Low-energy ion irradiation during film growth for reducing defect densities in epitaxial TiN(100) films deposited by reactive-magnetron sputtering

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Abstract
Transmission electron microscopy has been used to study the defect structure in epitaxial TiN(100) films as a function of the growth temperature (Ts=550–850 °C) and negative substrate bias (Vs=0–500 V) applied during reactive‐magnetron sputter deposition onto cleaved MgO substrates. For the growth conditions used in these experiments, the energy per incident N ion (N+2 was the predominant ionic species) was ∼Vs/2 and the incident ion to thermal‐atom flux ratio was ∼2. The results showed that the primary defects were dislocation loops whose number density nd decreased with increasing Ts for a given Vs. However, nd decreased much more rapidly with increasing Vs at constant Ts until a minimum defect density was attained at Vs=V*s after which nd increased with further increases in Vs. Low‐energy ion irradiation during film growth played at least two primary roles: it resulted in the creation of additional point defects which then condensed into dislocation loops and it enhanced atomic mobilities thereby accelerating the rate at which defects were annealed out during deposition. The residual defect density was determined by a competition between these two effects. Films grown at Ts>750 °C and Vs=V*s were essentially free of dislocation loops. For comparison, the dislocation loop density in films grown with Vs=0 ranged from 5×1012 to 1.5×1010 cm−2 as Ts was increased from 550 to 850 °C.