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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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The backscattering method is employed to obtain microscopic information about solid-solid reactions of Si with thin layers (500–2000 Å) of both vacuum-evaporated Au and sputtered Pt. A remarkable observation is the migration of Si atoms into Au and Pt at relatively low temperatures (150 and 350 °C, respectively). Migration of Si in Pt induces first the formation of Pt2Si-like compounds and then PtSi. In the Au–Si system, on the other hand, Si moves through and accumulates on the Au surface in the form of SiO2 under an oxidizing heat-treatment atmosphere.