Investigation of niobium nitride and oxy-nitride films grown by MOCVD

Abstract

Niobium nitride (NbN) and niobium oxy-nitride (NbO x N y ) thin films were grown by metalorganic chemical vapor deposition (MOCVD) on Si(100) and Si(111) substrates using [Nb(N t Bu)(NMe 2 ){C(N i Pr) 2 (NMe 2 )} 2 ] [NB; t Bu = (CH 3 ) 3 C; Me = CH 3 ; i Pr = (CH 3 ) 2 CH] as a simultaneous Nb and N precursor. While NbN films were synthesized under a pure N 2 atmosphere, NbO x N y films were synthesized under N 2 –O 2 flow (N 2 :O 2 = 1–5) in the temperature range 400–600 °C, as well as by NbN deposition followed by ex-situ thermal treatments under flowing O 2 at 400–600 °C. The samples were subjected to a multi-technique characterization in order to elucidate the interplay between their structure, morphology and composition and the adopted processing parameters. Particular attention was devoted to the presence of Nb–N and Nb–O–N phases and their distribution in the films, as well as to surface oxidation phenomena. For the first time, niobium oxy-nitride coatings were obtained by CVD starting from the above precursor compound, with growth rates up to 270 Å/min on Si(111) at 600 °C. The films were characterized by a columnar-like/globular morphology when supported on Si(100)/Si(111) and revealed a higher crystallinity on the latter substrate. Surface and in-depth compositional analyses evidenced a limited carbon contamination and the Co-existence of niobium nitride, NbON and Nb 2 O 5 . In particular, the presence of the latter in the outermost sample layers was explained by oxidation phenomena occurring upon contact with the outer atmosphere.