Development of preferred orientation in polycrystalline NaCl-structure δ-TaN layers grown by reactive magnetron sputtering: Role of low-energy ion surface interactions

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We have investigated the effects of low-energy ion irradiation on texture evolution during growth of B1-NaCl-structure polycrystalline δ-TaN layers on SiO 2 by ultra-high-vacuum reactive magnetron sputter deposition at 350°C in mixed Ar+15%N 2 discharges. In parallel sets of experiments, the ion-to-metal flux ratio J i/J Ta was varied from 1.3 to 10.7 while maintaining the incident ion energy E i constant at 20 eV, and E i was varied from 8.5 to 30 eV with J i/J Ta=10.7. All TaN layers, irrespective of J i/J Ta or E i, were overstoichiometric with N/Ta=1.13±0.03. Layers grown with E i=30eV are multiphase consisting of hexagonal ε-TaN and δ-TaN, while those grown with E i≤20eV are single-phase δ-TaN. With E i=8.5eV, the δ-TaN layers have a mixed 111/002/022/113 texture, even for film thicknesses t up to 500 nm. In contrast, δ-TaN layers deposited with E i=20eV initially exhibit competitive texture evolution until a single texture dominates at t≳200nm. The preferred orientation of 500-nm-thick E i=20eV layers can be selectively and continuously varied from predominantly 111 to nearly complete 002 by increasing J i/J Ta from 1.3 to ≥ 7.4. The change in texture is primarily due to an increased steady-state atomic N coverage, resulting from collisionally induced dissociative chemisorption of incident energetic N 2+ ions, with increasing J i/J Ta. 111-oriented δ-TaN layers are underdense with both inter- and intracolumnar porosity and a tensile stress of ≃ 1.4 GPa, while 002-oriented layers are fully dense and have small compressive stresses, ≲ 0.7 GPa. © 2002 American Institute of Physics.

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