Electrical conductivity modulation in TaN_x films grown by plasma enhanced atomic layer deposition

TaN_x 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 TaN_x film with N₂+H₂ mixed gas, NH₃, and H₂. For a comparison, reactive sputter-grown TaN_x film with N₂ is also studied. The results reveal that ALD-grown TaN_x films with NH₃ and H₂ include a metallic Ta-N bond, which results in the film's higher conductivity. Meanwhile, ALD-grown TaN_x film with a N₂+H₂ mixed gas or sputtergrown TaN_x 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.