Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8034784 | Thin Solid Films | 2015 | 7 Pages |
Abstract
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 °C for 1 h in vacuum and at 1000 °C for 12 h in Ar atmosphere. The single-crystalline structure of the TiN layer is stable up to annealing temperatures of 1000 °C as shown by high resolution transmission electron microscopy. While no Cu diffusion was evident after annealing at 900 °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 °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.
Related Topics
Physical Sciences and Engineering
Materials Science
Nanotechnology
Authors
M. Mühlbacher, F. Mendez-Martin, B. Sartory, N. Schalk, J. Keckes, J. Lu, L. Hultman, C. Mitterer,