Low energy ion assisted deposition of Ta/Cu films.

A combination of molecular dynamics simulations and experiments has been used to investigate the use of various low energy ion assisted vapor deposition approaches for controlling the interfacial structures of a model copper/tantalum multilayer system. Films were grown using argon ion beam assistance with either a fixed or modulated ion energy during metal deposition. The effect of sequential ion assistance (after layer’s deposition) was also investigated. The argon ion energy was varied between 0 and 50 eV and the effect on the atomic scale structure of Ta/Cu film interfaces and the film electrical resistivity were studied. The use of simultaneous argon ion assistance with an ion energy of ∼10 eV and an ion/metal atom flux ratio of ∼6 resulted in atomically sharp interfaces with little intermixing, consistent with simulation predictions. Ion impacts in this range activated surface atom jumping and promoted a step flow film growth mode. Higher energies were also successful at interface flattening, but they caused significant intermixing between the layers and increased film’s resistivity. This could be reduced using modulated ion energy and sequential ion beam assistance. This was again consistent with atomic scale simulations, which indicated that metal layers deposited over an interface before ion assistance was initiated impeded atom exchange across interfaces and therefore intermixing. [ABSTRACT FROM AUTHOR]