates between GaAs and AlAs and the preferential sputtering in the GaAs/AlAs multilayered system. The results also suggest that careful attention is required for the optimization of conditions of sputter-depth profiling using GaAs/AlAs superlattice materials under low-energy ion irradiation.

Section: Incident Angle Of 70supporting

confidence: 91%

Section: Incident Angle Of 70mentioning

confidence: 99%

Incident angle and energy dependences of low‐energy Ar⁺ ion sputtering of GaAs/AlAs multilayered system

Nagatomi

Bungo

Takai

2009

“…16 The ideal value of the depth resolution can be evaluated to be ¾0.7 nm using the MRI calculation by setting both the thickness of the mixing zone and the surface roughness to be the ideal value of one atomic layer of 0.3 nm. 26 The depth resolution of ¾1.1 nm obtained at the GaAs/AlAs interface with 100 eV is confirmed to be very close to the ideally expected depth resolution.…”

Section: Resultssupporting

confidence: 76%

Dependence of depth resolution on primary energy of low‐energy Ar⁺ Ions (100–1000 eV) in AES sputter depth profiling of GaAs/AlAs superlattice

Bungo

Nagatomi

Takai

2006

The dependence of the depth resolution on the primary energy of low-energy Ar + ions in Auger electron spectroscopy (AES) sputter depth profiling of an ISO reference material GaAs/AlAs superlattice was investigated for the ion incidence angle of 50°from the sample surface normal. The depth resolution was found to improve as the square root of the primary energy of the ions as the primary energy decreased from 1000 to 200 eV. In contrast, a deterioration of the depth resolution was observed at 100 eV, which was induced by the difference in the etching rates between GaAs and AlAs and preferential sputtering. Further investigation of AES sputter depth profiling under irradiation of 100-eV Ar + ions at the incident angle of 70°revealed that the difference in the etching rate and preferential sputtering could be suppressed by changing the incident angle from 50°to 70°, leading to a depth resolution of ∼1.3 nm with 100 eV. The present results confirmed that glancing incidence is effective in achieving higher depth resolution from the point of view of the reduction of not only atomic mixing but also the difference in the etching rates and preferential sputtering. Careful attention is required for optimizing conditions of low-energy ion irradiation in sputter depth profiling using the GaAs/AlAs reference material.

“…Considering this effect it is now well understood why we could neglect the backscattering effect in our former studies of Ta(7.5nm)/Si(10.5 nm) multilayers. 16 It is interesting to note that the relative backscattering effect begins to decrease with layer thickness above the maximum at 60-80 nm for the carbon layer. This is because then the maximum slope of the intensity within the layer stays constant and is independent of increasing layer thickness (as indicated by the dashed line in Fig.…”

Section: Relative Backscattering Effect and Single Layer Thicknessmentioning

confidence: 98%

Backscattering effect in quantitative AES sputter depth profiling of multilayers

Hofmann

Wang

Zalar

2007

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.