TaNx film is grown by plasma enhanced atomic layer deposition (PEALD) using t-butylimido tris(dimethylamido) tantalum as a metalorganic source with various reactive gas species, such as N2+H2 mixed gas, NH3, and H2. Although the pulse sequence and duration are the same, aspects of the film growth rate, microstructure, crystallinity, and electrical resistivity are quite different according to the reactive gas. Crystallized and relatively conductive film with a higher growth rate is acquired using NH3 as a reactive gas while amorphous and resistive film with a lower growth rate is achieved using N2+H2 mixed gas. To examine the relationship between the chemical properties and resistivity of the film, X-ray photoelectron spectroscopy (XPS) is conducted on the ALD-grown TaNx film with N2+H2 mixed gas, NH3, and H2. For a comparison, reactive sputter-grown TaNx film with N2 is also studied. The results reveal that ALD-grown TaNx films with NH3 and H2 include a metallic Ta-N bond, which results in the film’s higher conductivity. Meanwhile, ALD-grown TaNx film with a N2+H2 mixed gas or sputtergrown TaNx film with N2 gas mainly contains a semiconducting Ta3N5 bond. Such a different portion of Ta-N and Ta3N5 bond determins the resistivity of the film. Reaction mechanisms are considered by means of the chemistry of the Ta precursor and reactive gas species.

Insulating TaNx films were grown by plasma enhanced atomic layer deposition using butylimido tris dimethylamido tantalum and N2+H2 mixed gas as metalorganic source and reactance gas, respectively. Crossbar devices having a Pt/TaNx/Pt stack were fabricated and their electrical properties were examined. The crossbar devices exhibited temperature-dependent nonlinear I (current) - V (voltage) characteristics in the temperature range of 90-300 K. Various electrical conduction mechanisms were adopted to understand the governing electrical conduction mechanism in the device. Among them, the Poole- Frenkel emission model, which uses a bulk-limited conduction mechanism, may successfully fit with the I - V characteristics of the devices with 5- and 18-nm-thick TaNx films. Values of ~0.4 eV of trap energy and ~20 of dielectric constant were extracted from the fitting. These results can be well explained by the amorphous micro-structure and point defects, such as oxygen substitution (ON) and interstitial nitrogen (Ni) in the TaNx films, which were revealed by transmission electron microscopy and UV-Visible spectroscopy. The nonlinear conduction characteristics of TaNx film can make this film useful as a selector device for a crossbar array of a resistive switching random access memory or a synaptic device.