Characteristics of an Amorphous Carbon Layer as a Diffusion Barrier for an Advanced Copper Interconnect

Abstract

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.

Comparison between Fe2O3/C and Fe3C/Fe2O3/Fe/C Electrocatalysts for N2 Reduction in an Alkaline Electrolyte

“…The performance of a composite catalyst in which these various phases exist can be improved by bonding . The representative C 1s XPS spectrum revealed sp 2 CC and sp 3 C–C bonding peaks at 284.7 and 285.5 eV, respectively, and oxygen functional groups, corresponding to C–O (286.2 eV) and CO (288.2 eV), as shown in Figure S4e,f. , The N 2 adsorption–desorption analyses were further carried out to investigate the specific surface area of catalysts (Figure S5). All catalyst samples exhibit a typical type IV curve, indicating the presence of meso-/micropores in the fabricated catalysts.…”

Use of Nanoscale Carbon Layers on Ag-Based Gas Diffusion Electrodes to Promote CO Production

“…Figure C illustrates the Raman spectrum of the as-deposited carbon layer onto the Ag-based GDE electrode before the electrochemical CO 2 reduction. As shown in the graph, one main peak appears at 1568 cm –1 and one shoulder at 1361 cm –1 , which correspond to the G (E 2g ) and D (A 1g ) bands − and are visible in all carbon samples. The D maximum originates from the movement of neighboring atoms in radial directions in the plane and is caused by structural defects, often called the disorder-induced mode.…”

“…The G maximum corresponds to the movements of atoms in opposite directions perpendicular to the plane and causes C−C bond stretching. 33,34 These two bands are typical features present in amorphous carbon materials and combined with the absence of the 2D band (at about 2700 cm −1 , characteristic to bulk or multilayer graphite/graphene-related materials) 30,35 clearly indicate that a nanoscale amorphous carbon surface layer is present at the Ag-based GDE electrode. In addition, upon increasing the carbon layer thickness, the intensity of the carbon-related maxima increased, an observation which confirms the trend already proven by the HAADF STEM experiments.…”

Large‐Area Uniform 1‐nm‐Level Amorphous Carbon Layers from 3D Conformal Polymer Brushes. A “Next‐Generation” Cu Diffusion Barrier?

“…Indeed, several studies have focused on a-C films as a promising ultrathin material. [21][22][23][24][25][26] To date, sputtering, laser-assisted CVD, CVD growth on Ge (111) substrates, and electron-beam irradiated self-assembled monolayer films, have been studied and proposed as ultrathin a-C layers. [5,[21][22][23]26] Physical vapor deposition (PVD) methods, including sputtering and e-beam evaporation from graphite, have been utilized to yield a-C layers.…”

“…[21][22][23][24][25][26] To date, sputtering, laser-assisted CVD, CVD growth on Ge (111) substrates, and electron-beam irradiated self-assembled monolayer films, have been studied and proposed as ultrathin a-C layers. [5,[21][22][23]26] Physical vapor deposition (PVD) methods, including sputtering and e-beam evaporation from graphite, have been utilized to yield a-C layers. [27][28][29] These methods commonly suffer from poor deposition uniformity when scaled down to the 1-nm-level thickness.…”