Plasma-Enhanced Atomic Layer Deposition of Low Resistivity and Ultrathin Manganese Oxynitride Films with Excellent Resistance to Copper Diffusion

Low resistivity, high conformability, and ultrathin barriers against Cu diffusion have always been a critical challenge for fabrications of extremely large-scale integrated circuits. In this article, manganese oxynitride (MON) barriers against Cu diffusion are explored by plasma-enhanced atomic layer deposition (PE-ALD) with Mn(EtCp)2 and NH3 precursors, demonstrating a growth rate of ∼0.39 Å/cycle and a root-mean-square (RMS) roughness down to 0.38 nm in the temperature range of 225–300 °C. As the deposition temperature increases from 225 to 300 °C, the atomic ratio of Mn/N in the as-deposited film increases from 1.96 to 2.7; however, the percentage of oxygen always stabilizes at 19 ± 1%, which results from the residual oxygen in the chamber. The film resistivity reduces from 3.4 × 10–2 to 5.5 × 10–3 Ω·cm and the film density increases from 5.35 to 5.61 g/cm3 with the increase of deposition temperature. Only a 2.4 nm MON film can effectively prevent Cu atoms from diffusing through it even after annealing at 550 °C for 30 min, and the failure temperature can be elevated to 650 °C for the 3.7 nm MON barrier. Further, the failure mechanism of the MON diffusion barrier is also addressed. Owing to combined advantages of ultrathin and uniform thickness, good conductivity, and excellent barrier effect, the PE-ALD MON ultrathin film is thus very promising for nanoscale copper interconnection technologies.