Stoichiometry tuning of TaN films through ion treatment: Molecular dynamics study

J Methary and R Sathiyanarayanan and R Li and PJ Stout, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A, 39, 062601 (2021).

DOI: 10.1116/6.0001251

Ion treatment of face-centered cubic and amorphous TaN films is studied using classical molecular dynamics simulations. We investigated the effect of ion type (Ne, Ar, Kr, and Xe) and its energy (50, 100, 150, and 200 eV) on the sputtering yield of Ta and N, surface stoichiometry modification (Ta/N ratio), damage cascade development and ion penetration depths in the films at 598 K temperature. We observed that the N sputtering yield is much higher than Ta in both amorphous (a-TaN) and crystalline fcc-TaN (c-TaN) films; hence, the Ta/N ratio strongly depends on the N sputtering yield. Over the energy range studied, significant surface Ta/N modification is observed when TaN films, both amorphous and crystalline, are treated with Ne and Ar rather than Kr and Xe, mainly because of comparable sizes of Ne and Ar ions to N atoms. The Ta/N ratio is found to increase monotonically with the ion energy irrespective of the ion type and crystalline nature of the film. The average penetration depth of the Ne and Ar is similar to 1.0 nm, whereas for Kr and Xe, it is similar to 0.5 nm. The penetration depth distribution shows that the collision cascade penetrates deep into the film for Ne and Ar than for Kr and Xe. The collision cascade causes surface erosion, which sputters out Ta and N from the film via secondary ion sputtering. The methodology of ion treatment employed in the present study preserves the bulk properties of the TaN film while obtaining desired stoichiometry close to the film surface. Published under an exclusive license by the AVS.

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