Effects of surface structure on depth resolution of AES depth profiles of Ni/Cr multilayers

Abstract

The influence of surface topography and crystalline structure on the depth resolution of Auger electron spectroscopy (AES) depth profiles of Ni/Cr multilayers was studied on three different samples sputter deposited onto smooth Si(111) substrates: an Ni/Cr multilayer composed of 16 alternating Ni and Cr layers with a single layer thickness of~30 nm, and the same Ni/Cr multilayer covered either with a smooth amorphous Ta 2 O 5 layer~50 nm thick or a crystalline Al layer with an average thickness of~40 nm and a relatively large average surface roughness (R a = 21.5 nm) in comparison with the first two samples (R a < 1 nm).All three types of samples were AES depth profiled with (1 rpm) and without sample rotation, using two symmetrically inclined 1 keV Ar Y ion beams at two different ion incidence angles of 47°and 80°. The AES depth profiles obtained at an ion incidence angle of 47°on stationary Ni/Cr and a-Ta 2 O 5 /Ni/Cr multilayer samples with smooth surfaces showed sharp interfaces with a depth resolution of approximately the same order of magnitude. However, due to surface microroughness induced by ion sputtering, a slight monotonous degradation of the depth resolution with sputter depth was observed on both samples. In contrast, AES depth profiling of the Al/Ni/Cr stationary sample with the initially rough crystalline Al surface layer caused in-depth topographical changes of the Ni/Cr multilayer, and the originally sharp internal interfaces were strongly broadened. The optimal depth resolution was obtained by rotational depth profiling of the samples at an ion incidence angle of~80°. The values of depth resolution were independent of the sputter depth, and were of the same order of magnitude for all three types of samples, lying between 4.5 and 8.0 nm. An atomic force microscopy study of as-deposited and selected ion-sputtered samples showed that use of a grazing incidence angle and sample rotation during AES depth profiling promoted a smoothing effect and reduced the microroughness of the initially rough sample surface.

Quantitative reconstruction of Ta/Si multilayer depth profiles obtained by Time-of-Flight-Secondary-Ion-Mass-Spectrometry (ToF-SIMS) using Cs+ ion sputtering

“…the sputtering time necessary to remove the matter corresponding to the width of one layer) is a clear indication of a decrease of the sputtering rate and cannot be taken for an increase in the depth resolution Δz [6]. The latter is directly related to the "amplitude" of the multilayer profile [7][8][9][10][11]. In contrast to conventional SIMS and GDOES, where primary ions for sputter erosion and analysis are identical, in dual-beam ToF-SIMS the sputtered volume by the Bi + ion beam used for analysis is little affected by the average sputtering rate depending on the Cs + ion beam.…”

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“…Several techniques are used to determine atomic depth profiles in coated materials. Among the most widely used, we can cite Auger electron spectroscopy [1][2][3][4] and X-ray photoelectron spectroscopy, 5,6 both using inert gas ion sputtering, and secondary-ion mass spectrometry 7,8 and glow-discharge spectroscopy [9][10][11][12] (GDS), which use ions as probes. Different limitations, in particular the restriction of sample shape or nature, narrow the application field of these techniques.…”

Numerical and experimental depth profile analyses of coated and attached layers by laser-induced breakdown spectroscopy

“…Depending on the application, different techniques such as Auger electron spectroscopy (AES) [1,2], X-ray photoelectron spectroscopy (XPS) [3,4], secondary ion mass spectrometry (SIMS) [5,6] and glow discharge optical emission spectrometry (GD-OES) and mass spectrometry (GD-MS) [7][8][9][10] are used. Different limitations, such as restriction of sample shape or nature, long time required for analysis, poor lateral resolution and etc.…”