Chemical analysis of semiconductor devices using TEM energy-dispersive X-ray spectroscopy (EDS) and electron energy-loss spectroscopy (EELS)

In this paper, we discussed the challenges of chemical analysis using TEM energy-dispersive X-ray spectroscopy (EDS) and electron-energy loss spectroscopy (EELS) for semiconductor devices. In the first case study, we showed that EDS peak overlapping and Bremsstrahlung background may cause false “signals” during defect element analysis. The problem can be solved using the EDS full quantification analysis instead of the conventional raw intensity integration method. In the second example, we described how to enhance the contrast of defect mapping using EELS spectrum imaging or jump ratio method. In the third example, EELS oxygen K-edge chemical shift and energy-loss near edge structure (ELNES) were used to characterize oxidized Ta thin film deposited on SiO2. In this case, EDS technique failed because of poor energy resolution and electron beam spreading effect. In the last case, plasmons in the EELS low-loss region were used to identify different nickel silicide phases in a thin film. Other techniques such as selected area diffraction (SAD) and nano-beam diffraction (NBD) are limited by the area-selection aperture size or specimen tilting. It is also shown that non-linear least square Gaussian fitting can be used to resolve the spectrum recorded at the interface.