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

We have investigated the effects of low-energy ion irradiation on texture evolution during growth of B1-NaCl-structure polycrystalline delta-TaN layers on SiO2 by ultra-high-vacuum reactive magnetron sputter deposition at 350 degreesC 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=30 eV are multiphase consisting of hexagonal epsilon-TaN and delta-TaN, while those grown with E(i)less than or equal to20 eV are single-phase delta-TaN. With E-i=8.5 eV, the delta-TaN layers have a mixed 111/002/022/113 texture, even for film thicknesses t up to 500 nm. In contrast, delta-TaN layers deposited with E-i=20 eV initially exhibit competitive texture evolution until a single texture dominates at tgreater than or similar to200 nm. The preferred orientation of 500-nm-thick E-i=20 eV layers can be selectively and continuously varied from predominantly 111 to nearly complete 002 by increasing J(i)/J(Ta) from 1.3 to greater than or equal 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 delta-TaN layers are underdense with both inter- and intracolumnar porosity and a tensile stress of similar or equal to 1.4 GPa, while 002-oriented layers are fully dense and have small compressive stresses, less than or similar to 0.7 GPa. (C) 2002 American Institute of Physics.