Fabrication of Ta/TaN diffusion-barrier thin films using DC magnetron sputtering

Herein, TaN thin films were deposited using direct current (DC) magnetron sputtering enhanced by side magnets. The produced TaN films were optimized to be used as diffusion barriers for backend-of-line (BEOL) microelectronics. The side magnets were strategically placed to control magnetic field distribution, enabling precise tuning of the etch-to-deposition ratios and the Ta/TaN thickness profiles. TaN films were deposited on silicon substrates at N₂ flow rates of 5–54 sccm, and they were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy, and time-of-flight secondary ion mass spectrometry (ToF–SIMS). The optimized N₂flow rates were determined to be 10–18 sccm. These flow rates along with RF bias and magnetic field control improved the step coverage and densification for high-aspect-ratio trenches. XRD and XPS revealed a transition from metallic β-Ta to cubic TaN, forming a nitrogen-rich phase with remarkable barrier properties. ToF–SIMS depth profiling indicated that the TaN layer suppressed Cu diffusion under thermal stress (345 °C; 5 min), confirming the robustness of the TaN layer in Cu–Mn/Co/Ta/TaN stacks. Integrating a side magnet with the sputtering system enhanced plasma confinement and film uniformity, thereby advancing the development of Ta/TaN deposition. These findings highlight the potential of magnetic field control in sputtering systems, offering valuable insights into diffusion-barrier technology for next-generation BEOL processes.