Characteristics of ultrathin Ta and TaN films

Thin films of TaN and Ta were examined, primarily for the scaling of their resistivity for very thin films. In the case of TaN, the material was found to be multiphase with a nitrogen composition which strongly depended on the configuration of the sputtering system and geometry, with the implication that TaN deposited in deep features was probably depleted in N. The films were mildly unstable in air and showed a strong resistive increase as the film thickness was reduced, consistent with an electron mean free path in the 20-25 nm range.