AES sputter depth profiling

One of the major problems in sputter depth profiling is the progressive decrease in the depth resolution during sputtering. The depth resolution. Ar, is defined as the width of the sputtering profile required for a signal to decrease from 84% intensity to 16% intensity at a monoatomic interface, and is usually measured on model materials in which sharp interfaces are present, such as Ta Os and 

Ni/Cr multilayers. Factors known to limit the depth resolution include instrumental factors, sample characteristics and radiation-induced effects. 

In conclusion, the best materials are either amorphous, or single crystals which 

The basic limitation in depth resolution is due to the sputtering process itself  

Summary of optimized depth profiling conditions for AES/XPS (based on Ref. 78) 

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Fig. 2.27. AES sputter-depth profiles of the 0 -Al2O3-Ti thin-film structure on a smooth Si substrate covered with a TIN thin-film diffusion barrier, (A) as-deposited, (B) after heating to 500 °C, (C) after heating to 580 °C [2.147],...

Compared with XPS and AES sputter depth profiling After achieving sputter equilibrium, and until a layer with different sputtering behavior is reached [3.59], the SN flux represents stoichiometry and not altered layer concentrations evolving because of preferential sputtering effects. 

Fig. 12. Auger electron spectroscopy (AES) sputter-depth profile of CAA-treated titanium after various exposure.s in vacuum (a) as anodized, (b) 450°C for 1 h, and (c) 7(X)°C for 1 h. The sputter etch rate is 1.5 nm/min. The line indicates the original interface. The arrow denotes oxygen diffused into the substrate. Adapted from Ref. [51].

Figure 9. AES sputter depth profile from a void in a Au film plated on Pd. Sputter rate = 600A/minute.

Figure 12. AES sputter depth profiles of printed circuit boards showing the distribution of Cu in Au/Ni/Cu bonding pads with "good" and "bad" bonding.

Figure 14. AES sputter depth profiles for Ti/Si annealed in forming gas (a) and vacuum (b).

Figure 15. AES sputter depth profile for annealed Pt/Si with a native oxide on the surface of the Si.

FIGURE 9.18 AES sputter-depth profiles of the MoDTC/ZDDP and ZDDP tribofilms. 

FIGURE 6. AES sputter depth-profiles of 2024 aluminum surface before and after an FPL etch. Multiplication factors Al x 1 Mg, Cu, Ca, C x 2 O x 0.25. (From Reference 9.)... 

Table 2 shows that AES sputter depth profiles provide quantitative infonnation on elemental composition as a function of depth but are not nomially u.sed to extract chemical information. Until recently, due to the better energy resolution of the electron analyzer and to easier interpretation of spectra, chemical analysis was performed mainly by XPS. However, since the Auger transitions recorded in AES... 

AES sputter depth profile through an iron/copper/chromium multilayer structure. Each layer is 5 nm thick (Courtesy of Thermo Fisher Scientific)... 

Auger electron maps for Cr and SI Indicated that the smallest Sl/Cr ratio occurred at the pointed end of Area A. These Auger electron maps are shown In Figure 17. AES survey spectra obtained from Area B were equivalent to spectra obtained from unstressed resistors. Sputter depth profiles were obtained from both areas and they Indicated that the resistor film In Area A was only 70% as thick as the film In Area B. Sputter depth profiles obtained from an unstressed resistor were equivalent to those from Area B. The conclusion reached was that Si was diffusing away from a portion of the resistor when high currents were passed through the film. 

An almost equally valuable ability of AES/SAM is the ease by which sputter-depth profiles can be obtained. These and other methods to derive depth distribution information will be discussed in Section 3.3. In this procedure, the surface is slowly milled away by inert ion bombardment and AES is used to monitor the composition as a function of time. Although this can also be done with small spot XPS, AES is more commonly used because of its smaller analysis area which permits a smaller sputtered area and, hence, a faster sputter rate, its faster data-acquisition rate, and its compatibility with the higher pressures in the analysis chambers needed for sputtering with older models of ion guns. 

Converting the sputtering time into depth is probably one of the ino.st difficult tasks in AES/XPS depth profiling. Basically, the depth r is connected with the time t by the sputtering rate r ... 

Figure 10. Factor analysis applied to the Auger sputter depth profile of a WjN film deposited on W (a) usual AES depth profile (b) factor analysis of the W peak structure (c) factor analysis of the N peak structure.

Figure 3. Sputter depth profile, by AES. through the interface region of an adhesive joint on a phosphoric acid anodized ultrathin AI substrate. (From Ref. II.)...

The growth may be examined by the evaluation of electrochemical currents and charges taking into account the corrosion current density as described above. Other methods are based on the application of in situ ellipsometry or electrochemical quartz crystal micro-balance or of surface analytical methods working in UHV like XPS, AES, ISS, and RBS, sometimes in combination with sputter depth profiling. Examples are given in the following section. 

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