No abstract

No abstract

The use of an ultrathin Ru-Ta-C film as a barrier for copper metallization in sub-32-nm ultra-large-scale integration ͑ULSI͒ has been evaluated. The films, fixed at 5 nm, were deposited by magnetron sputtering using Ru and TaC targets, and the film composition and structure were adjusted by tuning the respective deposition power. The structure of the Ru-Ta-C films gradually changed from Ru 4 Ta͑C͒ to nanocrystalline or nearly amorphous when optimizing TaC. For a sandwiched scheme of Cu/Ru 82 Ta 12 C 5 /Si or Cu/Ru 77 Ta 15 C 7 /Si, the failure temperature was at least 750°C. We also electroplated Cu directly onto a Ru-Ta-C film without Cu seeding. Because of their low resistivity ͑ Ͻ 100 ⍀ cm͒ and high thermal stability, Ru-Ta-C films are promising as a Cu barrier.

Ta–Si–C amorphous films 5nm thick were found applicable as a diffusion barrier against Cu penetration for sub- 65nm integrated circuit processing. The failure mechanisms of such a barrier were still unknown and were explored in this study. Ta–Si–C films were prepared by magnetron cosputtering using TanormalSi2 and C targets on p-type Si(100) substrate. Failure mechanisms were explored by Auger electron spectroscopy, X-ray diffraction, transmission electron microscopy, and four-point probe measurement on annealed films. In a sandwiched scheme Si∕Ta–Si–C (50.3emnm)∕Cu , the failure temperatures 750 (18 atom % C) and 800°C (24 atom % C) were demonstrated. Deterioration of Ta–Si–C barriers arose from local nucleation of TanormalSi2 crystallites, providing short paths for copper penetration. Carbon addition significantly inhibited the formation of TanormalSi2 and increased the failure temperature of the barriers. From the understanding of the failure mechanism a possible solution is proposed to research thinner barriers (such as 2nm ) to meet the 2016 International Technology Roadmap for Semiconductors.

Ru-Ta-C films deposited on silicon substrates were evaluated as barriers for copper metalization. The films were prepared by magnetron cosputtering using a Ru target and a Ta-C target. Compositions and structure of resultant films were optimally tuned by the respective deposition power of each target. The fabricated Ru-Ta-C films were characterized via four-point probe measurement, x-ray diffractometry, field-emission electron probe microanalysis, and transmission electron microscopy. Failure temperature was evaluated by the sudden rise in electrical resistivity after annealing the Cu/Ru-Ta-C/Si sandwich films, and a reference bilayer Cu/(5 nm Ru)/(5 nm Ta-C)/Si scheme. The optimal compositions were 10 nm Ru 77 Ta 15 C 7 and (5 nm Ru)/(5 nm Ta-C), both of which showed failure temperature of 650°C for 30 min and electrical resistivity less than 150 lX cm. Because of their high thermal stability and low electrical resistivity, both Ru-Ta-C and Ru/Ta-C films are promising barriers for Cu metalization.