Tertiary alkyl halides as growth activator and inhibitor for novel atomic layer deposition of low resistive titanium nitride

Abstract

A novel atomic layer deposition (ALD) that utilizes tertiary alkyl (tert-alkyl) halides as both growth activator and inhibitor is introduced and demonstrated for the deposition of a low resistive TiN film using TiCl4 and NH3. Among the alkyl halides, tert-butyl iodide is identified as a suitable material for both growth inhibition and growth activation without any incorporation of C impurity in the film. The electrical resistivity values of TiN thin films in activator-type and inhibitor-type ALD were significantly improved by 55% and 49%, respectively. The mechanism of the reduction in electrical resistivity is elucidated by means of theoretical approach and characterizations of TiN films. For activator-type ALD, tert-butyl iodide induces in situ ligand exchange with an adsorbed Ti precursor to form Ti-I bonds, leading to an increase in the reactivity with a NH3 reactant. For inhibitor-type ALD, the improvement of film conformality in a high aspect ratio (>22:1) substrate is exhibited. This study demonstrates that the effectiveness on the use of tert-alkyl halides in ALD deposition can serve as an important guideline for future studies of the growth activator and growth inhibitor to improve film properties, making the method widely applicable.