Characterization of Ta and TaN diffusion barriers beneath Cu layers using picosecond ultrasonics

Thermal resistance and heat capacity in hafnium zirconium oxide (Hf1–xZrxO2) dielectrics and ferroelectric thin films

“…For the lattice heat capacity of TaN, we apply a literature value of 2.94 MJ m À3 K À1 . 39 A few observable trends in the effective thermal conductivity and thermal resistance of the Hf 1-x Zr x O 2 films emerge from Fig. 2.…”

Acoustic Waves: A Probe for the Elastic Properties of Films

“…It is nowadays implemented by femtosecond laser pulses, and is intrinsically suited to characterize thin supported films and multilayers. It follows the optical pump-and-probe scheme (Belliard et al, 2009;Bienville et al, 2006;Bryner et al 2006;Vollmann et al 2002). The pump beam, a femtosecond laser pulse, is focused, by a spherical lens, at the specimen surface and, at least partially, absorbed.…”

“…The focusing spot, a few to tens of micrometers wide, is orders of magnitude larger than the characteristic lengths of the involved phenomena: mainly the optical absorption length, and also the thermal diffusion length and the acoustic wave propagation length, both for a femtosecond time scale. Bryner et al (2006) estimate that with an aluminium surface, a near infrared laser (800 nm), and a pulse width of 70 fs, the absorption depth and therefore the dominant acoustic wavelength are of the order of 10 nm. Quite consistently, for a similar laser pulse but for Pt and Fe ultra thin films, Ogi et al (2007) estimate at several THz the upper bound of the frequencies excited by the laser pulse.…”

“…Near infrared lasers are a common choice, because at shorter wavelength more complex phenomena can occur, which were attributed to electronic interband transitions (Devos & Cote, 2004); obviously, if one is interested in elastic properties, electronic transitions are a spurious effect to be avoided. By picoseconds ultrasonics it was possible to characterize a layer stack, including a buried layer of about 20 nm thickness (Bryner et al, 2006). The uncertainty for the elastic constants of this layer is estimated at 20-25%, which is however remarkable for a layer of this type.…”

High temperature thermal properties of thin tantalum nitride films

“…9 In this analysis, we assign the carrier MFP to be equal to interatomic spacing in TaN. The relation, k p;min ¼ 1 3 C p v p k p (where C p is the volumetric heat capacity, 10 v p is the average phonon velocity, 10 and k p is the average phonon MFP calculated from TaN density 10 ), gives the minimum phonon thermal conductivity. This gives k p,min $ 1.4 W m À1 K À1 at 300 K. By summing the contribu-tions from both electrons and phonons and assuming isotropic conduction, we estimate the intrinsic thermal cross-plane conductivity of TaN at room temperature to be $4.0-4.3 W m À1 K À1 for the 50-100 nm films.…”