Effect of hydrogen plasma on growth of Ir thin film by plasma-enhanced hybrid atomic layer deposition

Abstract

► Growth behaviors of Ir films using hybrid ALD were investigated. ► The 3.2 nm thick Ir film was grown by hybrid ALD under 50 deposition cycles. ► The grown Ir layer exhibited typical self-limited nature of ALD. ► High conformality of 0.88 is achieved on 32 nm wide nano trench. A 3.2-nm-thick Ir layer was grown by a cyclic chemical vapor deposition (CVD)-like hybrid atomic layer deposition (ALD) method on non-patterned Si substrate and a 32-nm-wide TaN-coated nano-trench. Ir metalorganic precursors were mixed with hydrogen reactant and co-fed into the chamber in the same cycle. The Ir metalorganic precursors were effectively decomposed in the gas phase, as in a CVD process, and on the surface of the substrate, as in ALD by hydrogen plasma, which was turned on at feeding time. The nucleation density, which caused a relatively long incubation time, was considerably increased as compared to the conventional ALD process by combining the CVD process with the ALD process. The number of deposition cycles required to obtain a 3.2-nm-thick Ir film on a non-patterned Si substrate was remarkably reduced from 200 to 50 deposition cycles, resulting in a low incubation time. Furthermore, the thickness of the Ir layer increased linearly as the number of deposition cycles increased, which shows the self-limiting nature of typical ALD. The thickness of the Ir layer saturated after 10 s as the precursor injection time was increased, which is further clear evidence of the self-limited nature of ALD. The conformal deposition of Ir was performed on a 32-nm-wide, 3-nm-thick TaN-coated nano trench. The thicknesses of the Ir layer on the top, bottom, left side, and right side were measured to be 3.5, 2.9, 3.3, and 3.4 nm, respectively, as measured by HR-TEM. The calculated conformality was 0.88, which was close to the ideal value without overhang, which often occurs in PVD processes. Our study suggest that this CVD-like hybrid ALD process can be applied to prepare barrier layers with a reduced number of deposition cycles without degradation of the quality of the film, compared to those prepared by the conventional ALD process.