edfas.org ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 26 NO. 2 16 J = 1 to J = 3 one can find that the µSHDs of the O and Si maps overlap with each other, but the Al map shows the lowest µSHDs. As the O and Si signals come from the SiO2 dielectrics, the overlap of these two images makes sense. Unlike the O and Si maps, the Al map in Fig. 5c shows a higher density of bright dots, which aggregate and connect well to form continuous stripes on much larger scales. This explains the characteristics of its curve µSHD in Fig. 5g, that is, lower µSHD on smaller scales but much higher µSHD on larger scales. For a direct comparison, the same EDS maps under 15 keV electrons are provided in Figs. 5d to e, which are noticeably fuzzier and have inferior lateral resolution. As explained by Vanderlinde,[19] 15 keV electrons can penetrate more than 2 µm into the sample, which weakens the Al signal relative to Si because the Al lines are only 0.5 µm thick. In contrast to Si, the O signal is very short-ranged and can escape only from the near-surface area. Therefore, there will be a gap between the Si and O signals received under 15 keV EDS mapping. The µSHD curves in Fig. 5g clearly show the curve e, that is, the Si signal, exhibits the largest µSHDs on smaller scales as expected. There is now a gap between the Si and O signals. Furthermore, all the µSHD curves are above those in the 5 keV case. One of the reasons lies in the aforementioned strengthened Si signal because of deeper penetration depth, the other is due to deteriorated lateral resolution under 15 keV, which obviously expands the regions where the dielectric and metal lines are located. The above benchmark paves the way to gain data insight regarding the interrelationship amongst the µSHDs of the elemental map, electron beam energy and its penetration depth, characteristic x-rays of elements, film thickness, and lateral resolution. For specific applications, a data-driven approach can be expected to discriminate different elements according to the µSHD curves of the EDS maps. TRANSMISSION ELECTRON MICROSCOPY FIB-deposited metal films are often used for circuit editing, and the electrical resistivity of the deposited metals is of particular concern in high-speed and radiofrequency (RF) circuits. Figures 6a to f show the morphology and elemental EDS maps of two FIB-deposited platinum (Pt) films under TEM studied by DiBattista et al. This section attempts to correlate the µSHD curves of the Pt films with their electrical resistivities. By examining the µSHD curves in Fig. 6g, one can see that curve a, representing the structure shown in Fig. 6a, gradually increases its energy from J = 1 to J = 5, and then decreases its energy from J = 6 to J = 8. It is obvious that the curve ends at an Fig. 5 EDS mapping on a sample consisted of 1.25 µm width and 0.5 µm thickness Al metal lines in a SiO2 dielectric under an electron beam energy of 5 keV (a) to (c), and 15 keV (d) to (f). O K-α map in (a) and (d), Si K-α map in (b) and (e), and Al K-α map in (c) and (f). All maps are under 10,000x magnification. Images are adapted from Vanderlinde.[19] (g) The µSHD curves of the images. (a) (b) (d) (g) (c) (d) (e) (f)
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