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.
Highlights
Titanium nitride (TiN), which is well known for having excellent properties such as high thermal stability, chemical inertness, and low electrical resistivity, is an attractive metallization material in the microelectronics industry.[1,2,3] TiN thin films are widely researched and employed as diffusion barrier layers, spacers, work function metals, and etch masks.[4,5,6,7,8,9] Many deposition methods have been developed to grow high quality TiN films
The electrical resistivity of reference TiN was 410 μΩ cm at 360 ○C and decreased to 320 μΩ cm at 400 ○C. This decreasing trend of electrical resistivity with increasing temperature was due to the film impurity content, preferred orientation, and crystallinity, which is well consistent with the results from other study.[31]
The results demonstrated that the activator-type atomic layer deposition (ALD) process was more effective in obtaining relatively low resistive TiN at a higher deposition temperature
Summary
Titanium nitride (TiN), which is well known for having excellent properties such as high thermal stability, chemical inertness, and low electrical resistivity, is an attractive metallization material in the microelectronics industry.[1,2,3] TiN thin films are widely researched and employed as diffusion barrier layers, spacers, work function metals, and etch masks.[4,5,6,7,8,9] Many deposition methods have been developed to grow high quality TiN films. Despite various benefits of using the ALD method for the deposition of thin films, features of ever increasing aspect ratios impose critical limitations on the mechanical stability such as bending and uniformity of the step coverage of the deposited film.[11,12] a general trend where film resistivity decreases with increasing temperature was observed in ALD.[10] Due to the stringent requirements for device fabrication, the lower resistivity of TiN formed at a low temperature is crucial to reduce RC delay, which is a significant obstacle to continued down-scaling of electronic devices.[11,13,14]
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