Anelasticity study on electromigration effect in Cu thin films

Abstract

Electromigration (EM) tests on Cu thin film circuits below or near 373 K with the current density between 1x10 9 A/m 2 and 8x10 9 A/m 2 were carried out by means of the composite vibrating reed method. The resonant frequency (f) and the internal friction (Q-1) of the composite reed and the resistivity (R) of the thin film circuit were measured during isothermal EM tests for as deposited Cu/Ta films, Cu/Ta films annealed at 450 K and as deposited Ta/Cu/Ta films. An increase in f, a decrease in Q-1 and a decrease in R were commonly observed. The activation energies found for the EM process (E EM) range between 0.21 and 0.41 eV for the as-deposited Cu/Ta films, between 0.21 and 0.59 eV for the annealed Cu/Ta films and around 0.3 eV for as deposited Ta/Cu/Ta films. It is suggested that a previously unrecognized mass transport process with low E EM operates in these Cu thin films.

Study of the effects of an adatom Sn on the Cu surface electromigration using a first principles method

“…That means at the same serving conditions, a super-thin-film Cu(Sn) metal line has a long EM lifetime than pure Cu. The experimental EM activation energy of Cu thin-film line ranged from 0.47 to 1.25 eV [39], the large variation in activation energy of the Cu reported in the literature were probably due to the variation in purity and microstructure of the Cu film, and the test conditions. However, according to our calculations, the diffusion barrier energy was found to be related with the surface orientation.…”

Effects of Cu Self-Capping and Ta Capping on Nanometer-Sized Cu Films Sputter-Deposited on β-Ta

“…The Cu-Ta system is a typical immiscible example; therefore, its microstructure is also of great interest from a scientific perspective. Many studies have focused on the resistivity and electromigration, [1][2][3] mechanical properties, [4][5][6] and microstructures [7][8][9][10] of Cu films formed on Ta. Interconnections between films with sizes of less than a few tens of nanometers, such as nanometer-thick Cu films on nanometer-thick Ta barrier layers, require control of their microstructures for use as strong heterogeneous filmbarrier systems.…”