Copper diffusion into single-crystalline TiN studied by transmission electron microscopy and atom probe tomography
2015 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 574, 103-109 p.Article in journal (Refereed) Published
TiN/Cu bilayers were grown by unbalanced DC magnetron sputter deposition on (001)-oriented MgO substrates. Pole figures and electron back-scatter diffraction orientation maps indicate that both layers in the as-deposited state are single-crystalline with a cube-on-cube epitaxial relationship with the substrate. This is confirmed by selected area electron diffraction patterns. To study the efficiency of the TiN barrier layer against in-diffusion of Cu, we annealed samples at 900 degrees C for 1 h in vacuum and at 1000 degrees C for 12 h in Ar atmosphere. The single-crystalline structure of the TiN layer is stable up to annealing temperatures of 1000 degrees C as shown by high resolution transmission electron microscopy. While no Cu diffusion was evident after annealing at 900 degrees C, scanning transmission electron microscopy images and energy-dispersive X-ray spectrometry maps show a uniform diffusion layer of about 12 nm after annealing at 1000 degrees C for 12 h. Concentration depth profiles obtained from 3D atom probe tomography reconstructions confirm these findings and reveal that the TiN film is slightly substoichiometric with a N/Ti ratio of 0.92. Considering this composition, we propose a lattice diffusion mechanism of Cu in TiN via the formation of Cu-N vacancy complexes. The excellent diffusion barrier properties of single-crystalline TiN are further attributed to the lack of fast diffusion paths such as grain boundaries.
Place, publisher, year, edition, pages
Elsevier , 2015. Vol. 574, 103-109 p.
Titanium nitride; Copper; Diffusion; Transmission electron microscopy; Atom probe tomography
IdentifiersURN: urn:nbn:se:liu:diva-114436DOI: 10.1016/j.tsf.2014.11.084ISI: 000348044700017OAI: oai:DiVA.org:liu-114436DiVA: diva2:791879
Funding Agencies|Austrian Federal Government; Bundesministerium fur Verkehr, Innovation und Technologie; Bundesministerium fur Wirtschaft, Familie und Jugend; Styrian and the Tyrolean Provincial Government; Swedish Research Council [2013-4018]; Knut and Alice Wallenberg Foundation for the Electron Microscopy Laboratory at Linkoping University2015-03-022015-02-202016-08-31