We have studied sputter-deposited Ta, Ta s6 't4, and Ta3&ir4N~e thin lilms as diffusion Sr barriers between Cu overlayers and Si substrates. Electrical measurements on Si n +p shallow junction diodes demonstrate that a 180-nm-thick Ta film is not an effective diffusion barrier. For the standard test of 30-min annealing in vacuum applied in the present study, the Ta barrier fails after annealing at 500 "C. An amorphous Ta74Si26 thin film improves the performance by raising the failure temperature of a (Si)/Ta7$iZ6(100 nm)/ Cu(500 nm) metallization to 650 "C!. Unparalled results are obtained with an amorphous ternary Ta36Si14N50 thin film in the Si/Ta3,&N5c(120 nm)/Cu(500 nm) and in the Si/TiSi2(30 nm)/Ta3,$iNS0(80 nm)/Cu(500 nm) metallization that break down only after annealing at 900 "C. The failure is induced by a premature crystallization of the Ta3&&, alloy (whose crystallization temperature exceeds 1000 "C) when in contact with copper.

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Films of Ti-Si-N were synthesized by reactively sputtering TiSi 2 , Ti 5 Si 3 , or Ti 3 Si targets in an Ar/N 2 gas mixture. They were characterized in terms of their composition by MeV 4 He backscattering spectrometry, their atomic density by thickness measurements combined with backscattering data, their microstructure by x-ray diffraction and high-resolution transmission electron microscopy, and their electrical resistivity by four-point-probe measurements. All films have a metal-to-silicon ratio close to that of their respective targets. The as-deposited films are either entirely amorphous or contain inclusions of TiN-like nanometer-sized grains when the overall atomic composition of the films approaches the TiN phase in the ternary Ti-Si-N diagram. A correlation between the resistivity of the as-deposited films and their position in the ternary phase diagram is evident, indicating that at the atomic scale, the spatial arrangement of atoms in the amorphous phase and their bonding character can approximate those of the equilibrium phases. A mixture of nanocrystalline TiN and amorphous Si-N is proposed for some titanium-and nitrogen-rich films. The atomic density of some films exceeds 10 23 at./cm 3 . The resistivity of the films increases with the Si and the N content. A thermal treatment in vacuum at 700°C for 1 h decreases the resistivity of the Ti-rich films deposited from the Ti 5 Si 3 or the Ti 3 Si target, but increases that of the Si-rich films deposited from the TiSi 2 target when the nitrogen content exceeds about 30 at. %. The effectiveness of these films as diffusion barriers between Si and Al or Cu is reported in Part II.

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