Recently, nickel silicides have been used as a material for contact of the source, drain and gates in advanced complementary metal-oxide-semiconductor (CMOS) devices. Since the phase state of nickel silicides (NiSi_x) influences their resistivity, it is necessary for the development of a number of modern devices to understand the two-dimensional (2D) phase state. We demonstrate 2D mapping of nickel silicides using an energy-filtered image-series technique in a low-loss region and show the results of our analysis for phase state in CMOS devices. We prepared a test pattern for CMOS devices including contacts and gate. TEM specimens for cross-sectional observation were first prepared using an FIB system (Hitachi, FB-2100). Energy-filtered images were acquired using TEM (Hitachi, HF-2000) coupled with an energy filter (Gatan, GIF-Tridiem). The width of the energy-selecting slit was adjusted to 2 eV and the energy step between subsequent images was adjusted to 0.2 eV. The exposure time of each energy-filtered image was 5 s. The total energy range in which energy-filtered images were acquired was 20 eV, and 100 energy-filtered images were recorded. After the sample drift had been corrected between energy-filtered images, the EEL spectrum of each pixel was extracted and the maximum of the plasmon peak was determined using a least squares fit of Pseudo-Voigt function. The maximum energy was displayed as a 2D map. Using a contrast of a TEM image, we were unable to distinguish the different phase states of contacts and gate. However, the plasmon energy map showed the different phase states of contacts and gate, and we were able to identify that the gate corresponds to the NiSi phase and the contacts correspond to the NiSi₂ phase. In conclusion, this technique is indispensable for detailed failure analysis of the latest semiconductor devices, because it can be used to easily obtain a 2D map of low-loss energy regions and analyze phase states of nickel silicides.

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