10-nm-thick quinary (AlCrTaTiZr)N film as effective diffusion barrier for Cu interconnects at 900 °C

Abstract

In this study, an ultrathin quinary nitride film (AlCrTaTiZr)N of only 10 nm thick has been developed as a diffusion barrier layer for Cu interconnects. The (AlCrTaTiZr)N nanocomposite film was constructed of nanocrystallites embedded in an amorphous matrix. At an extremely high temperature of 900 °C, the Si/(AlCrTaTiZr)N/Cu film stack remained thermally stable. Neither interdiffusion between Si and Cu through the (AlCrTaTiZr)N layer nor formation of any silicides occurred. The nanocomposite structure and severe lattice distortions attributed to the addition of multiple elements were expected as the dominant factors for the superior diffusion resistance of the (AlCrTaTiZr)N film.

Machining Performance of Sputter-Deposited (Al0.34Cr0.22Nb0.11Si0.11Ti0.22)50N50 High-Entropy Nitride Coatings

“…As long as the change in structure due to annealing is insignificant (700-900 °C), the strengthening effect is still retained. In addition, the excellent capability of high-entropy nitrides to retain the original structure at high temperatures is also reported by Huang, Lai, and Chang [26,34,35]. Annealing at 1000 °C decreases the film hardness value to 26 GPa, but this value is still higher than that of commercial TiN coatings [36].…”

High-entropy alloys: a critical assessment of their founding principles and future prospects

“…In a pure element or dilute solid solution, the potential energy associated with each lattice site is approximately equal, whereas in an HEA there will be sites in which the bonding configuration will be more preferable for a diffusing species than others, and these act as temporary traps, slowing the rate of diffusion. Others have suggested that lattice distortions are also associated with slow diffusion in HEAs, 69,181 and it seems reasonable to expect fluctuations in the potential energies of sites in a distorted lattice.…”

“…[4][5][6]8,209 This has been used to explain particular experimental observations in a number of studies. 1,52,53,55,65,69,75,100,124,166,181,205,[210][211][212][213][214] Yeh et al 5,6,8,209 have suggested that anomalously slow diffusion in HEAs originates from fluctuations in the potential energies of lattice sites that are met by diffusing species, Fig. 6.…”

“…These include their use as protective coatings owing to their good corrosion and wear resistance 1,80,84,115,170,171,[219][220][221][222][223][224][225][226][227][228][229][230][231] (see review of laser-deposited HEA coatings by Zhang et al 232 ), as alloys for bulk metallic glasses, 11,[233][234][235][236] and even as materials for hydrogen storage 237 and diffusion barriers. 1,181,182 There has also been interest in their magnetic 1,10,97,[238][239][240][241][242][243] and thermoelectric properties. 244 These properties and applications, and others, are discussed in more detail in the reviews by Zhang et al 14 and Tsai et al 6 The authors consider one of the most promising potential applications for HEAs is as structural materials, and this is addressed specifically in the following text.…”

“…175,176 Well-established models for solution strengthening have been produced for both dilute and concentrated alloys, [177][178][179] and their modification for HEAs is discussed in Section 8 of this article. A number of studies have suggested that severe lattice distortion contributes significantly to HEA properties, 3,65,75,84,85,97,165,[180][181][182][183][184][185][186] most notably with respect to increasing alloy strength, see for instance 165,187 . Importantly, however, it is apparent that the strengthening effect of precipitates may have been overlooked in some cases.…”