Behavior of thin Ta-based films in the Cu/barrier/Si system

Abstract

This work concentrates on the diffusion barrier stability of very thin (10 or 20 nm) α- or β-Ta, TaN, Ta(O) and Ta(N,O) films in the Cu/barrier/Si system. Based on the classical theory of the thin film growth and know how of material transport in thin films, the various Ta-based films were classified according to their density of free short-circuit paths. Using scanning electron microscopy, transmission electron microscopy, glow discharge optical emission spectroscopy and secondary ion mass spectrometry, the 20 nm thin polycrystalline columnar-structured β-Ta films were found to be stable up to 500 °C for 1 h. After 1 h at 600 °C Cu3Si was formed due to short-circuit diffusion of Cu throughout the β-Ta films. The 20 nm thin giant-grained α-Ta films show equivalent performance to the β-Ta films. On the other hand, the 10 nm thin stuffed nanocrystalline face-centered-cubic (fcc) TaN films were able to protect the Si from Cu diffusion up to at least 600 °C/1 h. Ten nm thin amorphous-like Ta(N,O) and Ta(O) films also show barrier stability that is comparable to fcc TaN. While Ta(N,O) tends to recrystallize mainly into hexagonal-close-packed Ta2N above 500 °C, the Ta(O) remains amorphous even at 600 °C. Besides the amorphous-like microstructure, the high recrystallization temperature of Ta(O) is the reason why the introduction of 5 nm thin Ta(O) film into the Cu/5 nm Ta(O)/5 nm β-Ta/Si structure leads to a stability increase up to at least 600 °C for 1 h.

Co-sputtered amorphous Nb–Ta, Nb–Zr and Ta–Zr coatings for corrosion protection of cyclotron targets for [18F] production

“…The ion bombardment during deposition was shown to bring to different Ta phases dependent on the deposition system and bombarded ions kinetic energy and momentum [55][56][57]. The Ta phase formation was shown to depend also on sputtering gas [56], substrate [58,59], stress in the film [54], impurities level [60], deposition mechanics [61]. Even after a number of investigations focused on the influence of sputter deposition parameters, the mechanism of Ta phase growth is still unclear.…”

Use of novel chemical dipping method for the stability evaluation of an ultrathin TaNx barrier in Cu interconnects

“…The research and development on the use of copper thin films as an interconnect material has been growing enormously [1][2][3][4][5][6][7][8]. Many reports [9][10][11][12] say that PVD (Physical Vapor Deposition) TaN x film is an excellent diffusion barrier in spite of its limited side wall step coverage. In contrast to conventional Al/SiO 2 metallization, copper can easily diffuse into a dielectric under an electrical bias or thermal attack; hence, the coverage of a barrier layer deposited on the side wall of a damascene pattern must be crucial factor in Cu metallization.…”

Void formation in the Cu layer during thermal treatment of SiNx/Cu/Ta73Si27/SiO2/Si systems

“…Although pure tantalum fulfills a lot of requirements for diffusion barrier materials, at elevated temperatures grain boundaries within polycrystalline Ta films [1,2,3] can act as fast paths for Cu diffusion. Ta based layers with an amorphous microstructure are a promising alternative [4].…”