Study of copper diffusion into Ta and TaN barrier materials for MOS devices

Copper diffusion in TaN-based thin layers

“…secondary ion mass spectrometry (SIMS) [9], transmission electron microscopy associated with energy dispersive X-ray spectrometry (TEM/EDS) [8,10], Rutherford backscattering spectrometry (RBS) [5], sheet resistance measurements [14] and X-ray diffraction (XRD) [6,[14][15][16]. These authors [6,[14][15][16] calculated Cu diffusion coefficients from onset times of Cu silicide formation for TaN, (Ti, Zr)N, TiN and TaC barriers, respectively.…”

“…They observed the formation of Cu silicide at the TaN/Si interface and calculated the Cu diffusion coefficient from the Cu concentration profiles from the surface to the Si substrate, using EDS. Loh et al [9] and Wang et al [10], calculated the Cu diffusion coefficient from the Cu penetration depth after annealing, before any TaN/Si interfacial reaction has been observed. Samples were annealed during 30 min in a standard furnace where the atmosphere is not reported [9] or in 3 Â 10 À6 Pa vacuum [10].…”

“…Loh et al [9] and Wang et al [10], calculated the Cu diffusion coefficient from the Cu penetration depth after annealing, before any TaN/Si interfacial reaction has been observed. Samples were annealed during 30 min in a standard furnace where the atmosphere is not reported [9] or in 3 Â 10 À6 Pa vacuum [10]. Analyses were investigated using SIMS [9] or high-resolution transmission electron microscopy [10].…”

“…Therefore, a diffusion barrier layer having a low electrical resistivity, in order to reduce the contact resistance, is required to prevent the copper diffusion [4]. The use of tantalum and tantalum nitride films as efficient diffusion barrier materials has received considerable interest in recent years because of their inherent properties, such as high thermal stability and electrical conductivity [5][6][7][8][9][10]. While these authors focussed on the efficiency of Ta or TaN single layers, little is reported on multilayer diffusion barriers.…”

First-principles simulations of copper diffusion in tantalum and tantalum nitride

“…On the theoretical side, research has focused on bulk properties 15 and electronic structures of TaN compounds, [16][17][18] the thermal stability of Cu/TaN/Si stacking structures, 19 and statistical modeling of atomic diffusions. 20 However, the crucial issues such as why and how TaN compounds work as diffusion barrier materials are still not well understood. Here we present comprehensive first-principles study to understand the atomistic mechanism of Cu diffusion into TaN compounds and Si substrates.…”