The size of the advanced Cu interconnects has been significantly
reduced, reaching the current 7.0 nm node technology and below. With
the relentless scaling-down of microelectronic devices, the advanced
Cu interconnects thus requires an ultrathin and reliable diffusion
barrier layer to prevent Cu diffusion into the surrounding dielectric.
In this paper, amorphous carbon (a-C) layers of 0.75–2.5 nm
thickness have been studied for use as copper diffusion barriers.
The barrier performance and thermal stability of the a-C layers were
evaluated by annealing Cu/SiO2/Si metal-oxide-semiconductor
(MOS) samples with and without an a-C diffusion barrier at 400 °C
for 10 h. Microstructure and elemental analysis performed by transmission
electron microscopy (TEM) and secondary ion mass spectroscopy showed
that no Cu diffusion into the SiO2 layer occurred in the
presence of the a-C barrier layer. However, current density-electric
field and capacitance–voltage measurements showed that 0.75
and 2.5 nm thick a-C barriers behave differently because of different
microstructures being formed in each thickness after annealing. The
presence of the 0.75 nm thick a-C barrier layer considerably improved
the reliability of the fabricated MOS samples. In contrast, the reliability
of MOS samples with a 2.5 nm thick a-C barrier was degraded by sp2 clustering and microstructural change from amorphous phase
to nanocrystalline state during annealing. These results were confirmed
by Raman spectroscopy, X-ray photoelectron spectroscopy and TEM analysis.
This study provides evidence that an 0.75 nm thick a-C layer is a
reliable diffusion barrier.
Precisely controlled synthesis strategies to prepare anisotropic nanomaterials with high yield and easy operation are exceedingly in demand because hybrid structures often introduce novel properties that cannot be achieved by isotropic nanomaterials. Here, a one-pot, two-step hot injection method was developed to prepare Cu 6 Sn 5 −Sn hybrid intermetallic−metal nanoparticles with an anisotropic structure. Hybrid nanoparticles with distinguishable Sn and Cu 6 Sn 5 domains were formed under mild temperature. Different compositions of Sn and Cu 6 Sn 5 , ranging from pure Sn to various ratios of the Sn part and Cu 6 Sn 5 part to pure Cu 6 Sn 5 , were achieved by modulating the reaction conditions, the ratio of the two metals. The as-synthesized asymmetric Cu 6 Sn 5 −Sn nanoparticles show small onset potentials (0.2 V vs reversible hydrogen electrode, RHE) and high activities (1125 mA mg −1 metal at −0.2 V vs RHE) in electrocatalytic nitrate reduction reaction. Unlike reported Cu-or Sn-based catalysts in nitrate reduction, the hybrid Cu 6 Sn 5 −Sn nanoparticles selectively produce the unstable intermediate, nitrite, within a wide reduction potential window.
Focused ion beam method, which has excellent capabilities such as local deposition and selective etching, is widely used for micro-electromechanical system (MEMS)-based in situ transmission electron microscopy (TEM) sample fabrication. Among the MEMS chips in which one can apply various external stimuli, the electrical MEMS chips require connection between the TEM sample and the electrodes in MEMS chip, and a connected deposition material with low electrical resistance is required to apply the electrical signal. Therefore, in this study, we introduce an optimized condition by comparing the electrical resistance for C-, Pt-, and W-ion beam induced deposition (IBID) at 30 kV and electron beam induced deposition (EBID) at 1 and 5 kV. The W-IBID at 30 kV with the lowest electrical resistance of about 30 Ω shows better electrical properties than C-and Pt-IBID electrodes. The W-EBID at 1 kV has lower electrical resistance than that at 5 kV; thus, confirming its potential as an electrode. Therefore, for the materials that are susceptible to ion beam damage, it is recommended to fabricate electrical connections using W-EBID at 1 kV.
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